The 'Ligne Alpine' was the French southern component, known otherwise as the Petite Ligne Maginot (little Maginot Line), of the 'Ligne Maginot' designed and built to shield the south-eastern part of France against Italian aggression (10/25 June 1940).

By contrast with the main part of the Maginot Line in north-eastern France, the 'Ligne Alpine' perched on the Alpes Maritimes, the Cottian Alps and the Graian Alps, which offer relatively few passes suitable for any invading forces. Access was difficult for both construction and the garrisons of the 'Ligne Alpine', so the fortifications were smaller in scale than their equivalents in the main Maginot Line. The 'Ligne Alpine' was provided with only small numbers of anti-tank weapons as the terrain was mostly unsuitable for the use of armour. In 1928, the Ouvrage Rimplas was in fact the first fortification to be completed on any portion of the 'Ligne Maginot'.

In the period after the end of World War I the French governmental and military authorities studied measures to protect France’s north-eastern frontier with Germany, and a parallel effort was devoted to the south-eastern border regions, which were deemed vulnerable to Italian aggression. The Franco-Italian border was a relic of the 1860 Treaty of Turin, by which the Duchy of Savoy and the County of Nice were incorporated into France. The boundary fixed by the treaty in general followed the crest of the Alpes Maritimes inland through the Cottian Alps to the Franco-Swiss frontier to the south-east of Geneva. The newly fixed frontier left the upper reaches of many westward-draining valleys in Italian hands, which gave Italy positions on high ground overlooking French territory: the most notable of these Italian advantages was the fortress on Mont Chaberton, which threatened Briançon.

The region had been extensively fortified in the 17^th, 18^th and 19^th centuries, most notably in the late 17^th century by the great fortification expert Sébastien Le Prestre de Vauban, Seigneur de Vauban and later Marquis de Vauban, and in the late 19^th century by Raymond Adolphe Séré de Rivières, who expanded the Fort de Tournoux and other fortifications in the area as part of the Séré de Rivières system of fortifications. Passage through the Alps was possible only at a series of comparatively low passes, and movement toward the major cities of south-eastern France such as Lyon, Grenoble or Nice was possible only along a series of deep river valleys, and the French defences therefore came to be concentrated in locations such as the Bourg st Maurice in the Tarentaise facing the Little St Bernard Pass; Modane in the Maurienne facing the Mont Cenis pass; Briançon facing the Col de Montgenèvre; Barcelonnette facing the Col de Larche; the approaches to Nice from the north, with defences in the Tinée and Vésubie river valleys, around Sospel and on the Authion massif; and Menton and Nice controlling the coastal road and railway line.

In 1925 Général Charles Nollet, the French war minister, instructed Général Jean Degoutte to undertake a military survey of France’s south-eastern frontier and make recommendations for their defence. Degoutte then based his recommendation on the principle of defence in depth to economise on manpower and funds, which were needed for the main Maginot Line defences in north-eastern France. Even so, the Degoutte scheme of 1927 was still ambitious plan, and envisaged a series of fortified concrete positions on each possible frontier crossing, backed by 36 centres de résistance, each with 14 infantry casemates and 12 infantry shelters totalling about 1,000 blockhouses.

Degoutte’s proposal came under criticism by the Commission de Défense for the forward placement of the fortifications, but the overall scheme was approved by Paul Painlevé , the current war minister and a former prime minister, with a strategy of fortifying Menton, Sospel and the valleys of the Vésubie and Tinée river. Revisions late in 1927 proposed about 400 positions, but the plan was altered in 1928 at the recommendation of Général Fillonneau to concentrate the fortifications along possible axes of invasion rather than along a continuous line along the frontier. The geographic emphasis remained on Menton and Sospel, but the concept of confrontation along the frontier was replaced by a strategy of attacking the flanks of any advance by invading forces. Fillonneau was assisted by the new management organisation created to supervise the Maginot fortifications, the Commission d’Organisation des Régions Fortifiés, and the plan thus came to be based on the construction of 103 new ouvrages (blocks) and the reconstruction of 28 older fortifications.

Unlike the relatively shallow linear defences of the north-east, the revised Alpine fortifications extended some distance back from the frontier, with forward defences supported by rear defences, all constrained by the terrain into distinct sectors. A final proposal in 1930 established a scaled-down plan to be undertaken in two phases.

As with the main 'Ligne Maginot' of the north-east, the positions of the south-east took the form of concrete-encased strongpoints linked by underground tunnels, which housed living quarters, magazines and utilities. Larger ouvrages were provided with railway line of 23.6-in (600-mm) gauge for the movement of materials and munitions, but unlike those of the the north-eastern positions none of these was electrified. Because of the mountainous terrain and the vertical character of the sites chosen for fortification, individual ouvrages typically emerged from rock faces in steep hillsides or cliffs with interior galleries mined into the rock. By comparison, most north-eastern ouvrages were semi-submerged into gently rolling terrain with galleries deeply buried beneath earth cover. Many of the high-altitude petits ouvrages (small blocks) could be built only during the brief Alpine summer. This led to lengthy construction schedules, and many of these high outposts had in fact not been completed by the time of Italy’s declaration of war on 10 June 1940.

In addition to the linked complexes of blockhouses that formed the grand ouvrages and petit ouvrages, the country around and between each position was studded with isolated blockhouses, observation points, shelters (abris), outposts (avants postes) and batteries, using much the same concept of rounded concrete forms as the primary fortifications. These positions allowed the use of mobile supporting artillery, and provided rallying and control points for vital infantry support in the country between strongpoints, as the security of the border could not be based solely on subterranean fortifications. The disposition of forward outposts, backed by heavier fortifications some way to the rear, provided for defence in depth which was supported by the difficulty of the terrain.

From north to south, the 'Ligne Alpine' was organised into the Secteur Fortifié de Savoie (Savoy fortified sector) divided into two principal sections in the form of the Tarentaise valley around Bourg St Maurice and the Maurienne river valley in the area of Modane; the Secteur Fortifié du Dauphiné protecting Briançon and the Ubaye river valley opposite the Col de Larche; and the Secteur Fortifié des Alpes Maritimes covering the Tinée and Vésubie valleys and the coast in the area of Sospel and Menton. In addition, the area to the north of the principal fortifications was organised as the Secteur Défensive de la Rhône with almost no fixed fortifications as it faced neutral Switzerland.

The Alpine region was under the overall command of Général d’Armée René Olry’s Armée des Alpes with its headquarters in Valence, and this had as its primary formations the XIV Corps d’Armee in the Secteur Fortifié de Savoie and Secteur Fortifié du Dauphiné, and Général de Corps d’Armée Alfred Marie Joseph Louis Montagne’s XV Corps d’Armee in the Secteur Fortifié des Alpes Maritimes.

By comparison with the positions in north-eastern France, the Alpine fortifications made only limited use of retracting turrets, using instead concrete casemates in the sides of mountains with commanding and pre-registered fields of fire. The 'Ligne Alpine' also incorporated comparatively few artillery ouvrages, and was instead based largely on mixed-arms positions combining both artillery casemates and infantry positions. The main fortifications were supported by infantry abris of both the 'passive' (lightly armed) and 'active' (more heavily armed) types. Some of the gros ouvrages (large blocks) at the tops of mountains had aerial tramways as their primary means of access, and military roads were often build in the absence of existing ground access. All of the large positions were provided with subterranean barracks and central utility plants, and nearly all fortifications were excavated from solid rock. The depth of the overhead cover could therefore be reduced by comparison with that of the ouvrages of the north-east, which were at soil depths as great as 100 ft (30 m) the better to resist the detonation of heavy siege artillery shells. Independent means of power generation were needed in the absence of a utility distribution system, and telephone communication was also problematical, and as a result many positions used line-of-sight optical semaphores.

Also known as the Battle of the Alps, the Italian invasion of France between 10 and 25 June 1940 was the first major Italian operation of World War II and the last major undertaking of the Battle of France.

Italy’s declaration of war on France and the UK radically widened the scope of World War II in the Mediterranean and African theatres. The object of the Italy’s Fascist leader, Benito Mussolini, was the destruction of the British and French hegemony in the Mediterranean, the reclamation of all historically Italian territories and the enlargement of Italian influence in the Balkans and Africa. France and the UK had made considerable efforts throughout the 1930s to seduce Mussolini from any alliance with Germany, but the latter’s rapid successes in the first part of World War II had rendered inevitable an Italian intervention on the German side by May 1940.

Italy declared war during the evening of 10 June with effect just after 24.00. The two sides flew air raids each other on the first day of hostilities, but little took place on the Alpine front as both France and Italy had adopted a defensive posture along their common frontier. There was some skirmishing between patrols, and the French ouvrages of the 'Ligne Alpine' exchanged fire with their Italian counterparts of the 'Vallo Alpino'. On 17 June France announced that it was looking for an armistice with Germany, and on 21 June, with a Franco-German armistice on the verge of signature, the Italians launched a general offensive all along the Alpine front. This offensive was based on a primary thrust in the northern sector and a secondary thrust along the coast. The Italians drove only a short distance into French territory in the face of determined resistance, and the Italian offensive therefore stalled before attaining its primary objectives, with the seizure of the French coastal town of Menton its most significant achievement.

During the evening of 24 June, an armistice was signed at Rome, and this became effective just after 24.00 on 25 June at the same time as the Franco-German armistice. Italy was allowed to occupy the territory it had taken in the brief fighting, a demilitarised zone was created on the French side of the frontier, Italian economic control was extended into south-eastern France as fas to the west as the Rhône river, and Italy obtained certain rights and concessions in some French colonies.

During the late 1920s the Italian prime minister, Mussolini, had spoken about Italian imperial expansion, arguing that Italy needed an outlet for its 'surplus population' and that it would thus be in the best interests of other countries to accommodate this expansion. The Fascist régime’s immediate need was political hegemony in the Mediterranean, Danube basin and Balkan region, but more bombastically Mussolini aspired to an Italian empire extending from the Strait of Gibraltar to the Strait of Hormuz, such a Balkan and Mediterranean hegemony being validated, in Fascist thinking, by the Roman control of these regions in ancient times. Mussolini harboured an intent for a protectorate over Albania and for the annexation of Dalmatia, as well as military and economic domination of Yugoslavia and Greece. The Fascists also sought to establish patron/client relationships with Austria, Hungary, Romania and Bulgaria, four nations lying on the outer edges of Italy’s European sphere of influence. Though it was not among his publicly proclaimed objectives, Mussolini also wished to challenge British and French dominance of the Mediterranean as this large inland sea was seen as strategically vital to Italian interests as it was Italy’s only conduit to the Atlantic and Indian Oceans.

In 1935 Italy launched the 2^nd Italo-Abyssinian War, and in the light of a comparatively swift Italian victory this also paved the way to wildly optimistic talk of the creation of an Abyssinian army to support purely Italian forces in a conquest of Sudan, which was an Anglo-Egyptian condominium. The 2^nd Italo-Abyssinian War also characterised a an Italian shift toward a foreign policy which was more aggressive, and also 'exposed' so-called British and French vulnerabilities. As such, this paved the way to Mussolini’s attempt to realise his imperialistic goals. In 1936 the Spanish Civil War broke out, and right from the start Italy played a major part in this conflict, which lasted into 1939. The Italian military contribution was so great that it played a decisive role in the victory of the nationalist forces of General Francisco Franco y Bahamonde. Mussolini had opted for involvement in this major external war as a means of drawing Spain toward a future subservience to Italy and at the same time putting Italy on a war footing and creating what the Fascists deemed a warrior culture. The 2^nd Italo-Abyssinian War had strained relations between Italy and Germany, but the two countries' rapprochement after this conflict’s end, leading to the completion of a treaty of mutual interest during October 1936, and this was enhanced by the two countries' collaborative involvement in the Spanish Civil War. Mussolini deemed this treaty as marking the creation of a Berlin-Rome Axis around which Europe would soon revolve. It is worth noting that the treaty was also the result of increasing Italian dependence on German coal following the imposition of sanctions by the League of Nations during the 2^nd Italo-Abyssinian War, the implementation similar policies by the two countries in the Spanish Civil War, and a growing German sympathy toward Italy as a result of the European backlash to the 2^nd Italo-Abyssinian War. The aftermath of the treaty saw a major increase in the political and economic ties between Italy and Germany, and Mussolini’s steadily increasing subservience to Adolf Hitler’s influence.

During October 1938, in the aftermath of the Munich Agreement, which handed the Sudetenland region of Czechoslovakia to Germany, Italy felt strong enough to demand concessions from France. These demands included the establishment of a free port at Djibouti in French Somaliland bordering Italian-controlled Abyssinia and Eritrea, control of the railway linking Addis Ababa and Djibouti, Italian involvement in the management of Suez Canal Company, some form of Franco-Italian condominium over French Tunisia, and the preservation of Italian culture on Corsica with no French assimilation of the people. The French refused all these demands, believing that the true Italian intention was the acquisition of Nice, Corsica, Tunisia and Djibouti. On 30 November 1938, the Italian foreign minister, Conte Gian Galeazzo Ciano, addressed the chamber of deputies on the 'natural aspirations of the Italian people', and later on the same day Mussolini addressed the Fascist Grand Council on the 'immediate goals of Fascist dynamism', namely Albania, Tunisia, Corsica (an integral part of France), the Ticino (a Swiss canton), and all French territory to the east of the Var river including Nice but not Savoy.

From 1939 Mussolini frequently harped on his contention that Italy required uncontested access to the world’s oceans and shipping lanes as a means of ensuring its national sovereignty. On 4 February, for example, he addressed the Grand Council and delivered a long speech on international affairs and the goals of his foreign policy: Mussolini started by claiming that the freedom of a country is proportional to the strength of its navy, proceeded to the 'familiar lament that Italy was a prisoner in the Mediterranean', called Corsica, Tunisia, Malta and Cyprus 'the bars of this prison', and described Gibraltar and Suez as the prison guards. Mussolini continued that in order to break British control, her bases on Cyprus, Gibraltar and Malta, as well as in Egypt (controlling the Suez Canal) would have to be neutralised. On 31 March, Mussolini stated that 'Italy will not truly be an independent nation so long as she has Corsica, Bizerta, Malta as the bars of her Mediterranean prison and Gibraltar and Suez as the walls.' Fascist foreign policy took for granted that France and the UK would at some time have to be confronted, conquest of Egypt and Sudan would allow the linking of Italian North Africa and Italian East Africa into a single imperial entity, and the Mediterranean prison destroyed. Then, Italy would be able to march 'either to the Indian Ocean through Sudan and Abyssinia, or to the Atlantic by way of French North Africa'.

By a time early in September 1938, the Italian military had created its plan for the invasion of Albania, and on 7 April 1939 Italian forces landed in the country and within three days had occupied most of the nation. To the Italians, Albania was a territory providing the some of the 'living space' it required to ease its overpopulation, and also the foothold needed to launch other expansionist movements into the Balkans. On 22 May 1939, Italy and Germany signed the 'Pact of Steel' joining both countries in a military alliance. This pact was the culmination of German and Italian relations from 1936, and was not defensive in nature but rather aimed at a 'joint war against France and the UK', although the Italian leadership believed that such a war would not take place for several years. The pact made no reference to any such interval, however, and Germany proceeded with the finalisation of the 'Weiss' (i) plan for the conquest of Poland.

In September 1939 the UK imposed a selective blockade of Italy, and coal from Germany, shipped out of Rotterdam in the Netherlands, was declared contraband. Germany promised to maintain delivery by the use of trains across the Alps, and the UK offered to meet all of Italy’s coal requirements in exchange for Italian weapons. Italy could not agree to the latter terms without shattering their alliance with Germany, but on 2 February 1940 Mussolini approved a draft contract with the Royal Air Force to provide 400 Caproni aircraft before terminating the contract on 8 February. On 1 March the British announced that they would block all coal exports from Rotterdam to Italy, and in the following month the UK started to strengthen its Mediterranean Fleet to enforce the blockade. Despite French misgivings, the UK refused to make concessions for fear that anything of this nature would create an impression of weakness. From the spring of 1940 Germany supplied Italy with about one million tons of coal per month beginning in the spring of 1940: this quantity exceeded Mussolini’s demand of August 1939 that Italy receive six million tons of coal for its first 12 months of war.

On 1 September German forces invaded Poland and thereby triggered the start of World War II. Following a month of fighting, Poland had been defeated, and there then followed a period of inaction, called the Phoney War and the drôle de guerre by the French, before the Germans attacked to the west in 'Gelb' and 'Sichelschnitt' on 10 May 1940. By the end of May, the Netherlands, Belgium and Luxembourg had been overrun. On 13 May, having moved major armoured forces through the heavily forested and steep hills on the Ardennes, the Germans broke through the French front and crossed the Meuse river at Sedan. The Germans rapidly encircled the Allies' northern forces, and on 27 May the trapped Anglo-French forces began their 'Dynamo' evacuation of the continent from Dunkirk, abandoning their heavy equipment in the process. The German then continued their push toward Paris in 'Rot' (iii) and, with more than 60 divisions to the remaining 40 French divisions in the north, the Germans were able to breach the French defensive line along the Somme river by 6 June. On 9 June, the Germans entered Rouen, and on the next day the French Government abandoned Paris, declaring it an open city, and fled to Bordeaux.

On 23 January, Mussolini had delivered himself of the statement that 'even today we could undertake and sustain a…parallel war'. What Mussolini had in mind was an invasion of Yugoslavia, since on that day Ciano had met the dissident Croat leader Ante Pavelić. A war with Yugoslavia was considered likely by the end of April. On 26 May, Mussolini informed Maresciallo d’Italia Pietro Badoglio, the chief of the General Staff, and Maresciallo dell’Aria Italo Balbo, the governor of Libya and Italy’s most senior air commander, that he intended to join the German war against France and the UK so that he would have a seat at the peace table 'when the world is to be apportioned' following an Axis victory. The two marshals fruitlessly sought to dissuade Mussolini, claiming that this was unwise as the Italian military was unprepared, ground formations were not up to strength, troops lacked equipment, the empire was equally unprepared, and the merchant fleet was scattered across the globe. On 5 June, however, Mussolini told Badoglio that 'I need only a few thousand dead so that I can sit at the peace conference as a man who has fought.'

On 10 June, Ciano signalled to the Italian ambassadors in London and Paris that a declaration of war would be handed to the British and French ambassadors in Rome at 16.30 local time. The declaration of war took effect at 24.00 on 10/11 June. Italy’s other embassies were informed of the declaration shortly before 24.00. Late in the day, addressing a crowd from the Palazzo Venezia in Rome, Mussolini declared that he had taken the country to war to rectify its maritime frontiers, though the modern consensus is that Italy’s entry to World War II was opportunistic and imperialistic.

On 26 May Olry had informed the prefect of Menton, the largest town on the Franco-Italian frontier, that the town would be evacuated at night on Olry’s order. The French commander gave the order on 3 June, and in the course of the following two nights the town was evacuated in 'Mandrin'. On the evening of 10/11 June, after the declaration of war, the French troops in the south-east were ordered from their barracks into their war positions, and engineers destroyed the transport and communication links across the border with 53 tons of explosives. The French took no offensive action.

As early as 14 May, the French interior ministry had given orders for the arrest of Italian citizens known or suspected of being anti-French in the event of war. Immediately after the declaration of war, the French authorities posted bills in all towns near the frontier ordering all Italian citizens to report to the local police by 15 June. Those who reported were asked to sign a declaration of loyalty, which entailed possible future military service. The response was impressive: a majority of Italians reported, and almost all willingly signed the declaration. In Nice, more than 5,000 Italians reported within three days.

In June 1940, only five Alpine passes between France and Italy were passable by motor vehicles: the Little Saint Bernard Pass, the Mont Cenis Pass, the Col de Montgenèvre Pass, the Maddalena Pass (Col de Larche) and the Col de Tende Pass. The only other routes were the coast road and a number of mule trails.

Before September 1939, the Alpine front had been the responsibility of Général d’Armée Benoît Antoine Marie Roger Besson’s 6ème Armée, which comprised 11 divisions with no fewer than 550,000 men: this was a strength altogether greater than was needed to defend a well-fortified frontier, and during October the 6ème Armée was reduced to an army detachment (détachement d’armée), renamed the Armée des Alpes, and placed under Olry’s command. A plan for a general offensive on the Alpine front in the event of war with Italy, had been developed in August 1938 at the insistence of Général d’Armée Gaston Henri Billotte, a member of the French supreme war council, and Général Maurice Gustave Gamelin, the chief of the national defence staff and chief of the army general staff, the army was deployed for offensive operations in September 1939. Even so, Olry received orders not to engage Italian forces unless first attacked by them.

By December 1939, the Armée des Alpes had been stripped of all mobile forces for redeployment to the north against the German threat, and Olry’s general staff had also been severely trimmed. This left Olry with three Alpine divisions, some Alpine battalions, the Alpine fortress demi-brigades,and two demi-brigades of chasseurs alpins with an overall strength of between 175,000 and 185,000 men. Of this number, only 85,000 men were based on the frontier: 81,000 men in 46 battalions supported by 65 groups of artillery facing Italy, and 4,500 men supported by three groups of artillery facing Switzerland. Olry’s remaining strength comprised B-series reserve divisions with second-line troops, largely reservists in the age bracket between 40 and 50. B-series divisions had only a low priority for new equipment and were also only poorly trained during their years of reserve commitment. However, the Armée des Alpes possessed 86 sections d'éclaireurs-skieurs, which were platoons of 35 to 40 elite troops trained in and equipped for mountain warfare, skiing and mountain climbing.

On 31 May, the Anglo-French Supreme War Council decided that, in the event of an Italian declaration of war, a programme of air attacks should be launched against industrial and oil-related targets in northern Italy. To facilitate this, the French allotted to the Royal Air Force the use of two airfields, in the area to the north of Marseille, as forward refuelling and operational bases for bombers flying from the UK. The headquarters of No. 71 Wing, or 'Haddock' Force, arrived at Marseille on 3 June, and this flew Armstrong Whitworth Whitley and Vickers Wellington medium bombers of Nos 10, 51, 58, 77, 102 and 149 Squadrons. The French themselves reserved part of the Armée de l’Air in preparation for Italy’s possible entry into the war. These units formed the Zone d’Opérations Aériennes des Alpes (Aerial Operations Zone of the Alps) with its headquarters at Valence-Chabeuil airport. Fortunately for the French, Italian military intelligence had grossly overestimated the number of aircraft still available in the Alpine and Mediterranean theatres by 10 June, when many had in fact been withdrawn to face the German invasion. The actual numbers in the ZOAA were 70 fighters, 40 bombers and 20 reconnaissance craft, with a further 28 bombers, 38 torpedo bombers and 14 fighters of the Aéronavale (naval aviation) and three fighters and 30 other aircraft on Corsica. Italian reconnaissance had put the number of French aircraft at a figure of more than 2,000 and of the British at more than 620 in the Mediterranean. Italian military intelligence also reported the strength of the Armée des Alpes at 12 divisions, although it had only six such formations by June.

During the years between the world wars, the strength of the Italian military had fluctuated in a major fashion reflecting waves of mobilisation and demobilisation. By the time Italy entered the war, more than 1.5 million men had been mobilised, and the Italian army had formed 73 divisions out of this manpower. Only 19 of these divisions were complete and fully combat ready, however, while another 32 were in various stages of formation and could be used for combat if needed, while the rest were unready for operations.

In the event of war, Italy was prepared to adopt a defensive stance on both the Italian and Yugoslav fronts, for defence against French aggression and/or an offensive against Yugoslavia should France remain neutral. There was no planning for an offensive against France beyond mobilisation, and along the Italo-French frontier 300,000 men were massed in 18 infantry and four alpine divisions. These formations were deployed defensively, mainly at the entrance to the valleys and with their artillery disposed to engage to strike at targets inside the border in the event of an invasion. The Italians were thus in no way prepared to assault French fortifications, and their deployment did not change before June 1940. The Italian formations constituted Generale d’Armata Principe Umberto di Savoia’s Gruppo Armate Ovest with General d’Armata Pietro Pintor’s 1a Armata of three corps with 13 divisions and a number of smaller units, and Generale di Corpo d’Armata Mario Vercellino’s 4a Armata of three corps with nine divisions and a number of smaller units at the front and Generale di Corpo d’Armata Emanuele Filiberto Duca di Pistoia’s 7a Armata in reserve at Turin, and a further 10 mobile divisions in two corps of Generale d’Armata Ettore Bastico’s Armata di Po (later 6a Armata) were also made available to the Gruppo Armate Ovest. Most of these latter divisions were still mobilising, however, and were therefore not yet ready for battle.

Supporting the Gruppo Armate Ovest were 3,000 pieces of artillery and two independent armoured regiments. After the campaign had started, additional armoured support was provided by the arrival of Generale di Brigata Gervasio Bitossi’s 133a Divisione corazzata 'Littorio', bringing the total number of tanks deployed to some 200. The 133a Divisione corazzata had received 70 of the new M11/39 medium tank shortly before the declaration of war, but most of the Italian armour comprised the very poor L3/35 tankette.

Although they had the numerical superiority, the Italian forces were beset by several problems. During the 1930s, for example, the army had developed an operational doctrine of rapid mobile advances backed by heavy artillery. Starting in 1938, Generale d’Armata Alberto Pariani launched a series of reforms which started a radical alteration of the army. By 1940, all Italian divisions had been converted from triangular to binary form: rather than three infantry regiments, each division now had two such regiments, bringing its total manpower strength to some 7,000, and was thus small than its French counterpart. The number of pieces of artillery had also been reduced, each division having only a single artillery regiment whereas their contemporary counterparts in other armies had three or four such regiments. Pariani’s reforms also promoted the concept of frontal assault to the exclusion of other tactical doctrines. Additionally, army front commanders were forbidden to communicate directly with their aeronautical and naval counterparts, rendering impossible any effective inter-service co-operation.

Maresciallo d’Italia Rodolfo Graziani, the chief of the army general staff, had complained that for lack of adequate motor transport, the Italian army would be unable to undertake mobile warfare as had been envisaged and now demonstrated by the Germans. The Italian army’s matériel problems also extended to manny of the standard items of equipment. In overall terms, therefore, the Italian troops were poorly equipped and such equipment as they did have was technically inferior to that in French service. After the invasion had begun, a circular advised that troops were to be billeted in private homes where possible because of a shortage of tent flies. The great majority of Italy’s armour comprised L3/35 tankettes, mounting only a machine gun and protected by armour so thin that it could not prevent the penetration of machine gun rounds. The L3/35 was completely obsolete by 1940, and this problem was compounded by a high level of engine failures, some 70% of them resulting from inadequate driver training. The same issue extended to the artillery. Only 246 pieces, out of the army’s entire arsenal of 7,970 guns, were modern. The rest were as much as 40 years old and included many weapons taken as reparations, in 1918/19, from Austria-Hungary.

The Regia Aeronautica possessed the world’s third largest fleet of bombers in June 1940. A potent symbol of Fascist modernisation, it was the most prestigious of Italy’s service branches, as well as the most recently battle-experienced as it had been heavily committed in the Spanish Civil War. The 1a Squadra Aerea, based in northern Italy, was the most powerful and best equipped of Italy’s squadre aeree (air squadron), and was responsible for supporting operations on the Alpine front. (Italy operated four geographically based squadre aeree and one zona aerea [aerial zone] covering the peninsula and Sicily. Each squadra aerea was composed of several stormi comprising gruppi each of two squadriglie. Each stormo typically operated only one type of aeroplane.)

The Italian aerial defences were weak. As early as August 1939 Italy had requested from Germany 150 batteries of 3.465-in (88-mm) anti-aircraft guns, a request renewed in March 1940 but refused on 8 June. On 13 June, Mussolini offered to send one Italian armoured division to serve on the German front in France in exchange for 50 anti-aircraft batteries, but this offer was refused.

On 29 May, Mussolini convinced the king, Vittorio Emanuele III, who was constitutionally the supreme commander of the Italian armed forces, to delegate his authority to Mussolini, and on 4 June Badoglio, latterly the chief of the supreme general staff, was already referring to Mussolini as the supreme commander. On 11 June the king issued a proclamation naming Mussolini 'supreme commander of the armed forces operating on all fronts': this was a proclamation rather than a royal decree, and therefore lacked legal force. Technically, it also restricted Mussolini’s command authority to forces in combat, but this was a distinction which was completely impractical. On 4 June, Mussolini issued a charter outlining a new responsibility for the Stato Maggiore Generale (supreme general staff), namely the transformation of his strategic directives into actual orders for the service chiefs. On 7 June the Superesercito (army supreme command) ordered the Gruppo Armate Ovest to maintain 'absolute defensive conduct both on land and [in the] air', casting into doubt Mussolini’s comment to Badoglio about a few thousand dead. Two days later, the Stato Maggiore del Regio Esercito (army general staff) ordered the Gruppo Armate Ovest to strengthen its anti-tank defences. However, no attack was yet planned or ordered for the following day, when Italy was to enter the war.

As the army chief-of-staff, Graziani travelled to the front to assume the general direction of the war after 10 June. He was joined by the under-secretary of war, Generale di Corpo d’Armata Ubaldo Soddu, who had no operational command experience, but who served as Mussolini’s connection to the front and was appointed deputy chief of the supreme general staff on 13 June. Graziani’s adjutant, Generale di Corpo d’Armata Mario Roatta, remained in Rome to transmit the orders of Mussolini, checked slightly by Badoglio, to the front. Many of Roatta’s orders were quickly countermanded by Graziani. Graziani kept all the minutes of his staff meetings during June 1940 in order to absolve himself and condemn both subordinates and superiors should the offensive fail, as he expected it would.

In the first air raids after the Italian declaration of war, Savoia-Marchetti SM.79 medium bombers of the 2a Squadra Aerea, operating from bases on the islands of Sicily and Pantelleria, were escorted by fighters as they launched two attacks on Malta during 11 June, beginning the long siege of that British island which lasted to November 1942. The first attack, delivered during the morning, involved 55 bombers, but Malta’s anti-aircraft defences reported an attack of between five and 20 aircraft, which opens the possibility that the majority of the bombers failed to find the target. The attack during the afternoon involved 38 aircraft. On 12 June a number of SM.79 bombers from Sardinia attacked French targets in northern Tunisia and, on 13 June, 33 SM.79 bombers of the 2a Squadra Aerea bombed Tunisian airfields. On the same day Fiat BR.20 bombers and Fiat CR.42 fighter-bombers of the 1a Squadra Aerea on bases in northern Italy made the first attacks on metropolitan France, bombing the airfields of the ZOAA, while the 3a Squadra Aerea operating from bases in central Italy targeted shipping off the Mediterranean coast of France.

Immediately after the declaration of war, 'Haddock' Force began to prepare its first raid on Italy. In order to prevent the possibility of Italian retaliatory raids, however, the French blocked the runways and prevented the Wellington bombers from taking off, but this failed to deter the British. On the night of 11 June, 36 Whitley bombers took off from bases in Yorkshire in order to bomb targets in Turin, the industrial heart of Italy, and refuelled in the Channel Islands. Most of the aircraft were forced to divert as a result of icing conditions and turbulence over the Alps, but during the early hours of 12 June, 10 bombers attacked Turin and two others bombed Genoa. The Italians failed to detect the raid until it was over. The airfield at Caselle misidentified the bombers as Italian aircraft from Udine and turned on the landing lights for them. At Turin the air raid alarm was not raised until the unmolested Whitley bombers had departed. The results of the action were unimpressive, however, totalling 15 civilians killed but no industrial target damaged.

On 15 June, the French finally permitted 'Haddock' Force to operate from southern France, and during the evening of that day eight Wellington bombers took off to attack industrial targets in Genoa. As a result of thunderstorms and target-location problems, only one aeroplane attacked the city during the early hours of the next day as the others returned to base. On the night of 16/17 June, 'Haddock' Force undertook its last sorties. Nine Wellington bombers took off to bomb targets in Italy, although only five managed to find their objectives. After this, the deteriorating military situation in France led to the withdrawal of 'Haddock' Force’s 950 men by ship from Marseille: the British equipment and stores were abandoned.

From bases in French North Africa, bombers of the Armée de l’Air attacked Cagliari and Trapani on 22 June and Palermo on the following day: some 20 civilians were killed at Trapani and 25 at Palermo. These were the most severe French bombings of Italian soil, and targeted sites which were strategically irrelevant. Moreover, many French bombers had recently been withdrawn from France in the face of the German advance, and more than 600 aircraft had been assembled in French North Africa by 22 June, when Général Charles August Paul Noguès, the commander-in-chief of the French forces in North Africa, requested permission to undertake offensive operations against Italy or Libya, but was initially refused.

On 15 June, the 3a Squadra Aerea despatched a force of SM.79 bombers and Fiat G.50 fighters to bomb targets on Corsica and, on 16 June, some Breda Ba 88 attack aircraft to strafe some of the same island’s airfields. The most intense air combat of the campaign took place over southern France on 15 June, when Italian BR.20 bombers and CR.42 fighters were engaged by French Dewoitine D.520 and Bloch MB.151 fighters: the Italians lost one BR.20 and several CR.42 aircraft, and the French also lost a number of aircraft. On 17 June, the Italians bombed the centre of Marseille, killing 143 persons and wounding another 136, and on 21 June bombed the port area of the same city in a daylight raid and a subsequent night raid. Air combats also took place over Tunisia, each side claiming kills. On 17 June, some Cant Z.506B floatplanes of the 4a Zona Aerea in south-eastern Italy joined a number of SM.79 warplanes for a bombing raid on Bizerte in Tunisia. The last Italian aerial operations against France were undertaken on 19 June by aircraft of the 2a and 3a Squadre Aeree against targets in Corsica and Tunisia. On 21 June, nine Italian bombers attacked the French destroyer Malin, but failed to score any hit. On the night of 22/23 June, 12 Savoia-Marchetti SM.81 bombers from Rhodes in the Italian Dodecanese islands group in the south-eastern part of the Aegean Sea made the first attempt to bomb the British naval base in Alexandria on the north coast of Egypt, and one of these bombers ran out of fuel during the return flight and was forced to ditch in the sea.

During the Italian general offensive between 21 and 24 June, the Regia Aeronautica bombed the fortifications of the 'Ligne Alpine' little or no real effect. According to Generale di Squadra Aerea Giuseppe Santoro, the deputy chief of the Italian air staff, this effort was pointless as the French defensive works were designed to withstand heavy shelling and largely buried in the the sides of rocky mountains. He added that poor maps, fog and snow made target identification difficult, and that aircrews had not been trained for such operations, which had not even been considered before the start of the campaign. Only 115 out of 285 Italian bomber sorties between 21 and 24 June actually managed to locate their targets, and then released only 78.75 tons of bombs. During the morning of 23 June, Italian pilots looking for the French artillery position at Cap Martin, which was engaging Italian troops in Menton, accidentally bombed their own artillery on Capo Mortola, some 6.25 miles (10 km) from their intended target. The Armée de l’Air in southern France took no part in the defence of the 'Ligne Alpine'. instead concentrating their efforts on defence of its airfields against Italian attacks. Accounts of Italian aircraft strafing columns of refugees on the road from Paris to Bordeaux, however, are fictions. On no occasion did the Regia Aeronautica extend its reach beyond Provence in June 1940, and attacked only military sites.

During 12 June, French SES groups had crossed the border and started to skirmish with Italian units in the Maddalena Pass. An Italian outpost was surprised, resulting in the death of an Italian non-commissioned officers and the wounding of two soldiers. The Italian defensive attitude changed with the collapse of the French administration of Prime Minister Paul Reynaud on 15 June. Since Reynaud’s successor, Maréchal de France Henri Philippe Benoni Omer Joseph Pétain, was known to favour the reaching of an accommodation with Germany, Mussolini quickly decided that Italy must make territorial gains before a Franco-German armistice could be agreed and signed. On the same day, therefore, he instructed the Gruppo Armate Ovest to prepare an offensive which could be launched in three days. This was an altogether impractical demand for any offensive undertaking of a major nature. Badoglio responded that the conversion of the Italian posture from a defensive to an offensive disposition would in itself require no fewer than 25 days. The Stato Maggiore Generale therefore revised Mussolini’s instruction into two directives: the first permitted Italian incursions into French territory, while the second abrogated the staging plan then in force, namely 'P.N.12', and ordered the Gruppo Armate Ovest to prepare to take advantage of the possible collapse of the Armée des Alpes.

On 17 June Pétain announced that 'It is with a heavy heart that I tell you today that we must stop fighting.' This suggested to the Italians that the Armée des Alpes was on the point of dissolution, if not already in the process of collapse. The Stato Maggiore Generale also came to the conclusion, on the basis of no evidence at all, that the German advance in the Rhône river valley would force the French to start the evacuation of their Alpine forts. In an order to his formation on 18 June, Generale di Divisione Paolo Micheletti of the 1a Divisione alpina 'Taurinense' advised that 'a strong resistance cannot be anticipated, owing to the shaken morale [of the French].' Micheletti was more worried about the bands of armed fuoriusciti (Italian political exiles) rumoured to be in the area than about the French.

On 16 June Mussolini had issued the order for the start of offensive operations within 10 days. Three undertakings were planned: Operazione 'B' through the Little Saint Bernard Pass, Operazione 'M' through the Maddalena Pass and Operazione 'R' along the riviera. On the same day, elements of the 4a Armata attacked in the area of Briançon. As the Italians advanced, the French holding the Fort de l’Olive began to shell the Italian Fortezza Bardonecchia, and in retaliation the 149-mm (5.87-in) guns of the Italian fortress on Monte Chaberton were trained on the Fort de l’Olive. The Italian bombardment silenced the French fort in the course of the following day. On 18 June, the guns of Fortezza Chaberton, which dominated the Col de Montgenèvre, engaged the small French Ouvrage Gondran, near Briançon, with artillery fire in support of the Italian ground advance. The Italian fire inflicted little damage on the French fort, but did exercise a powerful effect on the French morale.

During the day, the Gruppo Armate Ovest received two seemingly contradictory orders that 'the hostilities against France have to be suspended immediately', and that 'the preparation for the previously announced…operations should continue at the same pace'. The true intent of these orders is still unclear, but as word of them disseminated through the Italian ranks many began to rejoice in the apparent end of the war and even to fraternise with the French. Commanders at the front were ordered to explain the situation correctly to their troops: hostilities would eventually be resumed.On the same day Mussolini met Hitler in Munich, where the Italian leader was informed that his claims to Nice, Corsica and Tunisia were interfering with the Franco-German armistice negotiations. The implication was clear: the Italian claims had to be backed by military success if the Italians wanted German support in their claims.

Before the Italian declaration of war, the British and French had planned a sortie by ships of the Royal Navy and Marine Nationale into the Mediterranean with the express intent of provoking the Regia Marina into battle: the British were to despatch Admiral Sir Andrew Cunningham’s Mediterranean Fleet toward Malta in a sweep also designed to evaluate the effectiveness of the Italian air and submarine forces, and the French to despatch the Flotte de la Mediterranée to undertake shore bombardments in the Gulf of Genoa, the Tyrrhenian Sea, along the coasts of southern Italy, Sicily and the Dodecanese islands group. The Allied fleets possessed a 12/1 capital ship advantage over the Italians in the Mediterranean, and in overall terms on 10 June, the Allied and Italian navies were disposed as follows: the UK disposed of 62 combat surface ships and 12 submarines, the French 78 surface ships, in addition to six torpedo boats and 40 submarines, and the Italians 83 surface ships, 138 torpedo boats and 113 submarines. Ammiraglio d’Armata Domenico Cavagnari, the Italian navy’s chief-of-staff, held a strategic view opposed to the standard concept of a decisive battle between the opposing fleets: he preferred the idea of using the surface forces to mine the Sicilian Channel while deploying his submarines en masse to seek out and engage Allied warships, thereby degrading their overall numerical superiority.

As events panned out, the rapid progress of the German armies through France meant that the naval offensive envisaged by the Allies against Italy was not undertaken. Nonetheless, there were a number of smaller undertakings: for example, four French cruisers supported by three destroyers undertook a sweep in the Aegean Sea during the opening days of the war with Italy while much of the French submarine fleet put to sea, but the British instead of launching a sortie toward Malta, confined themselves largely to the coast of North Africa and attempted interceptions of Italian vessels delivering supplies and reinforcement to Libya.

On 12 June, elements of Vice-amiral Marcel Gensoul’s Force de Raid, based at Mers el Kébir in Algeria, sortied in response to a report of German warships entering the Mediterranean from the Atlantic. The report turned out to be incorrect, and the French force was sighted by the Italian submarine Dandolo which fired, without success, on the light cruisers Jean de Vienne, Galissonnière and Marseillaise. On the same day, the Italian submarine Alpino Bagnolini torpedoed and sank the British light cruiser Calypso to the south of Crete.

On 13 June, the Marine Nationale launched 'Vado'. Vice-amiral Emile Duplat’s 3ème Escadre of the Flotte de la Mediterranée comprised the heavy cruisers Algérie, Colbert, Dupleix and Foch, and the destroyers Aigle, Albatros, Vauban, Vautour, Guépard, Lion, Valmy, Verdun, Tartu, Chevalier Paul and Cassard, and on this day departed Toulon and steamed toward Italy. At 04.26 on 14 June, the French heavy cruisers opened fire on shore targets. Firing at a range of 16,400 yards (15000 m), Algérie struck oil storage tanks in Vado Ligure, but soon found subsequent shooting difficult through the smoke pouring from the burning tanks, while Foch fired on a steel mill in Savona. Colbert and Dupleix, firing at a range of 14,215 yards (13000 m), attacked a gas works at Sestri Ponente. In reply, the Italian shore batteries to the west of Genoa and at Savona and at least one armoured train engaged the French ships. A 5.91-in (150-mm) shell from the Batteria Mameli at Pegli penetrated the boiler room of the destroyer Albatros, killing 12 sailors. The crew of the Italian torpedo boat Calatafimi, which was in the Genoa areas as it escorted a minelayer, were taken by surprise by the French attack, but as a result of the prevailing misty conditions, the boat’s commanding officer believed that he would be able to launch a torpedo attack on the French warship. As Calatafimi moved into position, she was sighted and engaged by French destroyers: a near miss damaged the Italian boat’s hull, but she nonetheless managed to launch four torpedoes at the French force, though none of these found a target. A third attempt, aiming for the cruisers Colbert and Dupleix, failed and the boat withdrew toward Genoa. Under pressure from the Italian coastal artillery, Colbert and Dupleix also pulled back. As the cruisers retreated out of the range of the Italian guns, their escorting destroyers opened fire and silenced a shore battery at Cape Vardo.

In the area to the south-east of Savona, motor torpedo boats of the 13a Flottiglia MAS had been on patrol and moved rapidly toward the French force, near Genoa and Savona, once the French ships had opened fire. MAS-539 was able to get within 1,970 yards (1800 m) of Algérie and Foch before firing its torpedoes, although without success. As the French withdrew, MAS-534 and MAS-538 each launched two torpedoes at the French cruisers, but all of these missed. MAS-535 was struck during the motor torpedo boats' attack, resulting in light damage to the boat and three casualties among the crew. The whole French force withdrew as planned and arrived back in port before 12.00 on 14 June. The French ships fired 1,500 rounds in all, and the Italian shore guns about 300.

In co-ordination with the Marine Nationale’s attack, eight Lioré et Olivier LeO 45 bombers of the Armée de l’Air attacked Italian airfields, and nine Fairey Swordfish bombers of No. 767 Squadron of the Fleet Air Arm, based at Hyères, attacked Genoa. The French naval effort prompted Mussolini to order the Italian air force to start attacks on targets in metropolitan France, although reconnaissance operations had already been undertaken.

On 17 June, the French sloop Curieuse forced the Italian submarine Provana to the surface off Oran, and then rammed and sank it, herself sustaining major damage in the process. Provana was the only Italian submarine to be sunk by the Marine Nationale. Further sorties by French cruisers and destroyers on 18 and 19 June resulted in no action. On 21 June, the elderly French battleship Lorraine, supported by the British light cruisers Orion and Neptune, the Australian light cruiser Sydney and four British destroyers, undertook a shore bombardment of the port of Bardia in Libya. French naval aircraft also attacked Livorno on the Italian mainland among some of the last French actions against the Italians.

On 18 June, the staff of the Regia Marina conducted a study which showed that a landing on Malta was not feasible, despite the island’s indifferent defences. This opinion was accepted by Badoglio on 25 June in the course of the first meeting of the Italian chiefs-of-staff during the war.

On 19 June Roatta wrote to the Gruppo Armate Ovest that while there were probably French troops in the fortifications of the 'Ligne Alpine', it was possible that any mobile troops farther to the rear were already retreating. Wholly erroneous and based on wishful thinking rather than factual evidence, this opinion did not permeate down to the front-line commanders, but a general belief in low French morale did, and some Italian officers jokingly lectured their troops on how to behave with French women. When the main offensive began, therefore, the Italian troops, led by overconfident officers, advanced in orderly columns into the range of the French forts. On the same day Mussolini ordered his generals to seek contact with the French, and at 20.50 Roatta issued a directive to 'undertake small offensive operations immediately [and to] make contact with the enemy everywhere, and to harass the enemy forces as harshly as possible'. The main offensive was to begin 'as soon as possible [and] no later than 23 June'. During the morning of 20 June, Mussolini ordered Badoglio to start the offensive by the morning of the following day, adding that 'I do not want to suffer the shame of the Germans occupying Nice and remitting it to us.' Badoglio then passed the order to Graziani with the words 'Tomorrow, the 21^st, at the start of action at 03.00, the 1a Armata and 4a Armata will wholeheartedly attack along the entire front. Goal: a penetration as deep as possible into French territory.' At 17.45 hours Graziani told the Gruppo Armate Ovest: 'The Germans have occupied Lyon, and it must be categorically avoided that they arrive first at the sea. By 3 o’clock tonight, you must attack along the whole front from the Little Saint Bernard to the sea. The air force will contribute through mass bombing of fortifications and cities. The Germans, in the course of tomorrow and the day after it, will send armoured columns from Lyon toward Chambéry, St Pierre de Chartreuse and Grenoble.'

Graziani then modified his directive of 16 June to make the primary Italian objective the great city of Marseille. This final version of the offensive plan had only two main components in the form of Operazione 'M' through the Little Saint Bernard Pass and Operazione 'R' along the Riviera, the proposed third primary axis in the Maddalena Pass being reduced to a diversion. The immediate objective of Operazione 'M' was Albertville, while that of Operazione 'R' was Menton. Then, at 20.00 hours on 20 June, Mussolini countermanded the attack order, but before it was passed to the front-line commands Mussolini received confirmation that German forces were continuing their advance down the Rhône river valley despite the imminent likelihood of an armistice. Mussolini then reversed countermanding order, only shifting the emphasis to the northern sector of the front, as his generals had constantly recommended.

On 20 June, the guns of the Fortezza Chaberton switched targets to the Ouvrage Janus, which could not train its battery of six guns on the Italian position and return fire. With the supporting fire of the fort, the Italian troops were able to advance and capture the village of Montgenèvre. However, no further gains were made in the Briançon sector as the French were able to hold their line. by 21 June, the French had been able to manoeuvre a battery of 280-mm (11-in) mortars of the 154e Régiment d’Artillerie into a position at the foot of the Ouvrage de l’Infernet to engage the Fortezza Chaberton. Over a three-day period, with firing delayed and interrupted by adverse weather, the French were able to silence six of the eight armoured turrets of the Italian fort with a mere 57 large-calibre mortar bombs. Obscured by fog, the two remaining Italian turrets turrets continued to fire until the armistice.

It was on 21 June that the main Italian offensive started when, early that morning, Italian troops crossed the French frontier at points all along the front. Initially, the Italian offensive enjoyed some success. The French defensive line had been weakened by the French high command’s decision to relocate some of the forces in the 'Ligne Alpine' to the north to fight the Germans. The Italian forces attacking through the riviera, totalling some 80,000 men including reserves, advanced about 5 mi (8 km) on 21 June. It was in this sector near the coast that the French had located their strongest concentration of forces, totalling about 38,000 men.

The main Italian attack was that of Guzzoni’s 4a Armata. Generale di Divisione Luigi Neri’s Corpo d’Armata 'Alpino', based on one Alpine division, one Alpini regiment and three Alpini battalions, and reinforced by the corps artillery of Generale di Corpo d’Armata Camillo Mercalli’s IV Corpo d’Armata on its left flank, launched its offensive on a front of 22 to 25 miles (35 and 40 km) between the Col de la Seigne and the Col du Mont. the corps' main axis would have been directed through the Little Saint Bernard Pass, which would have offered the easiest route, had the French not destroyed the bridges. This route was covered by the Redoute Ruinée (the ruins of an old fort), which the French garrisoned with 70 men well equipped with machine guns, and by the avant-poste at Séloges. The total French strength in the defensive arrangement of Bourg St Maurice, which was a part of the sous-secteur (sub-sector) of Tarentaise, was 3,000 or according to some sources 5,500 men with 350 machine guns and 150 other guns, and this strength was backed by another 18 battalions with 60 pieces of artillery. The primary objectives of the Corpo d’Armata 'Alpino' were the capture of Bourg St Maurice, Les Chapieux, Séez and Tignes, and after achieving this the corps was to advance to Beaufort and Albertville.

On 21 June, the right-hand column of the Corpo d’Armata 'Alpino' took the Seigne Pass and advanced several kilometres across a glacier, but were met with heavy fire from Séloges. The Italians quickly outflanked Séloges, and on 24 June charged up the Cormet de Roselend, but were still in the process of completing their encirclement when the armistice was signed. The central column passed through the Little Saint Bernard Pass before being checked by fire from the Redoute Ruinée. Generale di Divisione Vito Ferroni’s 101a Divisione motorizzata 'Trieste' of the Armata di Po was brought up from Piacenza to reinforce the attack, and at 11.00 the fresh division’s motorcycle battalion broke through the pass and began a rapid 1.25-mile (2-km) advance before fording a river under heavy machine gun fire even as Italian engineers repaired the demolished bridge, suffering heavy losses in the process.

On 22 June, the tank battalion of the 101a Divisione motorizzata passed the motorcycle battalion, but was then halted by a minefield. Two L3/35 tankettes became trapped in barbed wire entanglements, and of those following one struck a landmine as it tried to go around the leading pair, another fell into a ditch attempting the same, and the remaining two suffered engine failure. On the same day, a battalion of the 65o Reggimento motorizzato of the 101a Divisione motorizzata was met by French infantry and field fortifications while trying to attack the Redoute Ruinée from the rear. A machine gun unit relieved the motorised troops, who thus abandoned the assault, continuing instead to Séez.

The left-hand column of the Corpo d’Armata Alpino met only weak resistance and reached the right bank of the Isère river on 22 June. By the time of the armistice the central column had occupied Séez, but the Italians never brought up the artillery required to effect the reduction of the Redoute Ruinée, which had meanwhile been reinforced. Although the Italians did manage to damage the fort, its guns continued to hamper passage of the Little Saint Bernard Pass until the armistice. The Corpo d’Armata Alpino thus failed to take its ultimate objective, Bourg St Maurice, and at the armistice allowed the Redoute Ruinée’s garrison march out with the honours of war.

To the south of the Corpo d’Armata Alpino, Generale di Corpo d’Armata Carlo Vecchiarelli’s I Corpo d’Armata of three infantry divisions was to advance along a 25-mile (40-km) front between Mont Cenis and the Col d'Étache. The corps' secondary task was to break through the French forts at Bessans, Lanslebourg and Sollières-Sardières and the defeat of ouvrages (St Gobain, St Antoine and Sapey) overlooking Modane and then to turn north in the direction of Albertville. For these tasks the Battaglione 'Val Cenischia' and Battaglione 'Susa', under Maggiore Costantino Boccalatte of the 3o Reggimento alpino of Generale di Divisione Paulo Micheletti’s 1a Divisione alpina 'Taurinense' were attached to General di Divisione Antonio Scuero’s 59a Divisione montagna 'Cagliari'. The I Corpo d’Armata's main attack was to take the form of a triple-axis drive by the 59a Divisione, involving the capture of Bessans and Bramans, followed by a concerted advance along the Arc river toward Modane. The central column comprised the 1/64o Reggimento and 2/64o Reggimento and the 3/62o Reggimento, which were to advance through the Col des Lacs Giaset and then down the valley of the Ambin river. The 2/63o Reggimento was to cross the Little Mont Cenis Pass and move toward the village of Le Planay, where it was to join the central column, while the 1/63o Reggimento crossed the Pas de Bellecombe and augmented the central column at the village of La Villette. The Battaglione 'Val Cenischia' constituted the left-hand column, which was to pass through the Col d'Étache. It was intended that this battalion synchronise its attack on the flank of Modane with the arrival of the central column. The Battaglione 'Susa' under the command of Maggiore Boccalatte constituted the right-hand column and was to cross the Pas du Chapeau and the Novalesa Pass before following the Ribon river toward Bessans and then the Arc river to Lanslebourg, where it was to link with Colonnello Cobianchi’s 3/64o Reggimento of the 59a Divisione montagna advancing across the Col de Mont Cenis. The Italian reserve comprised Generale di Divisione Arnaldo Forgiero’s 11a Divisione 'Brennero'.

The French garrisons tasked with checking these Italian forces totalled 4,500 men backed by two divisions with 60 tanks behind them. The French also had an advanced post of three blockhouses at Arcellins, but these were fog-bound for much of the time.

The Italian central column began its descent through the Col des Lacs Giaset shortly after 12.00 on 21 June, and began to meet strong resistance as it approached the Ambin river. The 2/63o Reggimento coming down from the Little Mont Cenis Pass overcame weak resistance and then linked with the central column. Some small groups were detached to remain behind and mop-up any surviving French resistance, while the bulk of the column continued toward Bramans. All the battalions of the 59a Divisione montagna assembled round a chapel outside Bramans, and, after destroying the French field fortifications with artillery fire, had taken the town by the end of the offensive’s first day. One battalion was diverted to Termignon to link with the Battaglione 'Susa' while the rest proceeded toward Modane. The Battaglione 'Val Cenischia' met no resistance as it crossed the Col d'Étache and Col de Bramanette, and emerged in the rear of the Fort de la Balme. The fortifications were taken on 23 June by the 50a Divisione montagna, but the forts in front of Modane and St Gobain at Villarodin and the Barrière de l’Esseillon, were tougher nuts top crack. The Italians attempted to flank these French fortifications from the south, and their artillery engaged the forts' guns, but none of these forts had been reduced by the time the armistice came into effect, although the advance units of the 59a Divisione montagna were with 3.25 miles (5 km) of Modane.

While the Battaglione 'Susa' occupied Lanslebourg and moved on Termignon, the 3/64o Reggimento had been delayed. Its route was heavily mined and strewn with anti-infantry and anti-tank obstacles. One battalion of the 231o Reggimento 'Avellino' and one tank battalion of the 11a Divisione were therefore sent to its aid. Two L3/35 tankettes hit landmines on the narrow cliffside road, halting the entire column and allowing the French artillery to destroy the armour tapped and immobile behind the two leading vehicles. The Italian infantry could advance only very slowly in the face of heavy fire and, in some cases, passed well-concealed French machine gun nests and then started to take fire from their rear. The Italians managed to surround the powerful Fort de la Turra, but at the time of the armistice this and the advanced post at Arcellins were still offering resistance. The Italian column had not reached Lanslebourg, which had been occupied days earlier by Boccalatte’s force.

Pintor’s 1a Armata had been spared responsibility for the main attack, which therefore fell to the 4a Armata farther to the north, as a result of appeals by its commander on 20 June. The southern part of the 1a Armata, between Monte Grammondo to the coast, was held by Generale di Divisione Alessandro Gloria’s 37a Divisione montagna 'Modena' and Generale di Divisione Alberto Vasarri’s 5a Divisione fanteria 'Cosseria', with the 52a Divisione motorizzata 'Torino' of the Armata di Po in reserve. The 1^st Army started its offensive along the whole front on 20 June and in most places was easily repulsed by the French artillery.

On 21 June, the units advancing through the Val Roia successfully occupied Fontan. The 5a Divisione, advancing along the coast toward Nice, was to have been met by a number of Alpini progressing down the valley of the Vésubie river and also by the marine infantry of the Reggimento 'San Marco' delivering an amphibious landing behind the Ouvrage Cap Martin. The amphibious assault had to be cancelled for an assortment of logistical reasons including engine failures, overloaded boats and rough sea. Lacking sufficient landing craft, the Regia Marina had commandeered fishing boats and even a number of pleasure boats. The Italian navy did attempt some landings, but after several craft had grounded the whole undertaking was terminated. The 5a Divisione was met by a barrage of shellfire from Cap Martin and the Ouvrage Mont Agel, which destroyed an armoured train. Even so, with the aid of thunderstorms and fog, the division occupied the lower quarter of St Paul de Vence and La Grange on 22 June. Mussolini then gave the order that the division was to advance regardless of losses.

On the night of 22/23 June, still covered by fog, the 5a Divisione bypassed Cap Martin and entered the Garavan quarter of Menton. The bypassed French troops nonetheless continued to fight, firing the fort’s artillery at Italian coastal shipping, until the signature of the armistice. The fighting in the streets of Menton was fierce. The Italians pushed through the Baousset quarter and took the hilltop Capuchin monastery of Notre Dame de l’Annonciade on 23 June. A planned naval landing at Garavan by a Milizia Volontaria per la Sicurezza Nazionale ('blackshirt') unit on 24 June had to be cancelled as a result of high waves and the tactically inhibiting presence of a full moon. With the exception of the garrison of the advanced fort of Pont St Louis, the French slowly fell back from Menton.

On 24 June, the Italian infantry reached the plain of Carnolès and were repulsed by the French artillery, and Italian warplanes then bombed the French barracks there. On the same day the fort of Pont St Louis engaged in its last artillery duel with the Italians. No vehicles managed to cross the bridge before the armistice. The capture of Menton, the 'the pearl of France' was an undeniable if costly success for the Italians. Mussolini arrived to view the scene of the battle on 1 July, and later claimed, in a radio broadcast from Rome, that the Italian 'infantry were supported by an artillery train which came through the tunnel under La Mortola and shelled the strongly held [Menton] in which the [French] were maintaining an obstinate resistance'.

Along the 1a Armata's northern front, General di Divisione Francesco Sartoris’s 33a Divisione montagna 'Acqui', based at the entrance of the Valle Stura di Demonte, comprised six battalions and one legion of the MVSN, and possessed 30 81-mm (3.19-in) mortars, 24 75-mm (2.95-in) Obice da 75/18 2.95-in M34 mountain howitzers and 12 Obice da 100/17 modello 16 100-mm (3.94-in) howitzers. It also had 3,500 mules (for the pack carriage of its artillery) and horses, 68 motor vehicles, 71 motorcycles and 153 bicycles. The initial deployment of the division was defensive, but on 20 June the division’s orders were to advance 37 miles (60 km) up the valley into French territory on the valley’s only road. The division’s radio equipment failed in the rainy conditions, and the formation soon left its food and other supplies far to the rear, but on 23 June it reached the Maddalena Pass, now with only one Obice da 100/17 howitzer in tow, and began descending the Ubaye river valley into France. Heavy snow and fog slowed the division’s advance, but also prevented the French gunners from adjusting their aim, and the division did not reach the French fortification until a time late on 24 June, by which time the armistice had been signed. The 33a Divisione montagna had lost 32 men dead and 90 wounded, together with 198 men incapacitated by frostbite and 15 missing. Because of a lack of artillery in the Ubaye river valley, the division had not fired on the French forts.

On 17 June, the day after he transmitted a formal request for an armistice to the German government, Paul Baudoin, the French foreign minister, handed Valerio Valeri, the papal nuncio, a note stating that 'The French government, headed by Maréchal Pétain, requests that the Holy See transmit to the Italian government as quickly as possible the note it has also transmitted through the Spanish ambassador to the German government. It also requests that he convey to the Italian government its desire to find together the basis of a lasting peace between the two countries.' During the morning of the same day, Mussolini received word from Hitler that France had asked Germany for an armistice, and he went to meet Hitler at Munich, charging Roatta, Ammiraglio di Squadra Raffaele de Courten and Generale di Brigata Aerea Egisto Perino to co-ordinate the drafting of Italy’s demands. The final list of demands presented to the French was mild, however, for by this time Italy had dropped its claims to the Rhône river valley, Corsica, Tunisia and French Somaliland.

On the evening of 21 June, Dino Alfieri, the Italian ambassador in Berlin, transmitted to Rome the text of the armistice terms which Germany was imposing on France. According to Ciano, 'under these conditions, Mussolini is not prepared to make territorial demands…and [will] wait for the peace conference to make all our formal demands'. He added that Mussolini wished to delay the meeting with the French in the hopes that Gambara’s force would be able to take Nice.

At 15.00 hours on 23 June, the French delegation, headed by Général d’Armée Charles Léon Clément Huntziger, commander of the 4ème Groupe d’Armées and the officer who had signed the armistice with Germany on the previous day, landed in Rome as part of a party delivered by three German aircraft. The French negotiators were the same as those who had treated with the Germans. The first meeting of the two delegations took place at 19.30 at the Villa Incisa all’Olgiata on the Via Cassia and lasted a mere 25 minutes, during which Roatta read out Italy’s proposed terms. Huntziger requested a recess to confer with his government and Ciano adjourned the meeting until the following day. During the adjournment, Hitler informed Mussolini that he thought the Italian demands too little, and proposed linking the German and Italian occupation zones, but Roatta convinced Mussolini that it was too late to change Italy’s demands.

At 19.15 hours on 24 June, at the Villa Incisa, after receiving his government’s authorisation, Huntziger and Badoglio signed the armistice on behalf of the French and Italians respectively. Both the German and Italian armistices came into effect at 00.35 on 25 June. Just minutes before the signatures were appended to the agreement, Huntziger had asked Badoglio to remove the clause calling for the repatriation to Italy of political refugees: Badoglio consulted Mussolini, who agreed.

The Franco-Italian armistice established a modest demilitarised zone 31.25 miles (50 km) deep on the French side of the border, thus eliminating the threat of the 'Ligne Alpine', but was in fact no more than the area which the Italians had occupied by the time of the armistice. The Italians therefore occupied an area of 321.25 sq miles (832 km²) with a population of 28,500 persons including the 21,700 residents of Menton. Italy retained the right to interfere in French territory as far as the Rhône river, but did not occupy this area until after the Allied 'Torch' invasion of French North-West Africa in November 1942. Demilitarised zones were also established in France’s African colonies bordering those of Italy, which was given the right to use the port of Djibouti in French Somaliland and the French section of the railway linking Addis Ababa and Djibouti. More importantly, the naval bases of Toulon, Bizerte, Ajaccio and Oran were also to be demilitarised.

The reported army casualties for France vary between 37 and 40 killed, 42 and 62 wounded, and 145 and 155 taken prisoner in the fighting with Italy, and the Armée des Alpes also lost 20 men killed, 84 wounded and 154 taken prisoner in the fighting with the German forces advancing from Lyon. The Italian casualties amounted to 631 or 642 men killed, 2,631 wounded, 616 missing and 2,151 men afflicted by frostbite. The official Italian record had been compiled by 18 July 1940, and as a result many of the fallen still lay hidden under the snow of higher terrain, and it is probable that most of those whom the Italians listed as missing were in fact dead. The official number of French prisoners of war was 155, and all Italian prisoners of war (perhaps as many as 1,141 though no official tally was taken) were released immediately. The French prisoners were despatched to the camp at Fonte d’Amore near Sulmona, where they were later joined by 200 British and 600 Greek prisoners. The prisoners were treated in accordance with the laws of war by the Italians, but probably fell into German hands after Italy’s surrender of September 1943.