Operation Weiss (i)


'Weiss' (i) was the German invasion and conquest of Poland (1 September/6 October 1939).

The undertaking was of strategic significance in its own right, triggered World War II, and revealed that Germany was a major military power with skilled commanders and significant armed forces based on fast-moving mobile elements with very effective air support.

The invasion of Poland was carried out by Germany from the north, west and south, together with a small force from the German puppet state of Slovakia, and by larger forces of the USSR from the east. The invasion prompted Poland’s western allies, France and the UK, to declare war on Germany on 3 September, and the British lead was quickly followed by declarations of war by Canada, Australia and New Zealand among others.

The campaign began on 1 September, one week after the signature of the Molotov-Ribbentrop Pact, a non-aggression agreement between Germany and the USSR incorporating a secret protocol for the USSR’s concomitant seizure of eastern Poland, and ended on 6 October, when Germany and the USSR had complete control of Poland.

The German pretext for the invasion was the so-called 'Gleiwitz incident', a staged attack on 31 August against the German radio station Sender Gleiwitz in the town of Gleiwitz in the German region of Upper Silesia bordering western Poland. Small in size but large in implication, this operation was one of several parts of 'Himmler', a German plan designed to create the appearance of Polish aggression against Germany, and thus 'justify' Germany’s carefully conceived aggression against Poland. On the day following the Gleiwitz attack, Germany launched 'Weiss' (i), and in a speech in the Reichstag Adolf Hitler cited 21 border incidents, including three categorised as 'very serious', as justification for Germany’s 'defensive action' against Poland.

In January 1933 the Nazi party had come to power in Germany under the leadership of Hitler, and as early as the autumn of 1933 the new German leader had started to envisage practical matters designed to bring about the annexation by Germany of countries and territories such as Austria, the Bohemian and Moravian parts of Czechoslovakia and the western part of Poland, and also the creation of satellite (or client) states politically and economically subordinate to Germany. As part of this long-term policy, Hitler at first pursued a policy of rapprochement with Poland in an effort to improve German/Polish relations, and this culminated in the German-Polish Non-Aggression Pact of 26 January 1934. Hitler’s foreign policy had earlier worked to weaken the ties between Poland and France, and now attempted to manoeuvre Poland into the Anti-Comintern Pact of 25 November 1936 designed to create a co-operative front against the USSR. Had this ploy proved successful, Poland would have been allocated territory to its south-east and north-east in Ukraine and Belorussia in the event that it agreed to wage war against the USSR, but the concessions the Poles were concomitantly expected to make would have meant that Poland would have become largely dependent on Germany, functioning as little more than a client state. The Poles rightly feared that their independence would eventually be threatened.

To provoke war with Poland in order to gain Lebensraum, the 'living room' which the Nazis desired as the additional and largely agricultural territories into which it could settle ethnic Germans, the Nazis used as a pretext a claim to the Free City of Danzig and the Polish 'corridor' to the Baltic Sea, which separated the German exclave of East Prussia from the rest of the Germany. A narrow area long disputed by Poland and Germany, and inhabited by a Polish majority, the so-called Polish 'corridor' had been allocated to Poland by the Treaty of Versailles of 1919, which had formally ended Germany’s involvement in World War I on decidedly anti-German terms. Many Germans also desired the reincorporation of the city of Danzig and its environs, together constituting the Free City of Danzig, into Germany. Danzig was a port city with a German ethnic majority, but had been separated from Germany by the Treaty of Versailles and made the nominally independent Free City of Danzig. Hitler sought to exploit this as a reason for war, thereby reversing these territorial losses, and on many occasions he appealed directly to German nationalism by promising to 'liberate' the German minority still living under Polish rule in the 'corridor', as well as Danzig.

The invasion was known in Germany as the 1939 Defensive War as Hitler proclaimed, as detailed below, that Poland had attacked Germany and that the 'Germans in Poland are persecuted with a bloody terror and are driven from their homes. The series of border violations, which are unbearable to a great power, prove that the Poles no longer are willing to respect the German frontier.'

Poland had participated in the partition of Czechoslovakia which followed the Munich Agreement of 29 September 1938, although it was not actually involved in the agreement. Poland coerced the now impotent Czechoslovakia to surrender the region of Českż Těsķn by the despatch of an ultimatum to that effect on 30 September, and this ultimatum was accepted by Czechoslovakia on the following day. This small region had a Polish majority and its possession had been disputed between Czechoslovakia and Poland in the aftermath of World War I. More important were the minor Polish gains at the expense of Slovak territory, in the form of several villages in the regions of Čadca, Orava and Spis, as these later served as the justification for Slovak state to join the German 'Weiss' (i) invasion.

By 1937, Germany had started to increase its demands for Danzig, while at the same time proposing the construction of an 'extraterritorial' road through the Polish 'corridor' to provide a direct link between East Prussia and Germany proper. Poland rejected this proposal, for it feared that any acceptance of of these demands would pave the way to an increasing Polish subordination to the will of Germany and thus an eventual loss of independence, as in fact happened to the Czechoslovaks. The Polish leadership also had a very real distrust of Hitler’s veracity and honour. Moreover, Germany’s collaboration with the anti-Polish Ukrainian nationalists of the Organisation of Ukrainian Nationalists, which was seen as an effort to isolate and weaken Poland, further weakened Hitler’s credibility in Polish minds. The British were also well aware of the situation between Germany and Poland, and on 31 March 1939 Poland formed a military alliance with the UK and France, ensuring that Polish independence and territorial integrity would be defended with British and French support should Poland be threatened by Germany. However, Neville Chamberlain and Lord Halifax, the British prime minister and foreign secretary respectively, still hoped to be able to reach a compromise with Hitler with regard to Danzig, and possibly the Polish 'corridor'. What what now appears to have been extraordinary naivety, Chamberlain and his supporters believed war could be avoided and hoped Germany would agree to leave the rest of Poland alone.

German hegemony over central Europe was also at stake, and in May 1939 Hitler revealed to his close party associates that, as far as he was concerned, the real issue was not Danzig but rather the pursuit and winning of Lebensraum for the German people.

With tensions mounting, Germany also turned to aggressive diplomacy. On 28 April 1939 Germany unilaterally withdrew from both the German-Polish Non-Aggression Pact of 1934 and the Anglo-German Naval Agreement of 18 June 1935. Discussions about Danzig and the 'corridor' broke down and months passed without any diplomatic interaction between Germany and Poland. During this time Germany learned that France and the UK had failed to secure an anti-German alliance with the USSR, and that the latter was interested in seeking an anti-Polish alliance with Germany. Hitler had already issued orders to prepare a possible 'solution of the Polish problem by military means', in short the 'Weiss' (i) scenario.

In May 1939, in a statement to his senior military leadership even as it was planning the invasion of Poland, Hitler made it clear that the invasion would not come without resistance, as it had when the rump of Czechoslovakia was absorbed by Germany in March 1939.

However, with the surprise signing of the Molotov-Ribbentrop Pact on 23 August, resulting from secret negotiations in Moscow, Germany removed the possibility of Soviet opposition to a campaign against Poland and war became imminent. In fact, the Soviets agreed not to aid France or the UK in the event of their going to war with Germany over Poland and, in a secret protocol, the Germans and Soviets agreed to divide Eastern Europe, including Poland, into two spheres of influence: the western one-third of the country, as well as Lithuania and a strip of Polish territory bordering southern Lithuania, was to go to Germany and the eastern two-thirds, as well as the Bessarabian part of Romania, Latvia, Estonia and Finland, were to go to the USSR. These arrangements were later significantly changed.

The start of the German invasion was originally scheduled for 04.25 on 26 August. However, on 25 August, the Polish-British Common Defence Pact was signed as an annex to the Franco-Polish Military Alliance, and in this accord the UK committed itself to the defence of Poland, guaranteeing to preserve Polish independence. At the same time, the British and the Poles were hinting to Berlin that they were willing to resume discussions. This was not how Hitler hoped to frame the imminent conflict, so he wavered and postponed his attack until 1 September, managing effectively to halt 'Weiss' (i) on the very eve of its scheduled start.

There was one exception, however, for during the night of 25/26 August, a German sabotage group which had not learned of the postponement made an attack on the Jabłonków pass and Mosty railway station in Polish Silesia within the context of 'Himmler'. Part of the German plan for the invasion of Poland was the use of several small groups of Germans dressed in inconspicuous but rugged casual clothing to cross the German/Polish border during the night preceding the invasion in order to seize key strategic points before dawn. The element of the secret Abwehr (military intelligence) battalion detailed to undertake these operations was given the cover designation Bau-Lehr-Kompanie zbV 800 (800th Construction Training Company for Special Duties), and a group under the command of Leutnant Dr Hans-Albrecht Herzner of the Abwehrstelle Breslau was ordered to prepare the way for the assault of the 7th Division by infiltrating across the border and taking the railway station at Mosty in the Jabłonków pass in the Carpathian mountains and thereby prevent the destruction of the single-track railway tunnel which was the shortest connection between Warsaw and Vienna.

The Jabłonków pass separates the Moravian-Silesian Beskid and Silesian Beskid mountain ranges, and is one of the most important transport routes in the western part of the Carpathian mountains. Together with the territory of Zaolzie, it had been annexed by Poland in October 1938, and thus Poland gained control of a key railway connection. The Germans knew that failure to capture the railway line and the tunnel would seriously affect German movements in southern Poland.

The task of Herzner’s detachment was to capture both the rail station at Mosty and the strategic tunnel to prevent its destruction by Polish forces, and was ordered to occupy the Jabłonków pass before the outbreak of hostilities. The Germans were ordered to disable possible Polish demolition systems and open the way for the 7th Division from Munich. The unit comprised mostly volunteers, members of the German minority of Zaolzie, some of whom belonged to the Kampf-Organisation in Jabłonków.

The Polish army headquarters was fully aware of the strategic importance of the tunnel, which was readied for demolition as early as June 1939 by men of the 21st Engineer Battalion from Bielsko-Biała, under the command of Pułkownik Witold Pirszel, a mining engineer in civilian life. The tunnel was guarded by men of the local border guard post from the village of Świerczynowiec, and an infantry platoon of the 4th Regiment of Podhale Rifles. During the summer of 1939, after the passage of the last train on every day, Polish sappers armed the explosives for the night on both sides of the 330-yard (300-m) tunnel.

The German detachment of some 70 or, according to other sources, 24 agents dressed in civilian clothes left Čadca late in the evening of 25 August, and during the night crossed the Polish/Slovak border near the mountain of Velkż Polom and reached the station at Mosty at around 04.00 on 26 August, wholly unaware that Hitler had ordered the postponement of 'Weiss' (i) to 1 September. The Germans set up positions on a hill near Mosty station and began shooting at the station building, as well as at a house in which the headmaster of a local Polish school lived. In the following minutes, the Germans captured the station after some fighting, and took prisoner a group of workers on their way to the Třinec iron and steel factory. There is evidence that Herzner persuaded a Polish lieutenant at Mosty station to order the Polish soldiers to stop fighting as Germany had been at war with Poland since 04.24, and the bloodshed was unnecessary. The Germans were unaware, however, that the station was equipped with a military communication system in its basement, and from here a telephonist managed to call Polish units guarding the tunnel, and the alarm was raised. Polish sentries armed with machine guns took positions at both ends of the tunnel and an observation post was established. A chaotic exchange of fire took place, and after this the Germans realised that the operation had failed and scattered in the nearby woods. Some attackers managed to capture a locomotive and tried to enter the tunnel, but were repelled by Polish police. The Germans remained under heavy fire as they tried to withdraw to Slovakia. They finally managed to pull back at about 12.00 on 26 August, with two of their men wounded.

After the incident, Generalmajor Eugen Ott, commander of the 7th Division that was concentrating in the area, apologised to Generał brygady Józef Kustroń, commander of the 21st Mountain Division stationed nearby and responsible for border protection. Ott claimed that the action had been staged by an 'insane' individual acting on his own. The Jabłonków tunnel was finally blown by Pirszel at 06.00 on 1 September a few minutes before German troops arrived. Rail communication was partially reintroduced in February 1940, and in total in 1941.

On 26 August, Hitler tried to dissuade the British and the French from interfering in the forthcoming conflict, even pledging that German forces would be made available to the British empire in the future. The negotiations convinced Hitler that there was little chance the western powers would declare war on Germany and, even if they did, the lack of territorial guarantees to Poland would make them willing to negotiate a compromise favourable to Germany after its conquest of Poland. Meanwhile, the increased number of overflights by high-altitude reconnaissance aircraft and cross-border troop movements suggested strongly that war was imminent.

On 29 August, prompted by the British, Germany made one last diplomatic offer, with 'Weiss' (i) yet to be rescheduled. During the evening, the German government responded in a communication that it aimed not only for the restoration of Danzig but also of the Polish 'corridor', which had not previously been an element of Hitler’s demands, in addition to the safeguarding of the German minority in Poland. The communication indicated that Germany was willing to start negotiations, but indicated that a Polish representative with the power to sign an agreement had to arrive in Berlin no later than the following day, and that it the meantime it would draw up a set of proposals. The British cabinet was pleased that negotiations had been offered but, remembering how Emil Hįcha had been forced to sign away Czechoslovakia under similar circumstances only a few months earlier, regarded the requirement for an immediate arrival of a Polish representative with full signing powers as an unacceptable ultimatum. During the night of 30/31 August, Ribbentrop read a 16-point German proposal to the British ambassador. When the ambassador requested a copy of the proposals for transmission to the Polish government, Ribbentrop refused on the grounds that the requested Polish representative had failed to arrive by 24.00. When Ambassador Józef Lipski went to see Ribbentrop later on 31 August to indicate that Poland was favourably disposed to negotiations, he announced that he lacked the full power to sign, and Ribbentrop dismissed him. It was then broadcast that Poland had rejected Germany’s offer, and negotiations with Poland came to an end. Hitler issued orders for the start of the invasion soon after this with the issue of the Führerweisung Nr 1.

On 30 August the Polish navy sent its destroyer flotilla to the UK in 'Peking'. On the same day, Marszałek Polski Edward Śmigły-Rydz (Rydz-Śmigły up to the time of his elevation to marshal in 1936) announced the mobilisation of the Polish forces, but later in the same day revoked the order as a result of pressure by the French, who apparently still hoped for a diplomatic settlement despite the fact that the Germans were fully mobilised and concentrated on their start lines along the German/Polish border. During the night of 31 August/1 September, the Gleiwitz incident, a false flag attack on the radio station, was staged near the border city of Gleiwitz in Upper Silesia by German units posing as Polish troops, as part of the broader 'Himmler' undertaking. On 31 August, Hitler ordered hostilities against Poland to start at 04.45 on the following morning. Because of the earlier revocation of its mobilisation order, Poland managed to mobilise only 70% of its planned forces, and many units were still forming or moving to their designated front-line positions.

The German armed forces had a substantial quantitative advantage over those of Poland, and had also developed a significant qualitative superiority in the period before the outbreak of hostilities. The army had some 2,400 tanks organised into six Panzer divisions, which used elements of the new Blitzkrieg operational doctrine which mandated that these divisions should act in co-ordination with the other elements of the military, driving holes in the opponent’s line and isolating selected units for encirclement and subsequent destruction by the following less mobile motorised and foot infantry with their horse-drawn artillery. The Blitzkrieg concept was not used fully in 'Weiss' (i), for there was still some resistance to this novel concept by some of the army’s more orthodox senior officers, who wanted to use a more traditional approach based on the concept of Vernichtungsgedanken, or an emphasis on envelopment tactics to create pockets in a broad-front campaign of annihilation. German aircraft also played a role at the operational as well as the tactical level in 'Weiss' (i).

The air force provided both operational and tactical air power, and its three most important elements were the fighter arm which provided air superiority and engaged in support of the ground forces, the dive-bomber and close support arm which operated as 'flying artillery' in the provision of tactical support for the ground forces on the battlefield, and the tactical bomber arm which used its medium bombers to destroy the opposing forces' lines of communication and rear areas. German warplanes thus played a major role in the campaign. Bombers also attacked cities, causing major losses among the civilian population through terror bombing and strafing. The Luftwaffe forces comprised 1,180 Messerschmitt Bf 109 single- and Bf 110 twin-engined fighters, 290 Junkers Ju 87 Stuka dive-bombers, 290 twin-engined medium bombers largely of the Dornier Do 17 and Heinkel He 111 types, 550 transport aircraft, 350 reconnaissance aircraft, modest numbers of Henschel Hs 123 close-support fighters and 240 naval aircraft. In total, therefore, Germany had something in the order of 4,000 aircraft, most of them modern, and 2,315 of these were assigned to 'Weiss' (i). As a result of its earlier participation in the Spanish Civil War, the Luftwaffe was probably the most experienced, most highly trained and best-equipped air force in the world in September 1939.

Bombers attacked Polish concentration areas deep behind the front, cut Poland’s major lateral as well as radial arteries of communication, decimated Polish industries, and also undertook a 'terror bombing' programme against Polish cities to destroy Polish morale and also inflict substantial losses on the civil population.

While the Poles could call on some 840 obsolescent aircraft to support their armies, the Germans thus had some 1,930 modern warplanes and a smaller number of older warplanes allocated to General Albert Kesselring’s Luftflotte I in support of Generaloberst Fedor von Bock’s Heeresgruppe 'Nord' and General Alexander Löhr’s Luftflotte IV in support of Generaloberst Gerd von Rundstedt’s Heeresgruppe 'Süd'.

On the ground the Germans had 1.5 million men to the Poles' 950,000 men, but more significantly could call on some 2,750 tanks and 9,000 pieces of artillery to the Poles' 880 much lighter armoured fighting vehicles and 4,300 pieces of artillery.

In the 1936/39 period, Poland had made a heavy investment in the industrialisation of the so-called Central Industrial Region, for it had been appreciated over some years that war with Germany was a shorter- rather than longer-term probability. The overall Polish assumption, in fact mirroring the prognostication which Hitler had given to his senior military commanders and industrialists, was that no such was likely before 1942. To raise further funds for continued industrial development, Poland was in fact selling to export customers much of the modern equipment it produced. Although the Polish army numbered almost 1 million men, fewer than half of these had been fully mobilised by 1 September, and those mobilised after the start of hostilities suffered major losses after the Luftwaffe had started to attack the Polish public transport system. The Polish military had armoured forces notably smaller and less well equipped than those of the Germans, and as these were dispersed in comparatively small units for infantry support rather than grouped into homogeneous formations they could therefore play only a minor part in the war.

The organisation and operational doctrines used by the Poles in September 1939 had been shaped largely by the success of the Polish army in the Polish-Soviet War (1919/21). Unlike the largely static warfare which had characterised World War I on the Western Front and, to a lesser extent, the Eastern Front, the Polish-Soviet War had been a conflict in which the decisive factor had been the mobility of substantial cavalry formations. Poland was conscious of the benefits of mobility but was unwilling, and indeed unable, to invest heavily in many of the expensive and, as it then believed, unproved weapon types which had emerged during the 1920s and first half of the 1930s. However, it should be noted that Polish cavalry brigades were used as a form of mobile mounted infantry, and gained some successes against German infantry and cavalry.

The Polish air force was at severe quantitative and qualitative disadvantages to the Luftwaffe but, contrary to popular belief, was not destroyed on the ground at the outset of the campaign. Although the Polish air force lacked modern fighters, its pilots were highly trained and indeed secured a significant numbers of aerial victories. In overall terms, Poland had only about 400 first-line aircraft, including 169 fighters, and numbers of obsolete transport, reconnaissance and training aircraft.

The Polish navy was small, and comprised only destroyers, submarines and smaller support vessels. As noted above, most of the larger Polish surface units followed the 'Peking' plan and thus left Polish ports on 29 August to escape into the North Sea to join the Royal Navy. Submarines participated in 'Worek', which was an unsuccessful attempt to sink German shipping in the Baltic Sea. In addition, many Polish mercantile vessels reached British ports and became a major asset in the convoy effort undertaken from a time soon after this to keep the UK supplied with food, raw materials, weapons and men, and to deliver military formations and equipment to other theatres.

In overall terms, at the start of 'Weiss' (i) on 1 September Poland could call on some 950,000 men, and its primary combat assets were 39 divisions some of which were never fully mobilised and concentrated, 16 brigades, 4,300 pieces of artillery, 880 tanks and 400 aircraft, whereas the Germans could call on 1.5 million men, and its primary combat assets were 60 divisions, six brigades, 9,000 pieces of artillery, 2,750 tanks and 2,315 aircraft; the Slovak puppet state also contributed slightly more than 51,000 men in three divisions.

'Weiss' (i) had been schemed under the supervision of Halder in his capacity as chief-of-staff of the Oberkommando des Heeres, and directed by Generaloberst Walther von Brauchitsch, the army’s commander-in-chief. 'Weiss' (i) ordained the start of limited hostilities before the declaration of war, which was planned on the basis of a slightly modified version of the traditional doctrine of mass encirclement and the destruction of the enemy’s forces. Germany’s matériel advantages, including modern aircraft and armour, were to be of signal advantage. Though still very far from completely mechanised, but aided by fast-moving artillery and all the relevant ancillary services, the infantry would be supported by the German armour and small numbers of Schützen lorried infantry regiments to aid the speed of the infantry’s advance and bring decisive weight to bear rapidly on key sectors of the Polish front with a view to isolating sizeable Polish formations and then destroying them. The type of far-sighted Blitzkrieg concept currently being advocated by officers such as General Heinz Guderian would have used the armour to effect rapid breakthroughs of the front, through which the armour would then pass to drive deep into the Polish rear areas. But the Polish campaign was effectively fought on what were at the time more orthodox lines.

In good weather conditions and given its large, flat plains, Poland is ideal country for mobile warfare. In 1939 Poland had almost 3,500 miles (5635 km) of border including 1,250 miles (2010 km) contiguous with Germany in the west and north (facing East Prussia). Another 500 miles (800 km) had also been under threat since the time of the Munich agreement, for the German incorporation of Bohemia and Moravia, and creation of the German puppet state of Slovakia, meant that Poland’s south-western border was now also open to invasion.

The German planners intended to make full use of their long border with Poland to launch great breakthrough and enveloping manoeuvres from three directions. In the north was von Bock’s Heeresgruppe 'Nord' 1, divided by Danzig and the Danzig 'corridor' into two portions and possessing, in addition to its forward formations, reserves amounting to Generalleutnant Ferdinand Schaal’s 19th Panzerdivision, Generalleutnant Friedrich von Rabenau’s 73rd Division, Generalleutnant Hugo Höfl’s 206th Division and Generalleutnant Moritz Andreas’s 20th Division.

In the west was von Rundstedt’s Heeresgruppe 'Süd' divided into three major groupings 2, and the army group reserves amounted to General Eugen Ritter von Schobert’s VII Corps (Generalleutnant Friedrich Bergmann’s 27th Division and Generalleutnant Georg Braun’s 68th Division), Generalleutnant Walter Keiner’s 62nd Division, Generalleutnant Rene de l’Homme de Courbičre’s 213th Division, Generalleutnant Johann Pflugbeil’s 221st Division and, in the throes of arriving, Generalleutnant Ludwig Kübler’s 1st Gebirgsdivision.

The 14th Army was supported by the Slovak formations of General II Treidy Ferdinand Čatlos’s Field Army 'Bernolak' (General II Treidy Antonin Pulanich’s 1st Division 'Janosķk', Plukovnik Ivan Imru’s [later General II Treidy Alexander Čunderlik’s] 2nd Division 'Skultéty', General II Treidy Augustķn Malįr’s 20th Division 'Razus', and Plukovnik Ivan Imru’s Fast Troops Group 'Kalinčiak').

Within Poland, the Selbstschutz units of ethnic Germans, prepared secretly before the war, had been instructed to undertake diversionary and sabotage operations.

All three of the German invasion axes were to converge on Warsaw, while the main Polish army formations were to be encircled and destroyed in the area to the west of the Vistula river.

The Polish defence plan was 'Zachód' (west), which was adversely affected by the political rather than military decision to deploy the bulk of the Polish army close to the the German/Polish border in a lengthy cordon defence with virtually no depth and thus no scope for manoeuvre: in overall terms, therefore, the Polish deployment was ideal suited to the German plan for rapid breakthroughs and deep encirclements. The Polish decision resulted from the UK’s promise to come to Warsaw’s military aid, and from the desire of the Polish government to protect the nation’s most valuable natural resources, industry and population centres, which lay near the western border in the region of Silesia. The Polish government’s thinking was centred on the need to provide the maximum possible protection for such regions, especially as many politicians feared that if Poland should retreat from the regions disputed with Germany, France and the UK would reach a separate peace with Germany analogous to the Munich agreement. In addition, neither of these countries had specifically guaranteed Poland’s borders or territorial integrity. Poland therefore disregarded French advice to deploy the bulk of its strength behind the natural barriers provided by the wide Vistula and San rivers, even though some Polish generals supported it as a better strategy. 'Zachód' did make provision for the Polish armies to retreat deeper into the country as and when dictated by events, but this was schemed as a measured retreat to take up prepared positions near rivers such as the Narew, Vistula and San, so giving the country time to complete its mobilisation. The Polish forces 3 were then to go over to a general counter-offensive when the France and the UK started the offensive operations which the Poles believed their allies had promised.

These forward-based formations were backed by limited reserve formations. Generał brygady Tadeusz Piskor’s Lublin Army was an improvised formation created on 4 September with the Warsaw Armoured Motorised Brigade and various smaller units in a concentration round Lublin, Sandomierz and the upper reaches of the Vistula river. Generał dywizji Stefan Dąb-Biernacki’s Prusy Army was created in the summer of 1939 as the main reserve of the commander-in-chief and, according to 'Zachód', was to be composed of units mobilised as the second and third waves. Its primary purpose was to co-operate with the neighbouring Poznań and Kraków Armies. The Prusy Army was mobilised in two groups. Because of the unexpected speed of the German advance, each of these groups entered combat separately and most units did not reach full mobilisation. The Prusy Army had as its primary formations the 39th and 44th Divisions, and two sub-formations in the form of Dąb-Biernacki’s own Northern Group with the 13th, 19th and 29th Divisions, the Wileńska Cavalry Brigade, and the 1st Tank Battalion; and Generał brygady Stanisław Skwarczyński’s Southern Group with the 3rd, 12th and 36th Divisions. Although under the nominal command of Rómmel, the Warsaw Army was actually commanded by Generał brygady Walerian Czuma, and was created on 10 September from an assortment of formations and units in the area of Warsaw and the fortress region of Modlin. At first it comprised some 25 infantry battalions and 40 tanks, but it was later reinforced by forces of the Łódź Army and elements of the Modlin Army. In its definitive form the Warsaw Army had three major sub-formations, in the form of the Modlin Fortress with elements of the 2nd, 8th, 28th and 30th Divisions, the Western Approach with the reinforced 13th and 30th Divisions, elements of the 25th Division and the Combined Cavalry Brigade, and the Eastern Approach with single regiments of the 5th and 8th Divisions, the 20th and 44th Divisions, and the 1st and 2nd 'Defenders of Praga' Regiments. The Operational Group 'Wyszków' was the main reserve of the Polish forces on the northern front, and comprised the 1st, 35th and 41st Divisions.

The Polish army’s most pessimistic fallback plan was based on a withdrawal behind the San river into the south-eastern provinces, where a lengthy defence of the so-called Romanian bridgehead would be undertaken.

The French and British estimated that Poland should be able to defend the region for two to three months, while Poland estimated it could hold it for at least six months. This Polish plan was based on the expectation that France and the UK would follow through with their treaty commitment and move swiftly to start an offensive of their own. However, neither the French nor British governments made plans to attack Germany while the Polish campaign was still being fought. In addition, they expected the Polish campaign devolve into trench warfare, as had been the case in World War I, so forcing the Germans to sign a peace treaty restoring Poland’s borders. The French and British governments did not inform the Polish authorities, however, and these latter accordingly based their defence plans on the expectation of a quick relief action in the west. The plan to defend the borders contributed vastly to the defeat of Poland, for the nation’s forces were stretched thinly along the very long border and lacked compact lines and good positions in terrain which generally favoured the attack rather than the defence. Thus the German mechanised forces were often able to break though and encircle the Polish forward formations. The Poles' problems were further compounded by their failure to provide adequate protection for the lines of communication. In overall terms, about one-third of the Polish army was grouped in or near the Polish corridor, where it was vulnerably exposed to a double envelopment from East Prussia and Pomerania and thus to being caught in a large pocket. In the south, facing the main thrusts of the German advance, the Polish forces were somewhat more thinly spread. At the same time, nearly another one-third of Poland’s troops were massed in reserve in the north central part of the country, between the major cities of Łódź and Warsaw, under Śmigły-Rydz’s immediate disposal.

The scheme for forward concentration adopted by the Poles effectively lost them the opportunity to fight a series of delaying actions, since the vast bulk of their army moved on foot and was therefore incapable of pulling back to its defensive positions in the rear before it was overrun or encircled by German columns with a greater degree of mechanisation. The political decision to defend the border was thus a major error in strategic terms, but it was not the Poles' only error. Polish propaganda in the pre-war period had averred that any German invasion would be defeated with ease, and thus the succession of Polish reverses along the frontier came as a morale-shattering blow to most of Poland’s civil population, which was wholly unprepared for such news and fled in panic toward the east, spreading chaos, adversely affecting the morale of the troops and jamming the country’s few main roads, which the Polish needed for movement. The Polish propaganda effort also had adverse effects on the Polish troops, whose already thrown into disarray by refugees and the activities of German mobile units operating in the rear, were rendered still more chaotic by palpably false Polish radio broadcasts and press reports reporting imaginary victories. This persuaded some Polish troops to allow themselves to be encircled or to commit themselves to a defence against overwhelming odds in the belief that they were actually counterattacking or were about to be reinforced.

The first overt act of 'Weiss' (i) took place at 04.40 on 1 September, when Luftwaffe aircraft attacked Wieluń, destroying 75% of the town and killing almost 1,200 people, most of them civilians. Five minutes later, at 04.45, the German pre-dreadnought battleship Schleswig-Holstein opened fire on the Polish military depot at Westerplatte, in the Free City of Danzig. At 08.00 German troops, still before the issue of any formal declaration of war, attacked near Mokra, and the battle of the borders had begun. Later on the same day the Germans advanced into Poland across several other sectors of the nation’s northern, western and southern frontiers, and German aircraft began raids on Polish cities.

The Germans' primary offensive axes led to the east from Germany proper through the Polish western border. A second axis was used by supporting attacks from East Prussia in the north, and a third axis was that of the collaborative German and Slovak drive by Čatlos’s Field Army 'Bernolak' from Slovakia. Despite some Polish successes in minor border battles, the Germans' overwhelming numerical strength, in combination with superiority at the technical, operational and tactical levels, forced the Polish armies to withdraw from the borders toward Warsaw and Lwów.

The Luftwaffe gained air superiority early in the campaign. By 3 September, when the 4th Army in the north-west had reached the Vistula river, some 6 miles (10 km) from the German border, and the 3rd Army in the north-east was approaching the Narew river, the Panzer divisions of the 10th Army in the west were already beyond the Warta river, Two days later the 10th Army's left wing was well to the rear of Łódź and its right wing outside Kielce, and by 8 September the Panzer divisions of the XVI Corps (mot.) were on the outskirts of Warsaw after an advance of 140 miles (225 km) during the first week of 'Weiss' (i). The leichte Divisionen on von Reichenau’s right were on the Vistula river between Warsaw and Sandomierz by 9 September, while the 14th Army, in the south, was on the San river above and below Przemyśl. At the same time, Guderian led the armoured formations of his XIX Corps (mot.) having crossed the Polish 'corridor' from the 4th Army to the 3rd Army, across the Narew river, attacking the line of the Bug river and beginning the encirclement of Warsaw from the north-east. All the German armies had made major progress in fulfilling their parts of 'Weiss' (i).

The Polish armies were already collapsed into unco-ordinated fragments, and while some of these were retreating others were delivering disjointed attacks on the German columns nearest them. The Polish forces abandoned the western regions of Pomerania, Greater Poland and Silesia in the first week of the campaign after a series of defeats in the so-called Battle of the Border. Thus the Polish plan for a cordon defence of the nation’s western frontier was completely disastrous in achieving any significant check on the pace of the German advance. The German formations maintained a high tempo of operations, and soon overwhelmed the Polish forces' secondary positions. On 10 September, Śmigły-Rydz ordered a general retreat to the south-east in the direction of the Romanian 'bridgehead'. Meanwhile, the Germans were tightening their encirclement of the Polish forces to the west of the Vistula in the Łódź area and, still farther to the west, round Poznań, and also penetrating deep into the eastern part of Poland.

Under heavy aerial bombardment since the first hours of the war, Warsaw was attacked on 9 September and taken under siege on 13 September. At that time the German spearheads had also reached Lwów, a major metropolis in eastern Poland. Some 1,150 German aircraft bombed Warsaw on 24/35 September in 'Wasserkante' and caused huge damage and considerable loss of life.

The largest battle of the 'Weiss' (i) campaign was the Battle of the Bzura River, otherwise the Battle of Kutno, which was fought near the Bzura river to the west of Warsaw between 9 and 19 September. As noted above, the Polish 'Zavod' plan had called for the defence of Poland’s border regions, and as a result of this Bortnowski’s Pomorze Army found itself in the Polish 'corridor' surrounded by German forces on two fronts, and Kutrzeba’s Poznań Army was pushed to the western edge of Poland, separated from both its primary defensive positions and other Polish armies. 'Weiss' (i) proved the folly of the border defence plan in the first days of the war: the Pomorze Army was defeated in the Battle of Bory Tucholskie and forced to retreat toward the south-east, and the Poznań Army, although not facing heavy German assaults, was forced to retreat to the east as a result of the defeats of its neighbouring formations, namely the Pomorze Army to the north and the Łódź Army to the south; both of these were retreating, leaving the Poznań Army in danger of being flanked and surrounded by the German forces. On 4 September the Poznań Army moved through Poznań and abandoned it to the Germans, although at this point it was not in contact with significant German forces. By 6 September the Pomorze Army and Poznań Army had linked, forming the strongest Polish operational unit in the campaign, and Bortnowski subordinated himself to Kutrzeba.

On 7 September, the Polish forces became aware of the German push towards Łęczyca, which if successful could cut off the Polish forces' line of retreat. By 8 September, the leading German formations had reached Warsaw, marking the beginning of the siege of the Polish capital. At the same time, German forces had lost contact with the Poznań Army, and the German command assumed that the army must have been transported by rail to reinforce the defence of Warsaw. The Germans thus remained unaware of the fact that the Poznań Army had joined the Pomorze Army which, since its defeat in the Battle of Bory Tucholskie, the Germans considered no longer to be a significant threat. On 8 September the Germans were certain that they had eliminated all major Polish resistance in the area to the west of the Vistula river, and were preparing to cross this major water barrier and engage the Polish forces on the eastern side.

Meanwhile, Kutrzeba and his staff officers had suspected, even before the start of 'Weiss' (i), that it would be the armies flanking the Poznań Army which would bear the main weight of the German attack, and had developed plans at an offensive toward the south to relieve the Łódź Army. In the first week of the campaign, however, these plans were rejected by Śmigły-Rydz. By 8 September Kutrzeba had lost contact with Śmigły-Rydz, who had relocated his headquarters from Warsaw to Brest-Litovsk, and therefore decided on his own initiative to proceed with his plan. The situation of his army was dire as German forces were close to completing an encirclement of his formations: the 8th Army had secured the southern bank of the Bzura river, and the 4th Army had secured the northern bank of the Vistula river between Włocławek and Wyszogród, and some of its formations were attacking the rear of the Pomorze Army and Poznań Army from the direction of Inowrocław and crossing the Vistula river near Płock.

In the resulting Battle of the Bzura River the Polish forces comprised the Poznań Army and Pomorze Army, with some 225,000 men in eight infantry divisions and between two and four cavalry brigades, and the German forces included Blaskowitz’s 8th Army and von Reichenau’s 10th Army of Heeresgruppe 'Süd', elements of von Kluge’s 4th Army of Heeresgruppe 'Nord', with air support from Kesselring’s Luftflotte I and Löhr’s Luftflotte IV, with some 425,000 men in 12 infantry divisions and five Panzer and motorised divisions.

The Battle of the Bzura River can be divided into three phases: first, the Polish offensive toward Stryków, aiming at the flank of the 10th Army (9/12 September), second the Polish offensive towards Łowicz (13/15 September), and third the German counterattack and eventual defeat of the Poles, with the latter’s withdrawal toward Warsaw and Modlin (16/19 September).

On the night of 9/10 September, the Poznań Army began its counter-offensive from the area to the south of the Bzura river, its target being the forces of the 8th Army advancing between Łęczyca and Łowicz toward Stryków. Kutrzeba had noticed that the 8th Army northern flank was held only weakly by the 30th Division, which was stretched along an 18.5-mile (30-km) defensive line while the rest of the army was advancing toward Warsaw. The main weight of the Polish counter-offensive was provided by the formations and units under the command of Generał brygady Edmund Knoll-Kownacki, known as the Operational Group 'Knoll-Kownacki' (14th, 17th, 25th and 26th Divisions). The right wing of the offensive, in the area of Łęczyce, included Pułkownik L. Strzelecki’s Podolska Cavalry Brigade, and its left wing, advancing from Łowicz to the area of Głowno, Generał brygady Roman Abraham’s Wielkopolska Cavalry Brigade. These groups inflicted considerable losses on the Germans of the 30th Division and neighbouring 24th Division, which lost 1,500 men killed or wounded and 3,000 taken prisoner. Boosted by the presence of TKS and TK-3 reconnaissance tankettes, the cavalry brigades moved to threaten the flanks and rear of the advancing German units.

The German forces were thrown back about 12.5 miles (20 km), and the Poles recaptured several towns, including Łęczyca and Piątek, as well as the village of Góra Świętej Małgorzaty. On 10 September, the 17th Division met the 17th Division at Małachowicze. On the next day the Polish forces continued their attack, advancing on Modlna, Pludwiny, Osse and Głowno.

Initially underestimating the threat of the Polish advance, the Germans decided on 11 September to redirect the main force of the 10th Army, 4th Army and reserves of Heeresgruppe 'Süd', supported by Luftflotte IV's warplanes, toward the Bzura river. These German forces included the 1st Panzerdivision, 4th Panzerdivision and newly formed SS Infanterieregiment 'Leibstandarte Adolf Hitler' (mot.). German air superiority proved a decisive factor, making it very costly and difficult for the Poles to move units during the day. On the following day the Poles reached the line lining Stryków and Ozorków, and on the same day Kutrzeba learned that units of the Łódź Army to his south had retreated to the fortress of Modlin, and decided to stop his offensive, instead looking for a way to break through Sochaczew and the Kampinos forest in order to reach Warsaw.

On the morning of 14 September, Bortnowski’s 26th and 16th Divisions crossed the Bzura river near Łowicz, and the 4th Division reached the road linking Łowicz and Głowno. At this point Bortnowski ordered the 26th Division to retreat: he had learned of the withdrawal of the 4th Panzerdivision from the outskirts of Warsaw, and was concerned that this Panzer division posed a threat to his men.

On 15 and 16 September, the Pomorze Army assumed a defensive posture on the northern bank of the Bzura river. An improvised infantry grouping commanded by Generał brygady Stanisław Grzmot-Skotnicki, commander of the Operational Group 'Czersk', was in the area between Kutno and Punchline, Generał brygady Michał Karaszewicz-Tokarzewski’s units near Gąbin, and parts of the Poznań Army along the Bzura river near Sochaczew, and these were ready to begin their drive to the east in the direction of Warsaw. To encircle and destroy the Polish forces, the Germans used most of the 10th Army, including two Panzer, one motorised and three light divisions with some 800 tanks. The attack on the encircled Polish forces began on 16 September with major Luftwaffe air support. On 15 September Poles were driven from Sochaczew, a town on the Bzura river, and trapped in a triangular area bounded by the Bzura river, Vistula river and the German forces. After crossing the Bzura between Sochaczew and Brochów and engaging the 25th Division, the 1st Panzerdivision took Ruszki, but its advance was then halted. The Poles started to cross the Bzura river near its confluence with the Vistula river to the north of Sochaczew, being forced to abandon most of their heavy equipment in the process, and then retreated toward Warsaw. On 17 September, German heavy artillery was shelling the crossing point to the north of Brochów, and the largest air operation of the campaign began as the Luftwaffe savaged the retreating Polish forces.

During the night of 17/18 September, the main strength of the Poznań Army attacked the German forces in order to break out of the German encirclement between Witkowice and Sochaczew. The 15th Division and Podolska Cavalry Brigade again crossed the Bzura river at Witkowice. In Brochów, the 25th and 17th Divisions crossed the Bzura river. The 14th Division was concentrated in Łaziska. At the same time, the Pomorze Army moved toward the villages of Osmolin, Kierozia and Osiek.

In the morning the Germans started their drive toward the south along both banks of the Bzura river with the support of more than 300 aircraft and substantial quantities of heavy artillery. Taking advantage of their position on the high ground of the Vistula river’s right bank, the German howitzers shelled Polish positions for the entire day. After two days of heavy fighting, and now without ammunition and food, the Poles knew that further attempts at a major break-out were impossible. Only a few Polish units managed to break out of the encirclement. These groups reached Warsaw and Modlin, mostly around 19 and 20 September, after traversing the Kampinos forest, and fighting German units in the area in, for example, the Battle of Wólka Węglowa. Kutrzeba, Knoll-Kownacki and Tokarzewski escaped, as did the Wielkopolska and Podolska Cavalry Brigades of Abraham’s command, and the 15th and 25th Divisions. Those formations which did not cross the river (4th, 14th, 17th, 26th and 27th Divisions) and Bortnowski surrendered between 18 and 22 September. The Polish losses were estimated at 18,000 and 20,000 men killed including Generał brygady Franciszek Wład, Grzmot-Skotnicki and Generał brygady Mikołaj Bołtuć), 32,000 men wounded and 170,000 men taken prisoner. The German casualties were estimated at 8,000 men killed, 4,000 men taken prisoner, 50 tanks knocked out, and 20 pieces of artillery lost.

After the end of the Battle of the Bzura Rover the remaining German divisions drove forward as rapidly as they could toward Warsaw and Modlin, and soon encircled both of these Polish cities. The Bzura river campaign had ended with a Polish defeat, but the Poles' initial local successes had stalled the German advance on Warsaw for several days and forced the Germans to divert formations from their push towards Warsaw, and this enabled the Polish formations and units defending Warsaw and the area round it to improve their defence of the Polish capital, although this was only an impediment to the Germans' final seizure of Warsaw. After this defeat, Poland lost its ability to take the initiative and indeed to undertake anything in the way of large-scale counterattacks, let alone strategic counter-offensives.

The government of President Ignacy Mościcki and the high command had left Warsaw in the first days of the campaign and headed to the south-east, reaching Brześć on 6 September. Śmigły-Rydz ordered the Polish forces to retreat in the same direction, behind the Vistula and San rivers, beginning the preparations for the long defence of the Romanian bridgehead area.

From the beginning of the Polish campaign the German government repeatedly asked Stalin and Molotov to act upon the August agreement and attack Poland from the east. After the agreement reached by Vyacheslav Molotov and Shigenori Togo, the Soviet and Japanese foreign ministers, ended Soviet/Japanese hostilities in the Far East on 16 September, concerned about the high speed and rapid gains of the German advance, and avid to seize its allotted share of Poland, the USSR committed its forces against eastern Poland on 17 September.

Like the Germans, the Soviets advanced on two primary axes, each managed by a front. The commander of each of the two fronts, to the north and south of the Pripyet marshes, had at his disposal a mobile group of forces created from cavalry and mechanised troops, and the effects of the Stalinist purges of the late 1930s on the officer corps are all too evident: there was only one army commander serving in the appropriate rank of army general, in this case 2nd class (Komandarm 2nd rank), the rest being of corps commander (Komcor) and divisional commander (Komdiv) status.

The two primary Soviet formations were Komandarm 2nd rank Mikhail P. Kovalev’s Belorussian Front 4 and Komandarm 1st rank Semyon K. Timoshenko’s Ukrainian Front 5 with an initial strength of 466,515 men rising to 800,000 men in 33 or more divisions and 11 or more brigades with 4,735 tanks, 4,960 pieces of artillery and 3,300 aircraft.

It had been agreed that the USSR would relinquish its interest in the territories between the new border and Warsaw in exchange for inclusion of Lithuania in the Soviet 'zone of interest'. By 17 September 1939 the Polish defence was already broken and Poland’s only hope was for its surviving forces to retreat and reorganise along the front of the Romanian bridgehead. However, these plans were rendered obsolete nearly overnight, when the two Soviet fronts attacked, to the north and south of the Pripyet marshes respectively in the case of the Belorussian Front and Ukrainian Front respectively, to overrun eastern Poland against only the sketchiest of defences found by the Korpus Ochrony Pogranicza, consisting of a mere 25 battalions.

This Soviet aggression violated the Riga Peace Treaty of 18 March 1921 to end the Soviet-Polish War, the Soviet-Polish Non-Aggression Pact and other international treaties, both bilateral and multilateral but, like the Germans, the Soviets had a neat and wholly false rationale available for their actions: they were 'protecting the Ukrainian and Belorussian minorities of eastern Poland in view of the imminent Polish collapse'. Śmigły-Rydz ordered the Polish defence cordon in the east to fall back and not to engage the Soviets, but there nevertheless took place some clashes and small battles, such as the Battle of Grodno, as soldiers and members of the local population attempted to defend the city. The Soviets murdered a large number of Poles, including prisoners of war such as Generał brygady Józef Olszyna-Wilczyński. The Organisation of Ukrainian Nationalists also rose against the Poles, and communist partisans organised local revolts in places such as Skidel, robbing and murdering Poles.

The Soviet invasion was one of the decisive factors in convincing the Polish government that the war was lost for, as noted above, before the Soviet offensive the Polish military’s fallback plan had called for long-term defence against Germany in the south-eastern part of Poland while awaiting relief from an offensive by the Western Allies on Germany’s western border. The Polish government refused to surrender or negotiate a peace with Germany, however, and ordered all formations and units which could do so to evacuate themselves from Poland and reorganise in France. Meanwhile, Polish forces tried to move toward the Romanian bridgehead area, still actively resisting the German invasion. From 17 to 20 September the Kraków Army and Lublin Army were crippled in the Battle of Tomaszów Lubelski, which was the second largest battle of the campaign. Lwów capitulated on 22 September in a turn of events illustrative of the bizarre turn of events resulting from the Soviet intervention: the city had been attacked by the Germans more than a week earlier, and in the middle of the siege the Germans handed over to their Soviet allies.

Despite a series of intensifying German attacks, Warsaw, defended by quickly reorganised retreating units, civilian volunteers and militia, held out until its capitulation on 28 September after the massive 'Wasserkante' bombing of 25 September. The fortress area of Modlin to the north of Warsaw capitulated on 29 September after an intense 16-day battle. Some isolated Polish garrisons managed to hold their positions long after being surrounded by German forces. The Westerplatte enclave’s tiny garrison capitulated on 7 September, the Oksywie garrison held out until 19 September, and Hel’s defence lasted to 2 October.

Despite a Polish victory at the Battle of Szack, after which the Soviets executed all the officers and non-commissioned officers they had managed to capture, the Soviet forces reached the line of Narew, Western Bug, Vistula and San rivers by September 28, in many cases meeting German units advancing from the west. The last Polish operational unit, Generał dywizji Franciszek Kleeberg’s Independent Operational Group 'Polesie', surrendered after the four-day Battle of Kock near Lublin on 6 October, marking the end of 'Weiss' (i).

This campaign presaged the type of total warfare which would become a feature of World War II. Civilian casualties were high during and after combat, and from the start of the German offensive the Luftwaffe had attacked civilian targets and columns of refugees along the roads to wreak physical havoc, disrupt communications and destroy Polish morale. And quite separate from battle casualties, the German forces (both SS and the regular army) are accused of the mass murder of several thousands of Polish prisoners of war and civilians. During a pre-planned 'Tannenberg', almost 20,000 Poles were shot in 760 mass execution sites by the Einsatzgruppen 'special units', in addition to regular army, SS and Selbstschutz units. In round terms, the losses of the Polish civil population amounted to some 150,000 persons, while German civilian losses amounted to some 5,000 persons. At the end of the campaign, Poland was divided between Germany, the USSR, Lithuania and Slovakia. Of those parts controlled by Germany, some were annexed into Germany, while the rest were governed by the so-called General Gouvernement. On September 28, another secret German-Soviet protocol modified the arrangements of August: all of Lithuania was to become a Soviet rather than German sphere of influence, but the dividing line between Germany and the USSR in Poland was moved, in Germany’s favour, as far to the east as the Bug river.

The Polish military losses to the Germans were about 66,000 men killed, 133,700 men wounded and 420,000 men taken prisoner, and to the Soviets between 3,000 and 7,000 men killed, as many as 20,000 men wounded and, depending on source, between 99,150 and 240,000 men taken prisoner.

The German losses were 16,343 men killed, 30,300 men wounded and 3,500 men missing, those of Slovakia 37 men killed, 114 men wounded and 11 men missing, and those of the USSR between 1,475 and 3,000 men killed, between 2,385 and 10,000 men wounded, and an unspecified number of men missing.

As many as 120,000 Polish troops managed to escape to neutral Romania (through the Romanian bridgehead) and Hungary, and another 20,000 escaped to Latvia and Lithuania, with the majority eventually making their way to France or the UK. Most of the Polish navy had already succeeded in reaching the UK.

While the German manpower losses were considerably smaller than those of the Poles, the loss of approximately 30% of Germany’s armoured fighting vehicle strength combined with aircraft losses became the main reason for the German decision to discard its plan for any immediate attack against the French and British on the Western Front.

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The army group’s left flank comprised General Georg von Küchler’s 3rd Army with General Walter Petzel’s I Corps (Generalleutnant Max Bock’s 11th Division, Generalleutnant Siegfried Hänicke’s 61st Division and Generalmajor Werner Kempf’s Panzerverband 'Kempf'), General Nikolaus von Falkenhorst’s XXI Corps (Generalleutnant Hans-Kuno von Both’s 21st Division and Generalleutnant Hans Suttner’s 228th Division), Generalleutnant Albert Wödrig’s Armeekorps 'Wodrig' (Generalleutnant Joachim von Korzfleisch’s 1st Division and Generalleutnant Ludwig von der Layen’s 12th Division) and Wodrig’s Führungstab zbV 1 (Generalleutnant Joachim von Korzfleisch’s 1st Division [mot.]) in East Prussia with the task of destroying the Polish forces in the 'corridor' and with an advance toward Warsaw and the line of the Vistula river’s upper reaches, and Generalleutnant Fritz Brand’s Korps 'Brand' (Generalmajor Offenbacher’s Infanteriebrigade 'Lötzen' and Generalmajor Notle’s Infanteriebrigade 'Goldap') for the defence of East Prussia’s border. The 3rd Army's reserves comprised Generalleutnant Richard Baltzer’s 217th Division and Generalmajor Kurt Feldt’s 1st Kavalleriebrigade.

The right flank comprised General Günther von Kluge’s 4th Army with a corps of frontier guards centred on Generalleutnant Karl von Tiedemann’s 207th Division to protect the Pomeranian frontier, General Adolf Strauss’s II Corps (Generalleutnant Walter Lichel’s 3rd Division and Generalleutnant Franz Böhme’s 32nd Division), General Curt Haase’s III Corps (Generalleutnant Konrad Sorsche’s 50th Division and Generalmajor Eccard Freiherr von Gablenz’s Infanteriebrigade 'Netze') and General Heinz Guderian’s XIX Corps (mot.)(Generalleutnant Leo Freiherr Geyr von Schweppenburg’s 3rd Panzerdivision, Generalleutnant Paul Bader’s 2nd Division [mot.] and Generalleutnant Muritz von Wiktorin’s 20th Division [mot.] and the Panzer-Lehr-Abteilung) in Pomerania with the primary task of destroying the Polish forces in the 'corridor' and advancing up the lower reaches of the Vistula river. The 4th Army's reserves comprised Generalleutnant Walter Graf von Brockdorff-Ahlefeldt’s 23rd Division and Generalleutnant Waldemar Freiherr Grote’s 218th Division.

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The northernmost of the main groupings was General Johannes Blaskowitz’s 8th Army with General Wilhelm Ulex’s X Corps (Generalleutnant Friedrich Olbricht’s 24th Division and Generalleutnant Kurt von Briesen’s 30th Division) and General Maximilian Reichsfreiherr von Weichs’s XIII Corps (Generalleutnant Conrad von Cochenhausen’s 10th Division, Generalleutnant Herbert Loch’s 17th Division plus SS-Obergruppenführer und General der Waffen-SS Josef Dietrich’s motorised SS Regiment 'Leibstandarte SS Adolf Hitler') in northern Silesia with the task of encircling the Polish forces in the region of Kutno. The 8th Army had no reserves.

In the centre was General Walter von Reichenau’s 10th Army with General Viktor von Schwedler’s IV Corps (Generalleutnant Erik Hansen’s 4th Division and Generalleutnant Paul von Hase’s 46th Division), General Emil Leeb’s XI Corps (Generalleutnant Friedrich-Karl Cranz’s 18th Division and Generalleutnant Günther Schwantes’s 19th Division), General Hermann Hoths XV Corps (mot.) (Generalleutnant Georg Stumme’s 2nd leichte Division), General Erich Hoepners XVI Corps (mot.) (Generalleutnant Rudolf Schmidts 1st Panzerdivision, Generalleutnant Peter Weyers 14th Division and Generalleutnant Rudolf Kämpfe’s 31st Division) and General Gustav von Wietersheims XIV Corps (mot.) (Generalleutnant Georg-Hans Reinhardt’s 4th Panzerdivision, Generalleutnant Moritz von Faber de Faur’s 13th Division [mot.] and Generalleutnant Joachim Lemelsen’s 29th Division [mot.]) in southern Silesia with the task of driving north-east straight through Wieluń and Łódź to Warsaw. The 10th Armys reserves amounted to Generalmajor Friedrich-Wilhelm von Loeper’s 1st leichte Division and Generalmajor Adolf-Friedrich Kuntzen’s 3rd leichte Division.

In the south was Generaloberst Wilhelm List’s 14th Army with General Ernst Busch’s VIII Corps (Generalleutnant Heinrich von Vietinghoff-Scheel’s 5th Panzerdivision, Generalleutnant Rudolf Koch-Erpach’s 8th Division, Generalleutnant Hans von Obstfelder’s 28th Division, Generalleutnant Ferdinand Neuling’s 239th Division, and SS-Standartenführer Karl-Maria Demelhuber’s SS Regiment 'Germania' [mot.]), General Werner Kienitz’s XVII Corps (Generalleutnant Eugen Ott’s 7th Division, Generalleutnant Albrecht Schubert’s 44th Division and Generalleutnant Friedrich Materna’s 45th Division), and General Eugen Beyer’s XVIII Corps (Generalleutnant Rudolf Veiel’s 2nd Panzerdivision, Generalleutnant Dr Alfred Ritter von Hubicki’s 4th leichte Division and Generalleutnant Eduard Dietl’s 3rd Gebirgsdivision in Slovakia) with the task of advancing though the Carpathian mountains to crush the Polish forces around Kraków and Przemyśl. The 14th Army's reserves comprised General Ewald von Kleist’s XXIII Corps (Generalleutnant Valentin Feurstein’s 2nd Gebirgsdivision).

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Facing the 3rd Army was Generał brygady Czesław Młot-Fijałkowski’s Independent Operational Group 'Narew' located between Augustów and Poznań with the 18th and 33rd Divisions, and the Podlaska and Suwalska Cavalry Brigades; and Generał brygady Emil Krukowicz-Przedrzymirski’s Modlin Army created on 23 March 1939 with the 8th and 20th Divisions, the Nowogródzka and Mazowiecka Cavalry Brigades, and the Warsaw National Defence Brigade. Between the 3rd Army and 4th Army was Generał dywizji Władysław Bortnowski’s Pomorze Army, which had been created on 23 March 1939 to defend Toruń and Bydgoszcz, and to implement delaying actions in the Polish corridor with a core strength of the 9th, 15th and 27th Divisions, and the Pomeranian and Chełm National Defence Brigades supplemented by Generał brygady Mikołaj Bołtuć's Operational Group 'East' (4th and 16th Divisions) and Pułkownik Stanisław Grzmot-Skotnicki’s Operational Group 'Czersk' (Pomeranian Cavalry Brigade and the Chojnice and Kościerzyna Independent Units). Opposite the right wing of the 4th Army and the left wing of the 8th Army, and located in the salient centred on Poznań, was Generał brygady Tadeusz Kutrzeba’s Poznań Army, which was to attack the flanks on any German breakthroughs to its north and south before falling back toward the prepared defence lines along the Warta river. This army comprised the 14th, 17th, 25th and 26th Divisions, and the Wielkopolska and Podolska Cavalry Brigades. Opposite the right wing of the 8th Army and left wing of the 10th Army, and based round Wieluń, was Generał dywizji Juliusz Karel Wilhelm Józef Rómmel’s Łódź Army, which had been created on 23 March 1939 as the connection between the Kraków and Poznań Armies to its south and north respectively. However, as a result of mistakes by Rómmel, the army was located too close to the German border and joined fighting from the very beginning of the campaign, which deprived it of any possibility of co-operating with its neighbouring formations. This army comprised the 2nd, 10th, 18th and 30th Divisions, the Kresowa and Wołyńska Cavalry Brigades, and the Sieradz National Defence Brigade. Facing the centre and right of the 10th Army as well as the left of the 14th Army, and therefore centred on Kraków, was Generał brygady Antoni Szylling’s Kraków Army, created on 23 March 1939 as the main pivot of the Polish defence. Its primary task was to delay the advancing German troops before withdrawing to the east along the northern side of the Carpathian mountains. The army’s core formations and units were the 6th, 7th and 11th Divisions, the Krakówska Cavalry Brigade and the 10th Motorised Cavalry Brigade, with further strength added by Generał brygady Jan Jagmin-Sadowski’s Operational Group 'Śląsk' (23rd and 55th Divisions) and Generał brygady Mieczysław Boruta-Spiechowicz’s Operational Group 'Bielsko' (21st Mountain Division and 1st Mountain Brigade). Finally, located between Przemyśl and Tarnów in the south of Poland opposite the 14th Army and the Field Army 'Bernolak' was Generał brygady Kazimierz Fabrycy’s Carpathian Army, which had been created on 11 July 1939 after the German annexation of Czechoslovakia and creation of the puppet state of Slovakia. The main task of this army was to secure mountain passes in the Carpathians. Initially the army consisted of two extemporised mountain brigades and a number of smaller units, but later in the course of war was joined by forces of the withdrawing Kraków Army. The core units were the 2nd and 3rd Mountain Brigades, the Carpathian Half-Brigade of National Defence, the 2nd Regiment of the Border Defence Corps, the 1st Motorised Artillery Regiment, and the 9th Heavy Artillery Regiment. Attached to the Carpathian Army was the Kaw Group (Warsaw Mechanised Brigade, and 46th and 47th Light Artillery Regiments), and the Polish mobilisation plan also called for the creation of the Tarnów Group (22nd and 38th Divisions).
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The Belorussian Front included four armies and was the northern of the two fronts, and on 17 September comprised Komkor Vasili I. Kuznetsov’s 3rd Army of one corps and one operational group in the form of the IV Corps (27th and 50th Divisions) and the Lepelska Group (5th Division, 24th Cavalry Division, and 22nd and 25th Tank Brigades); Komdiv Nikofor V. Medvedev’s 11th Army of two corps in the form of the XVI Corps (2nd and 100th Divisions) and the III Cavalry Corps (7th and 36th Cavalry Divisions, and 3rd Light Tank Brigade); Komcor Ivan V. Boldin’s Cavalry-Mechanised Group with three corps in the form of the V Corps (4th, 13th and 33rd Cavalry Divisions, and 16th Light Tank Brigade), the VI Cavalry Corps (4th, 6th and 11th Cavalry Divisions), and the XV Tank Corps (2nd, 21st and 27th Tank Brigades, and 20th Motorised Rifle Brigade); and Komkor Ivan G. Zakharkin’s 10th Army with one corps in the form of the XI Corps (6th, 33rd and 121st Divisions); Komdiv Vasili I. Chuikov’s 4th Army with two corps in the form of the VIII Corps (29th and 32nd Tank Brigades) and the XXIV Corps (52nd Division and Dniepr Military Flotilla).
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The Ukrainian Front included three armies and was the southern of the two fronts, and on 17 September comprised Komdiv Ivan G. Sovetnikov’s 5th Army with two corps in the form of the XV Corps (45th and 60th Divisions) and the VIII Corps (44th and 81st Divisions, and 36th Tank Brigade); Komcor Filipp I. Golikov’s 6th Army with two corps in the form of the II Cavalry Corps (3rd, 5th and 14th Cavalry Divisions, and 24th Light Tank Brigade) and the XVII Corps (96th and 97th Divisions, and 10th and 38th Tank Brigades); and Komandarm Ivan V. Tyulenev’s 12th Army with four corps in the form of the XIII Corps (72nd and 99th Divisions) and, from 28 September, the Front Cavalry Group (IV Cavalry Corps with the 32nd and 34th Cavalry Divisions as well as the 26th Independent Tank Brigade, the V Cavalry Corps with the 9th and 16th Cavalry Divisions as well as the 23rd Independent Tank Brigade, and the XXV Tank Corps with the 4th Light Tank Brigade, 5th Tank Brigade and 1st Motor Rifle Brigade).