'Braunschweig' (i) was the German redesignation of 'Blau', the most northern element of the three-part strategic offensive of the summer of 1942 (28 June/22 July 1942).

The operation was a continuation of the strategic thinking behind the previous year’s 'Barbarossa', intended to knock the USSR out of the war. The operation was initially designated as 'Blau', and this is the name by which the whole of the Germans' strategic summer offensive of 1942 is generally known. The name was changed from 'Blau' to 'Braunschweig' (i) on 30 June, and the plans following the original 'Blau' (originally named 'Blau I' and 'Blau II' were renamed as 'Clausewitz' and 'Dampfhammer': the former detailed the beginning of the operations of Heeresgruppe 'A' in July, and 'Dampfhammer' the follow-up operations later in July.

In his Führerweisung Nr 45 of 23 July, Adolf Hitler outlined new goals for 'Braunschweig' (i): the German forces were to advance toward the Caucasus in 'Edelweiss' and Stalingrad in 'Fischreiher'. Thus the forthcoming offensive involved a two-pronged attack: one from the Axis right flank against the oilfields of Baku and known as 'Edelweiss', and the other from the left flank in the direction of Stalingrad along the Volga river, known as 'Fischreiher'.

Hitler had personally intervened in the plans for this operation, and ordered that Heeresgruppe 'Süd' create Generalfeldmarschall Wilhelm List’s Heeresgruppe 'A' and Generaloberst Maximilian Freiherr von Weichs’s Heeresgruppe 'B'. This division of the army group had occasioned great alarm in the German general staff, and Hitler was warned repeatedly about the dangers inherent in any such division of command and strength. Complaints from the field commanders caused Hitler to dismiss and replace von Bock on 15 July. Later studies confirmed this split to be one of the main causes for the eventual demise of Generalfeldmarschall Friedrich Paulus’s 6^th Army in Stalingrad. Hitler persisted in this division of Heeresgruppe 'Süd' for apparently valid strategic reasons: the acquisition of the oilfields in the Caucasus region, and the severance of the Soviet supply transports along the Volga river through Stalingrad.

On 23 July, Hitler met with Viktor Lutze, commander of the Sturmabteilung, and Obergruppenführer und General der Waffen-SS Hans Jüttner, the SS chief-of-staff, and the three men discussed several matters. The most important of these was Führerweisung Nr 45, which was a continued 'Braunschweig' (i). In this meeting Hitler stated several directives that 'Heeresgruppe 'A' [is to] take the Caucasus and Baku ['Edelweiss'], while Heeresgruppe 'B' [is] to conquer Stalingrad and, if possible, Astrakhan. Heeresgruppe 'Nord' [is] instructed to conquer Leningrad ['Feuerzauber'].'

The directive said: 'In a campaign of little more than three weeks, the ultimate goal I had set the south wing of the eastern front has already been accomplished. Only some rather weak [Soviet] forces belonging to the armies of Semyon Timoshenko have managed to escape the envelopment and reach the bank of the Yuzhny Don river. These will presumably receive reinforcements from the Caucasus area…Currently the enemy is massing another army group in the Stalingrad area, where stiff resistance is to be expected.'

von Bock’s Heeresgruppe 'Süd' was then split into Heeresgruppe 'A' and Heeresgruppe 'B'. Heeresgruppe 'A' was tasked with crossing the Caucasus mountains to reach the oilfields in the Baku area on the western side of the Caspian Sea, while Heeresgruppe 'B' protected the operation’s flank along the Volga river. Supported by 2,035 Luftwaffe aircraft and 1,934 tanks and assault guns, the 1,370,287 men of what had been Heeresgruppe 'Süd' attacked on 28 June, advancing 30 miles (48 km) on the first day and easily brushing aside the 1,715,000 Soviet troops, who erroneously expected a German offensive on Moscow even after the start of 'Blau'. The Soviet collapse in the south allowed the Germans to capture the western part of Voronezh on 6 July and reach and cross the Don river near Stalingrad on 26 July. The approach of Heeresgruppe 'B' toward Stalingrad slowed at a time late in July and early in August as a result of constant counterattacks by newly deployed Soviet reserves and the overstretched German lines of communication. The Germans defeated the Soviets in the Battle of Kalach and the combat shifted to the city itself late in August. Incessant Luftwaffe air attacks, artillery fire and street-to-street combat completely destroyed the city and inflicted heavy casualties on the opposing forces. After three months of battle, the Germans controlled 90% of Stalingrad on 19 November.

In the south, Heeresgruppe 'A' captured Rostov-na-Donu on 23 July and swept to the south from the Don river into the Caucasus, capturing the demolished oilfields at Maykop on 9 August and Elista on 13 August near the coast of the Caspian Sea. Heavy Soviet resistance, sabotage operations in occupied Poland, and the long distances from Axis sources of supply reduced the Axis offensive to local advances only and prevented the Germans from completing their strategic objective of capturing the main Caucasian oilfield at Baku. Luftwaffe bombers destroyed the oilfields at Grozny, but attacks on Baku were prevented by German fighters' lack of range.

The Allies were concerned about the possibility of German forces continuing to the south and east, and there linking with Japanese forces (then advancing in Burma) in India. However, the Soviets defeated the Germans at Stalingrad, following 'Uran' and 'Maly Saturn'. This defeat forced the Axis forces to retreat from the entire Caucasus region except the Kuban area, which remained tentatively occupied by Axis troops.

On 22 June 1941 the Germans and their allies had launched 'Barbarossa' with the intention of defeating the Soviets in a Blitzkrieg campaign lasting only a few months. The Axis offensive had met with initial success and the Soviets had suffered a number of major defeats before halting the Axis units just short of Moscow in November and December 1941. Although the Germans had captured vast areas of land and important industrial centres, the USSR remained firmly in the war. In the winter of 1941/42 the Soviets struck back in a series of successful counter-offensives, pushing back the German threat to Moscow. Despite these setbacks, Hitler wanted an offensive solution, for which he required the oil resources of the Caucasus. By February 1942 the Oberkommando des Heeres had begun to develop plans for a follow-up campaign to the aborted 'Barbarossa', with the Caucasus as its principal objective. On 5 April 1942, Hitler laid out the elements of the plan now known as 'Blau' in his Führerweisung Nr 41, which itemised the main goals of the forthcoming summer campaign on the Eastern Front: holding attacks by Heeresgruppe 'Mitte', the capture of Leningrad and the establishment of a firm terrestrial link with Finland by Heeresgruppe 'Nord', and the capture of the Caucasus region by Heeresgruppe 'Süd'. The primary German focus was the capture of the Caucasus region.

The Caucasus, a large, culturally and geographically diverse region bisected by its eponymous mountain range, is bounded by the Black Sea to the west and the Caspian Sea to the east. The region north of the mountains was used largely for the growing of grain, cotton and heavy farm machinery, while its two main oilfields, at Maykop, near the Black Sea, and Grozny, about mid-way between the Black Sea and the Caspian Sea, produced about 10% of all Soviet oil. To the south of the mountains lay Transcaucasia, comprising Georgia, Azerbaijan and Armenia. This heavily industrialised and densely populated area contained some of the largest oilfields in the world. Baku, the capital of Azerbaijan, was one of the richest, producing 80% of the USSR’s oil, amounting to about 24 million tons in 1942 alone.

The Caucasus also possessed plentiful coal and peat, as well as non-ferrous and rare metals. Manganese deposits at Chiaturi, in Transcaucasia, formed the richest single source in the world, yielding 1.5 million tons of manganese ore annually, 50% of the USSR’s total production. The Kuban region of the Caucasus also produced large amounts of wheat, corn, sunflower seeds and sugar beet, all essential in the production of food.

These resources were of immense importance to Hitler and the German war effort. Of the three million tons of oil Germany consumed per year, 85% was imported, mainly from the USA, Venezuela and Iran. When war broke out in September 1939, the British naval blockade cut Germany off from the Americas and the Middle East, leaving the country reliant on oil-rich European countries such as Romania to supply the resource. An indication of German reliance on Romania is evident from its oil consumption: in 1938, just 33% of the 7.5 million consumed by Germany came from domestic stocks. Oil had always been one of Germany’s most vulnerable war-making requirements, and by the end of 1941 Hitler had nearly exhausted Germany’s reserves, which left him with only two significant sources of oil, namely the country’s own production of synthetic oils and the Romanian oilfields, with the latter supplying 75% of Germany’s oil imports in 1941. Aware of his declining oil resources, and fearful of Allied and Soviet air attacks on Romania, Hitler’s strategy was increasingly driven by the need to protect Romania and acquire new resources, which were essential if he wanted to continue waging a prolonged war against a growing list of enemies. Late in 1941, the Romanians warned Hitler that their stocks were exhausted and they were unable to meet German demands. For these reasons, the Soviet oilfields were extremely important to Germany’s industry and armed forces as the war became global, the power of the Allies grew, and shortages started to occur in Axis resources.

The German offensive was to be conducted across the southern Russian steppe using the strength of the following formations: Heeresgruppe 'A' (1^st Panzerarmee, 17^th Army, Romanian 3^rd Army and 11^th Army); Heeresgruppe 'B' (2^nd Army, 4^th Panzerarmee, 6^th Army, Hungarian 2^nd Army, Romanian 4^th Army and Italian 8^th Army; and Luftflotte IV (IV Fliegerkorps and VIII Fliegerkorps). The German air strength in the east numbered 2,644 aircraft on 20 June 1942, a figure 20% greater than that of one month earlier. Whereas in 1941 most units fought on the central front supporting Heeresgruppe 'Mitte', 1,610 aircraft (61%) supported Heeresgruppe 'Süd'. Initially commanded by Generaloberst Alexander Löhr, on 20 July 1942 Generaloberst Wolfram Freiherr von Richthofen took command of Luftflotte IV.

The German plan involved a three-stage attack: 'Blau I' was the responsibility of the 4^th Panzerarmee commanded by Generaloberst Hermann Hoth and transferred from Heeresgruppe 'Mitte', and the 2^nd Army supported by Altábornagy Gusztáv Jány’s Hungarian 2^nd Army, and these were to attack from Kursk to Voronezh and continue the advance, anchoring the northern flank of the offensive toward the Volga river; 'Blau II' was the responsibility of Generaloberst Friedrich Paulus’s 6^th Army, and this was to attack from Kharkov and, moving in parallel with the 4^th Panzerarmee, to reach the Volga river at Stalingrad, whose capture was not at that time deemed necessary; and 'Blau III' was the responsibility of the 1^st Panzerarmee and would then strike to the south in the direction of the lower reaches of the Don river with the 17^th Army on the western flank and the Romanian 4^th Army on the eastern flank.

The operations' strategic objectives of the operation were the oilfields at Maykop, Grozny and Baku. As in 'Barbarossa', these movements were expected to result in a series of grand encirclements of Soviet troops.

The Stavka (Soviet army command) failed to discern the direction of the main German strategic offensive which it anticipated for the summer of 1942, even though it were in possession of the German plans: on 19 June a reconnaissance aeroplane carrying Major Joachim Reichel, the 23^rd Panzerdivision's chief of operations, was shot down over Soviet-held territory over the front near Kharkov, the Soviets then recovering from the crashed aeroplane several maps detailing the exact German plans for 'Blau', and passing these up the chain of command to the Stavka in Moscow. Iosif Stalin believed the maps to be a German ruse, however, and remained sure that the primary German strategic goal in 1942 would again be Moscow, in part as a result of 'Kreml', a German deception plan aimed at the city. As a result, a majority of the Soviet Soviet forces were deployed in the area of Moscow, although the direction from which the 'Blau' offensive would come was still defended by the Bryansk Front, South-West Front, South Front and 'North Caucasus Front'. With about 1 million men at the front line and another 1.7 million in reserve armies, their forces amounted to about 25% of all Soviet troops. Following the disastrous start of 'Blau', the Soviets reorganised their front line several times. Over the course of the campaign, the Soviets also fielded the Voronezh Front, Don Front, Stalingrad Front, Trans-Caucasus Front and Caucasus Front, though not all of these existed at the same time.

With the German thrust expected in the north, the Stavka planned several local offensives in the south to weaken the Germans. The most important of these was aimed at the city of Kharkov and would be conducted mainly by the South-West Front commanded by Marshal Sovetskogo Soyuza Semyon K. Timoshenko, supported by the South Front commanded by General Leytenant Rodion Ya. Malinovsky. The Soviet operation was scheduled for 12 May, just before the start of the German offensive planned for this area. The resulting '2^nd Battle of Kharkov' ('Izyum Bridgehead Offensive Operation') ended in disaster for the Soviets, severely weakening their mobile forces. At the same time, the Axis clearance of the Kerch peninsula and the Battle of Sevastopol, which lasted until July, weakened the Soviets still further and allowed the Germans to supply Heeresgruppe 'A' across the Strait of Kerch from the Kerch peninsula to the Kuban.

The German offensive was launched on 28 June, with 4^th Panzerarmee starting its drive toward Voronezh. As a result of the chaotic Soviet retreat, the Germans were able to advance rapidly, restoring German confidence for the imminent major offensive.

Well-honed close air support by the Luftwaffe also played a key part in this early success. German warplanes contained the improving but still inferior Soviet air forces, through air superiority operations, and provided interdiction through attacks on airfields and Soviet defence lines. At times, the German air arm acted as a spearhead rather than a support force, ranging on ahead of the armour and infantry to disrupt and destroy Soviet defensive positions. As many as 100 German aircraft were concentrated on a single Soviet division in the path of the spearhead during this phase. General Major Mikhail I. Kazakov, the Bryansk Front’s chief-of-staff, noted the strength and effectiveness of the Axis aviation, and this is reflected in the fact that within 26 days, the Soviets lost 783 aircraft from the 2^nd, 4^th, 5^th and 8^th Air Armies, compared to a German total of 175 aircraft.

'Braunschweig' (i) had twin objectives. The first was to spread confusion about the ultimate goals of the overall 'Blau' campaign. There was widespread feeling by almost all observers, especially Soviet high command, that the Germans would reopen their attack on Moscow during the current summer. By attacking in great strength toward Voronezh, near the site of the German forces' deepest penetration of the previous year, the Germans hoped to conceal the nature of the more important offensive taking place farther to the south. Soviet forces sent to the area of 'Braunschweig' (i) to shore up the defences would not be able to move with the same speed as the Germans, who would then turn to the south and leave them behind. The other objective was to provide an easily defended front line along the Volga river, providing a strong left flank that could be protected with relatively light forces, and also make it more difficult for the Soviets to use the river a a line of communication along which the armies farther to the south could be supplied.

The attack would be spearheaded by Hoth’s 4^th Panzerarmee. This highly mobile formation would move rapidly eastward to Voronezh and then turn to the south-east to follow the Don river to Stalingrad. As the 4^th Panzerarmee moved out of the captured city, the slower-moving infantry formations of Generaloberst Maximilian Reichsfreiherr von Weichs’s (from 15 July Generaloberst Hans von Salmuth’s) 2^nd Army following behind them would take up defensive positions along the river. The plan called for the 2^nd Army to arrive just as the 4^th Panzerarmee had cleared the city, and Hoth was under orders to avoid any street-to-street fighting that might bog down his army’s progress.

The city was defended by the troops of General Leytenant Markian M. Popov’s 40^th Army as part of the 'Valuiki-Rossosh Defensive Operation' (28 June/4 July 1942) of General Nikolai F. Vatutin’s South-West Front. Hoth’s powerful armoured forces moved forward with little delay, and the only natural barrier before the city was the Devitsa river, a tributary of the Don river running through Semiluki a short distance to the west. For reasons that are unclear, the bridge over the Devitsa was not destroyed, and Hoth’s forces were able to sweep aside the defensive forces placed there and reach the outskirts of Voronezh on 7 July. Soviet forces then mounted a successful counterattack that tied Hoth’s forces.

By 5 July, as forward elements of the 4^th Panzerarmee reached the Don river near Voronezh and became embroiled in the battle to capture the city, Stalin and the Soviet command still expected the main German thrust to be delivered in the north against Moscow, and thus believed that the Germans would turn to the north after taking Voronezh to threaten the Soviet capital. The Soviets therefore rushed reinforcements into the city to hold it at all costs, and also counterattacked the Germans' northern flank in an effort to cut off the German spearheads. General Major Aleksandr I. Lizyukov’s 5^th Tank Army managed to achieve some minor successes when it began its attack on 6 July, but had been driven back to its starting positions by 15 July after losing about half of its tanks.

As it reached Voronezh, the 4^th Panzerarmee should have been relieved by the infantry of the 2^nd Army, but this formation was still some distance from the city. Intense house-to-house fighting broke out, and Hoth continued to push some of his formations forward while he waited. At one point Generalmajor Helmuth Schlömer’a 3^rd Division (mot.) broke across the Don river but then turned back. The Soviet command poured reserves into the city and a situation not dissimilar from that which was to develop at Stalingrad a few months later broke out, with the German troops clearing the city street by street with flamethrowers while tanks provided fire support.

The 2^nd Army did not arrive for another two days, by which time the 4^th Panzerarmee was heavily engaged and took some time to extricate itself from the battle. The 2^nd Army continued the battle until 24 July, when the final Soviet forces to the west of the Don river were defeated and the fighting ended. Hitler later came to believe that these two days, when combined with other avoidable delays on the German drive to the south, provided Timoshenko with the time he needed to reinforce the Soviet forces in Stalingrad before the 4^th Panzerarmee could arrive to take this strategic target on the Volga river.

Although the battle for Voronezh was finally a German success, Hitler and von Bock argued over the next steps to be made in the operation. The combination of heated debate and continuing Soviet counterattacks, which tied down the 4^th Panzerarmee until 13 July, caused Hitler to lose his temper and dismiss von Bock. As part of the second phase of the operation, on 9 July, Heeresgruppe 'Süd' was divided into Heeresgruppe 'A' and Heeresgruppe 'B', with Generalfeldmarschall Wilhelm List appointed to command the former.

Only two weeks into the operation, on 11 July, the Germans began to suffer logistical difficulties and these slowed the advance. The 6^th Army was continually delayed by fuel shortages. Eight days later, on 20 July, fuel shortages were still hampering operations, leaving many formations and units unable to complete their assigned tasks. Generalleutnant Hans Freiherr von Boineburg-Lengsfeld’s (from 20 July for one month Generalmajor Erwin Mack’s) 23^rd Panzerdivision and Generalleutnant Bruno Ritter von Hauenschild’s 24^th Panzerdivision both became stranded during this opening phase. Once again, as it had done during the Norwegian campaign in April 1940 and 'Barbarossa' in 1941, the Luftwaffe’s Junkers Ju 52/3m force of three-engined transport aircraft delivered the most urgently required supplies in order to keep the army on the move. The situation remained difficult, with German troops forced to recover fuel from damaged or abandoned vehicles and, in some cases, to leave behind tanks and vehicles with heavy fuel consumption in order to continue the advance with more fuel-economical machines. This undermined unit strengths of many units, which were forced to leave behind many of their fighting vehicles. Nevertheless, the Luftwaffe flew in 200 tons of fuel per day to keep the army supplied. Despite this impressive performance in keeping the army on the move, Löhr was replaced by the more impetuous and offensive-minded von Richthofen.