'Dampfhammer' was the German alternative designation for 'Blau III', the third-phase southward extension of the German 1942 summer offensive on the Eastern Front into the Caucasus, and the codename under which the operation was launched (9 July/18 November 1942).
'Blau' was the great three-phase German summer offensive whose first phase in the north was 'Blau I', otherwise known as 'Braunschweig' (i), launched on 28 June, second phase in the centre 'Blau II', otherwise 'Clausewitz' launched on 30 June, and third phase in the south 'Blau III', otherwise 'Dampfhammer' launched on 9 July.
The operation was initially named 'Blau', which is generally used to label the entire three-part undertaking, but this was changed to 'Braunschweig' (i) on 30 June, though this latter name is generally applied only to the first phase.
Hitler had personally intervened in the plans for this operation, and had also ordered the division of Generalfeldmarschall Fedor von Bock’s Heeresgruppe 'Süd'. This caused considerable alarm in the all branches of the German general staff, and especially in the Oberkommando des Heeres responsible for operations on the Eastern Front, and on several occasions senior officers warned Hitler about the dangers inherent in this division. Later studies confirmed this split to be one of the main causes for the eventual demise of the 6th Army in Stalingrad.
Hitler persisted in this division of Heeresgruppe 'Süd' for strategic reasons, namely the divergent axes required for the German seizure of the oilfields of the Caucasus region and the severance of Soviet supply route along the Volga river through Stalingrad. On 23 July Hitler further elaborated his thinking in Führerweisung Nr 45 to ordain that Generalfeldmarschall Wilhelm List’s new Heeresgruppe 'A' (the southern element of what had been Heeresgruppe 'Süd') was to take the Caucasus region and Baku in 'Edelweiss' (i) ('alpine violet' as the offensive involved the seizure of the alpine terrain of the Caucasus mountain range) as an extension of 'Dampfhammer', and that Generalfeldmarschall Maximilian Reichsfreiherr von Weichs’s new Heeresgruppe 'B' (the northern element of what had been Heeresgruppe 'Süd') was to take Stalingrad and, if possible, Astrakhan at the debouchment of the Volga river into the Caspian Sea in the 'Fischreiher' ('heron' because of the fish in the Volga river) extension of 'Clausewitz'.
At the northern end of the Eastern Front, Generalfeldmarschall Wilhelm Ritter von Leeb’s Heeresgruppe 'Nord' was to conquer Leningrad in 'Feuerzauber' ('fireworks' because of the volume of artillery fire which was to be used).
In his Führerweisung Nr 45, Hitler said that 'In a campaign of little more than three weeks, the ultimate goal I set the south wing of the Eastern Front have already been accomplished. Only some rather weak enemy forces belonging to the armies of Timoshenko have managed to escape the envelopment and reach the bank of the Southern Don. 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.'
The 'Dampfhammer' operation was thus designed to take Generalfeldmarschall Erich von Manstein’s 11th Army and Generaloberst Richard Ruoff’s 17th Army plus Generaloberst Ewald von Kleist’s 1st Panzerarmee of Generalfeldmarschall Wilhelm List’s new Heeresgruppe 'A' from eastern Crimea (11th Army) and the line of the Don river (17th Army and 1st Panzerarmee) into the Caucasus with the object of taking the oilfields at Maykop, Grozny and Baku, as well as Sukhumi and Batumi on the Black Sea coast.
The offensive ultimately failed as a result of the radical overextension of German lines of communication and the sterling defence of Marshal Sovetskogo Soyuza Semyon M. Budyonny’s North Caucasus Front and General Ivan V. Tyulenev’s Trans-Caucasus Front, which had halted the Germans along the line of the Terek river by 18 November 1942.
The offensive also had the shorter-term consequence of persuading Hitler, on 17 July, to divert part of Generaloberst Hermann Hoth’s 4th Panzerarmee from the drive on Stalingrad to support Heeresgruppe 'A'. This reinforcement did not produce the desired result, and the diversion also helped to condemn Generaloberst (later Generalfeldmarschall) Friedrich Paulus’s 6th Army to its strategically decisive defeat at Stalingrad during the following winter.