The 'Graz-Amstetten Offensive Operation' was a Soviet undertaking by Marshal Sovetskogo Soyuza Rodion Ya. Malinovsky’s 3rd Ukrainian Front in Austria (15 April/9 May 1945).
In the course of the 'Vienna Strategic Offensive Operation' between 16 March and 15 April 1945, the Soviet forces of the 2nd Ukrainian Front and 3rd Ukrainian front inflicted a severe defeat and heavy losses on Generaloberst Dr Lothar Rendulic’s Heeresgruppe 'Süd'. Even as the 'Vienna Strategic Offensive Operation' was under way, on 1 April the Soviet supreme command ordered the left flank of the 3rd Ukrainian Front, comprising the 26th Army, 27th Army, 57th Army and Bulgarian 1st Army, be detached to undertake the seizure of the Austrian cities of Gloggnitz, Bruch and Graz by 10/12 April, and also the Yugoslav city of Maribor, as well as gaining a form foothold on the Mürz, Mur and Drava rivers. By the end of the 'Vienna Strategic Offensive Operation', however, the Soviet forces had not been able to fulfil these tasks fully.
On 13 April, therefore, the Soviet supreme command clarified the front’s current tasking: the front’s right-wing forces were to reach the Traisen river and take St Pölten, while the front’s central and left-wing forces were to go over to the defensive and start active actions only if the right-wing offensive proved successful. Following this instruction, on 15 April the 3rd Ukrainian Front, without any operational pause, continued its offensive in the general direction of Graz. The task was to complete the destruction of Heeresgruppe 'Süd' and advance to the agreed line of contact with the US forces which were soon to enter the western part of Austria from the west and south-west.
For the new offensive the 3rd Ukrainian Front had 294,760 men, and comprised General Leytenant Nikanor D. Zakhvatayev’s 4th Guards Army, General Polkovnik Vasili V. Glagolev’s 9th Guards Army, General Leytenant Nikolai A. Gagen’s 26th Army, General Polkovnik Sergei G. Trofimenko’s 27th Army, General Polkovnik Mikhail N. Sharokhin’s 57th Army, General Polkovnik Vladimir A. Sudets’s 17th Air Army, General Leytenant Ivan N. Russiyanov’s I Guards Mechanised Corps, one tank corps, General Leytenant Sergei I. Gorshkov’s V Guards Cavalry Corps and General Leytenant Vladimir D. Stoychev’s Bulgarian 1st Army. The combined-arms formations totalled 42 infantry divisions and four airborne divisions. The offensive was carried out without any operational pause, so troop, weapons and equipment replenishment before the start of the operation was not possible, and as a result there soon emerged major shortages, especially of men.
By the start of the Soviet offensive, Generaloberst Dr Lothar Rendulic’s Heeresgruppe 'Süd', which was redesignated as Heeresgruppe 'Ostmark' on 30 April, had been offered not the slightest opportunity to recover from its heavy defeat in the 'Vienna Strategic Offensive Operation', and currently totalled some 450,000 men. Operating against the 3rd Ukrainian Front were General Hermann Balck’s 6th Army and SS-Oberstgruppenführer und Generaloberst der Waffen-SS Joseph Dietrich’s 6th SS Panzerarmee. To the south, in the area of the Yugoslav/Austrian border, was General Maximilian de Angelis’s 2nd Panzerarmee. The German armies included Hungarian as well as German divisions.
Given the strategic and operational conditions prevalent as the start of the 'Graz-Amstetten Offensive Operation', with its forces in an accelerating state of collapse on every sector of the Eastern Front, the German high command could consider nothing more tan an attempt to slow the Soviet offensive and thereby create a situation in which its surviving forces could undertake an orderly retreat to the west for surrender to the Western Allies rather than the USSR.
The 'Graz-Amstetten Offensive Operation' was in fact started by a powerful pre-emptive counterattack by the 6th SS Panzerarmee on the 3rd Ukrainian Front’s right flank. Between 15 and 29 April, the 9th Guards Army and 26th Army repulsed the attacks of the 6th SS Panzerarmee, while slowly moving forward through the operational area’s mountainous and wooded terrain, in which the German managed on occasion to drive back the advancing Soviet troops, especially those of the 26th Army, as there arrived new units from Yugoslavia and even from Italy. In essence, therefore, the Soviet offensive was not the planned deep offensive drive but rather an amorphous clash between opposing forces on every size.
On 29 April, the 3rd Ukrainian Front launched a major offensive westward in the eastern parts of the Alps. In the last days of April, elements of the 4th Guards Army advanced towards Melk and reached the Pylah river, and then in the direction of Loosdorf and Amstetten. On 5 May, the 9th Guards Army, which had born the brunt of the offensive up to this time, was transferred to the 2nd Ukrainian Front for commitment in the 'Prague Strategic Offensive Operation'. On 7 May, the Soviets established that the German forces were pulling back under cover of strong rearguards.
On 8 May, all the 3rd Ukrainian Front’s armies launched a general offensive, advancing between 10.5 and 46.5 miles (17 and 75 km) in a day. On the same day, Soviet troops stormed into Amstetten and occupied Melk, Mautern, Graz and five other cities as well as more than 100 smaller towns and villages. At 15.00 on 8 May, in the area of the Ens river in southern Bavaria, Soviet and US forces met.
On 9 May, the Soviet pursuit of the fleeing German troops continued, and Bruch, Leoben, Maribor and six other cities were taken. Throughout this day, as on earlier days, the Soviet air units continued to bomb and strafe the German troops retreating toward Ens.
From the beginning of the operation, the 57th Army had been on the defensive, and only on 8 May did it go over to the offensive toward Feldbach and Graz. By the end of the day, the VI Guards Corps had neared Feldbach, and although the Germany had signed an unconditional surrender on 9 May, Feldbach was taken by storm on that day after its garrison had refused to surrender.
Later, and despite Germany’s unconditional surrender, fierce fighting continued in Austria. Thus on 10 May, the 26th Army led the assault on Judenburg, whose garrison refused to surrender. By 11 May, Soviet forces had interdicted the main routes along which the German forces were still attempting to withdraw into the eastern part of the Alps, forcing them to surrender in large numbers. Between 9 and 12 May, about 126,000 Germans surrendered to the 3rd Ukrainian Front.
Even so, the fighting was still not over. There were pockets of German resistance throughout Austria, and defeated German troops constantly tried to break through into the US zone of occupation. During 13 May, for instance, 2,945 German soldiers were taken prisoner, and 14 May another 419 men. On 15 May, a large group of German soldiers was intercepted and forced to surrender as it attempted to break through from Yugoslavia to the US zone of occupation, some 27,754 men being taken prisoner: these were 15,300 Croats of the Ustase movement and 10,530 Germans. Operating on the southern flank of the front, the Bulgarian 1st Army between 13 and 17 May captured more than 30,000 Ustase and later handed these over to the Yugoslavs. In the days which followed, combing of the area continued and many other scattered groups and individual soldiers were captured: on 19 May, for example, 65 Hungarian soldiers were captured, on 21 May 98 German soldiers and on 24 May several dozen Hungarian soldiers.
In general, at the end of April and beginning of May, the 3rd Ukrainian Front was established along the line from Linz to Klagenfurt via Gaflenz, with US forces on the other side of this line. The attempted withdrawal of Generaloberst Alexander Löhr’s Heeresgruppe 'E' from Yugoslavia had been thwarted, as as a result it had been engaged and largely defeated by Yugoslav forces. In the conditions of the almost complete liberation of Austria from German troops, on 27 April a provisional government was created in Austria.
During the 'Graz-Amstetten Offensive Operation', the 3rd Ukrainian Front had lost 2,173 men killed or missing and 6,552 men wounded or taken ill.
German data on their own losses have not been established with any precision as the maintenance of documentation and reporting as this sector of the Eastern Front collapsed ceased for all practical purposes. Soviet data on German losses claim that between 15 April and 8 May that the men of the 3rd Ukrainian Front killed 39,490 German and Hungarian and took prisoner 9,226 me. On 9 May, 10,830 more Germans and Hungarians were taken prisoner by the 26th Army and 57th Army.