Nonetheless, the power of the enemy attack and the speed of the Rumanian collapse took the Germans by surprise. Even at this stage of the war, they seem to have underestimated the striking power of the Soviets, not least since they knew that the Stavka, too, had pulled units from the Second and Third Ukrainian Fronts in order to feed the demands of the larger operation to the north. In addition, although the Red Army in this sector disposed of large numbers of troops, a sizable percentage of them had little or no training. These men, primarily Ukrainians who had been swept up to make good manpower losses as the Red Army liberated Ukraine, filled out the ranks, although German analysts were convinced that Soviet infantry divisions did not have quite the striking power as before. This was likely true, but the Red Army made up for this deficiency by relying more on artillery, tanks, and air support, to devastating effect once the attack had begun. Typically, the Russians amassed a huge force of over 1.3 million men with almost nineteen hundred tanks and assault guns for the offensive. As in Belorussia, the Soviets planned to concentrate their forces at key points in order to achieve an operational breakthrough. The original intention seemed to be just to force the Germans to divert troops away from the central front, thus opening the Warsaw-Berlin axis to further attack. Ultimately, however, the Soviets devised an ambitious new plan that aimed to encircle and destroy enemy forces around Iassy and Kishinev, then advance deep into Rumania to seize Bucharest and the Ploesti oil fields.47
The attack began on 20 August, but, despite the fall of Iassy the next day and Kishinev on the twenty-fourth, it did not initially proceed as smoothly as the Russians had hoped. While, in many areas, Rumanian troops put up little opposition, German units resisted stoutly. Not atypically in Rumanian history, politics played a key role in determining the outcome of the battle. Prompted by the attack, opposition leaders in Bucharest, who had been seeking a way out of the war for months, launched a coup against the pro-German government of Antonescu on 23 August. Troops loyal to the new government under the young King Michael, who had promptly taken Rumania out of the war, then successfully prevented a German countercoup. This incited Hitler, who had evidently counted too heavily on the anticommunism of Rumanian politicians and, thus, was taken completely by surprise by the political turn of affairs, to order the bombing of Bucharest, an action that only motivated the Rumanians to enter the war on Russia’s side (which allowed them the additional benefit of fighting the hated Hungarians as well as recovering Transylvania). Within a few days, Rumanian troops in some sectors thus went from working alongside the Germans to fighting against them. Although German troops responded to the unexpected collapse of their ally with their usual skill and tenacity, by early September Army Group South Ukraine had suffered a fate similar to that of Army Group Center: the Sixth Army had been destroyed (again), the German front in Rumania had completely collapsed, and both Bucharest and the Ploesti oil fields had been lost. Although earlier in the war the loss of the latter would have occasioned German economic collapse, by this stage it proved largely meaningless. Persistent American bombing raids over Ploesti had virtually ended production at its refineries even before the Russians arrived, while the Germans had long since turned to synthetic production to supply most of their fuel needs. Still, at a relatively small cost of 67,000 casualties, the Red Army had again shattered an entire front, destroyed twenty German divisions, and inflicted a loss of more than 200,000 soldiers on the Germans. The renamed Army Group South, with only some 200,000 men left, now embarked on a lengthy retreat across the Carpathians that did not stop until Soviet forces had penetrated Bulgaria and turned west into Hungary.48
As the Soviet advance continued into Hungary, however, it ran into more problems from logistics than from German opposition. By the end of September, Russian forces had swept aside the rather light German and Hungarian forces covering the Carpathian passes and had passed into Hungary. The Stavka now directed that German and Hungarian forces be destroyed and Hungary knocked from the war, but this was to prove much more difficult than anticipated. With the loss of the Ploesti oil fields and refineries as well as the extensive damage done by American bombers to the synthetic fuel plants, Hitler put great store in the oil fields southwest of Lake Balaton as well as those on the Hungarian-Austrian border. Still, with German defenses in Hungary rather thin, the Soviets advanced rapidly, seizing Debrecen, about 120 miles east of Budapest, on 20 October. There they stalled, brought to a halt by a concerted German counterattack. The Soviets now tested the Hungarian defenses to the south of Budapest, taking Szeged, little more than a hundred miles southeast of the capital, on 10 November. Once again, however, stiff German resistance, as well as bad weather, stopped the Russian advance. The Red Army kept up steady pressure, however, and by 3 December had reached the shores of Lake Balaton, no more than forty miles southwest of Budapest. The Soviets tried again in a two-pronged attack on 5 December to seize the city, but, despite a successful opening advance, the Germans shifted forces and prevented the capital either from falling or from being encircled.49
Having ousted Admiral Horthy, the aged Hungarian leader, from power following his unsuccessful attempt in mid-October to take Hungary out of the war, Hitler was more determined than ever to hold on to Budapest. In early December, he dispatched two panzer divisions and three sixty-tank Tiger battalions for a counterattack. The question, however, was, Where? In the north or in the south? General Friessner, over-matched and destined along with Busch to become the least successful of German eastern front commanders, saw the greatest danger in the south, while Guderian believed that the main danger lurked in the north. In the end, Hitler approved Friessner’s dispositions, with the result that the infantry from the panzer divisions was deployed in the north while the unsupported armor was left to defend the line in the south. These odd deployments meant that, if the Soviets beat the Germans to the punch, the latter were in serious trouble. Bad weather and a bout of caution caused the Russians to delay their assault, but, despite repeated urging from Guderian, Friessner hesitated to attack before the ground froze. As a consequence, much as Guderian had feared, the Soviets struck first, launching a massive two-pronged assault both north and south of Budapest on 20 December. By the twenty-seventh, they had encircled the city, but Hitler was determined to hold the Hungarian capital since, in his mind, success in the Ardennes and success in Hungary were linked. In addition, since it lay athwart the main route to Austria and Bohemia and was the main rail hub in the region, the Russians could not simply bypass it, so, for the first time in the war, the Soviets found themselves laying siege to a major city. Budapest, with its civilian population swollen to 2 million, was to be assaulted in savage air and artillery bombardments to force its surrender.50