After the controversial "Kassa attack", elements of the Royal Hungarian Army joined the German invasion of the Soviet Union, Operation Barbarossa, one week later than the start of the operation. In spite of the arguments made that Hungary (unlike Romania) had no territorial claims in the Soviet Union, the fateful decision was made to join the war in the East. In the late summer of 1941, the Hungarian "Rapid Corps" ("Gyorshadtest"), alongside German and Romanian army groups, scored a huge success against the Soviets at the Battle of Uman. A little more than a year later and contrasting sharply with the success at Uman, was the near total devastation of the Hungarian Second Army on banks of the Don River in December 1942 during the Battle for Stalingrad.