On 31 January 1943, the 90,000 survivors of the 300,000-man 6th Army surrendered. By that time the Hungarian 2nd Army had also been wiped out. The Red Army advanced from the Don to the west of Stalingrad, marching through Kursk (retaken on 8 February 1943) and Kharkov (retaken 16 February 1943). To save the position in the south, the Germans decided to abandon the Rzhev salient in February, freeing enough troops to make a successful riposte in eastern Ukraine. Manstein's counteroffensive, strengthened by a specially trained SS Panzer Corps equipped with Tiger tanks, opened on 20 February 1943 and fought its way from Poltava back into Kharkov in the third week of March, when the spring thaw intervened. This left a glaring Soviet bulge (salient) in the front centered on Kursk.