On 5 July 1943, Model led the northern assault on Kursk during Operation Citadel, a plan which had caused great controversy within the German high command. Günther von Kluge and Erich von Manstein, commanding Army Groups Centre and South respectively, had originally urged that the salient be attacked in May, before the Soviets could prepare their defences. Others, including Heinz Guderian, felt that attacking was unnecessary, since it would occasion heavy tank losses and thus upset plans for increasing German armored strength. Model was also skeptical of the plan's chances, pointing out that Konstantin Rokossovsky's Central Front was strongly dug in and outnumbered him two to one in men, tanks and artillery. Rather than conclude that the offensive be called off, however, he said it should be postponed until he could receive further reinforcements, in particular the new Panther tanks and Ferdinand tank destroyers.