In Order No. 45, Hitler ordered his armed forces to occupy the Caucasus and Stalingrad in the summer of 1942. The offensive began in July. Against the advice of his generals, Hitler split up his forces and attempted to occupy both areas concurrently. In September, Stalin again summoned Field Marshal Georgi Zhukov, posted him to the Stalingrad front, and assigned General Vasily Chuikov to defend the city itself. The battle for Stalingrad escalated on August 26 as a 1-million-strong German force attacked the defending Russian forces. The population’s morale was poor; in one aerial attack alone, 600 aircraft claimed 40,000 casualties. Despite the Soviet soldiers’ display of supreme valor, the German supremacy in material forced the defenders to retreat gradually into the city proper. On September 13, a German division broke through the town’s defense lines and nearly reached Chuikov’s headquarters in house-to-house, floor-to-floor, and room-to-room fighting. Parts of Stalingrad were occupied and reduced to mounds of soil. Soviet units fought to the last soldier. Chuikov had every building mined and posted snipers at every spot.