Under Operation Barbarossa, Field Marshal von Bock’s Army Group Centre had a target of Moscow. On 2 October 1941, Operation Typhoon – the Battle of Moscow – began with one million men, 1,700 tanks, 19,500 artillery guns and 750 combat aircraft at von Bock’s disposal. They began in favourable weather and successfully encircled the nine armies of the Red Army at Vyazma and Bryansk, but were then slowed by both the captured troops and extremely muddy conditions. The delay strengthened the Soviets, but the Germans were still able to break through the Mozhaisk Line before stalemate hit. The Soviets, under Marshal Zhukov, conjured more troops, artillery and tanks, created fortress-type defences around Moscow and organized resistance groups. On 15 November, the Germans launched a second, targeted and concentrated attack, yet the Russian line of defence held and the freezing temperatures halted the German offensive. Soviet counterattacks on 5 and 6 December pushed Army Group Centre back from Moscow. Their strategic retreat was against Hitler’s wishes and von Bock was sacked.