I assume you're referring to 1941, Operation Barbarossa?

The reason why Hitler kept pushing was to capture Moscow. Despite the winter coming, they were so close, so confident in victory that they just couldn't stop. Here's a timeline of the events.

• September 26 1941 “Operation Typhoon” – the German offensive for the capture of Moscow is ordered.

• October 2 1941 The offensive to capture Moscow begins in ideal weather conditions

• October 7 1941 Panzer spearheads seal off the Soviet forces in the Vyazma and Bryansk pockets.

• October 8 1941 Heavy rains set in. The “mud season” begins to strangle the German mobile units, except for tanks.

• October 19 1941 Stalin proclaims a state of siege in Moscow.

• October 20 – 25 1941 Stiffening Soviet resistance and struggling supply lines halt the original “Typhoon” offensive. New orders are issued for advances on more limited objectives to safeguard the German front line.

• November 15 1941 After initial success, the second phase of the Moscow offensive is paralysed by 20 degree of frost and ever –strengthening Soviet forces.

• November 27 1941 Panzer spearheads struggle to within 19 miles of the northern outskirts of Moscow, but are halted by fierce counter-attacks. South of Moscow, the advance German units reach Kashira, but are also halted.

• December 5 1941 After obstinate argument, Hitler agrees to abandon the Moscow offensive for the winter. Army Group Centre begins to retreat to safer defensive positions.