A typical unit of Soviet infantry in Smolensk, July 1, 1941. Note their assortment of weapons from Mosin-Nagant Rifles to PPSh-41s.
This all changed on 22 June 1941 with the launch of Operation Barbarossa – Hitler’s invasion of the Soviet Union. German forces penetrated deeply into Soviet territory, destroying of surrounding hundreds of thousands of Russian troops and decimating entire army divisions, in a series of major battles at Smolensk, Odessa and Kiev amongst others. Stalin’s forces – weakened by the Great Purge where thousands of Soviet officers had been imprisoned or executed – struggled to contain the German advances.
As a result, the Soviets were pushed further and further back, the major Russian port city of Leningrad surrounded and besieged and the capital itself, Moscow seriously threatened by advancing German forces.
Operation Barbarossa: The German Invasion Of Russia, 22 June — 25 August 1941.
However, the German attacks had inflicted enormous casualties on the Russians and swallowed up vast tracts of territory, but Hitler had not anticipated the Soviet Union continuing to resist. Hitler’s soldiers were not prepared for the Russian winter, no long-term strategic planning was in place and the supply infrastructure was inadequate for a lengthy conflict.
Despite the initial early, rapid successes, Operation Barbarossa ground to a halt towards the end of the year on 5th December, on the outskirts of Moscow just nine miles from Red Square. Temperatures were rapidly dropping; vehicles were starting to freeze over and soldiers increasingly suffering from frostbite.