The Soviet forces were apparently unprepared despite numerous warnings from a variety of sources . They suffered much damage in the field because of mediocre officers , partial mobilization , and an incomplete reorganization . The hasty pre-war forces expansion and the over-promotion of inexperienced officers ( owing to the purging of experienced officers ) favored the Wehrmacht in combat . The Axis 's numeric superiority rendered the combatants ' divisional strength approximately equal . A generation of Soviet commanders ( notably Georgy Zhukov ) learned from the defeats , and Soviet victories in the Battle of Moscow , at Stalingrad , Kursk and later in Operation Bagration proved decisive
purging
Great Purge
Red Army