I hope this question refers to the battle of stalingrad
This was a major turning point in WW2 as the Red guard strategically frustrated Hitler delaying his lightening victory tactics, until his soldiers were starved off food, supplies and weakened by encroaching winter. the heavy military loss that Hitler suffered at Stalingrad was never recoverable and from that point forward Hitler was fighting a defensive war from two fronts, a fete that heavily suffocated him.