if you look at the russian front most of the major defeats on Germany were inflicted in the east…
battle of moscow, stalingrad, kursk…
People say that USSR would have declared war on germany had Hitler not backstabbed first, but you have to remember that the USSR wasnt exactly best pals with the US and UK…after all during the russian civil war the US and UK sent troops to fight against the bolsheviks.
also the reason that the Battle of Britain was one was because of germany withdrawing air power from France to the east (balkans and Russia)…had this not happened i think Britain would have been knocked out around early 1942, or maybe earlier then that.
with Britain gone it would be very hard for the US to attack trans-atlantic against a well defended europe.
also it was the Germans who declared war on the USA after pearl harbour not the other way round. USA might never have come into the european war.
oh btw just reading other posts on ‘could germany have broken USSR’ i think they could have easily…the invasion was meant to be in may but it was put back due to invasion of balkans…this meant that the german army was stopped before moscow (20miles) by the perma-frost…which had they invaded on time would not have been there. Germany made terible blunders…the fact that they went for a set-piece battle at stalingrad was dumb, as was the 1942 offensive on causasus oil fields in general. At kursk yet again due to massive delays to the attack the russians were able to prepare many defenses to stop it…which is what happened.
i think the soviet victory was more thanks to German blunders between summer 1942 and summer 1943.