The Battle of Barbarossa

The Russians were able to beat Germany only at the expense of oceans of blood. They threw incredible amounts of man, human lives into the meat grinder. So most of the fighting was done by the Russians but the Americans take it because of Hollywood and propaganda. And because of a tactical or strategic mistake, that's why they eventually lost. The operation in Barbarossa eventually became a disaster because of a strategic mistake. They went for the south instead of going straight for Moscow. Eventually the tide turned.