This is a difficult question because it really unclear as to whether the allies would have beaten Germany. The war definitely would have gone on for a longer time period and the United states may have also dropped the atomic bomb on Germany. Germany really messed up by attempting to invade Russia. Even though Hitler studied Napoleon lll who fatally invaded Russia and lost he still made the decision to invade. Hitlers soldiers were totally unprepared for the Russian winter and had little supplies which led to the deaths of hundreds of thousands of German troops. If Hitler had decided not to invade Russia and fight a two front war, it is very possible that the allies would have lost or won by a smaller margin.
