Agreed with the above post. Hitler made a grave mistake by invading the Soviet Union, which outnumbered him three to one in population, and had massive distances and areas to contend with. It's unconquerable without nuclear weapons, much as the US is. By staging the attack, it guaranteed that he would lose the war.
It was also one of the most destructive, brutal and bloody wars in human history. 20 million Soviets died and 3 million Germans were killed. Entire cities and states were laid waste. There were massive refugee populations, 1.5 million Jews were murdered and thousands of war crimes were committed by both sides in the war. Stalin refused to trade for his POWs (including one of his own sons), and refused to give back any German POWs. Most of them died in Soviet labor camps.