When World War II began, Nazi Germany had an unimaginable advantage of surprise. The Nazis had prepared for the war for years while the Allied countries had no idea what was going on.
Adolf Hitler would never have begun a military campaign if it was doomed to fail and boomerang. Germany held four aces when the war began, but the costly decisions Hitler made along the way saw the German advantages metamorphose into disadvantages. The Nazis could have won the war if they had made these decisions differently.