The fact that Hitler’s Germany had to fight a two-front war -- in the west, against the U.S., the U.K. and other allies, and in the east against Russia -- played a critical role in that country’s defeat, and without it, the course of the war may have been different. In short, the Germans could not sustain assaults from the U.S., U.K. and their allies in the west and the Soviet Union -- the predecessor to Russia -- in the east after D-Day.

The Hitler-Stalin Pact

In 1939, German Chancellor Adolf Hitler and Joseph Stalin, premier of what was then the Soviet Union, signed a non-aggression pact. In essence it declared that they wouldn’t make war on each other even though the two dictators had different ideologies and Hitler disliked Stalin. At that point, Hitler had already taken Czechoslovakia and was looking to invade Poland, and he calculated that the only power able to effectively stop him was the Soviet Union. But Hitler never meant for the deal to be permanent -- the Nazis wanted to destroy communists along with the Jews --and Hitler believed that to defeat the Soviets would quickly mean an end to the war in Europe. In December 1940, Hitler signed Directive 21, which ordered the invasion of the Soviet Union. The invasion began the following June.

Germany Attacks

On June 22, 1941, more than 3 million German troops -- along with soldiers from Finland, Romania and later Italy and other German allies -- invaded the Soviet Union, kicking off the largest military battle in history. The Soviets were caught off-guard. Germany made rapid advancements in the first few weeks, and Hitler expected the Soviet Union to crumble. But it did not. And as the brutal winter took hold, the Soviets counterattacked, driving the Germans from Moscow. The following winter, Germany would suffer a catastrophic defeat at Stalingrad, after which the Soviets began pushing the Germans out of their country. By the summer of 1944, a Soviet invasion of Germany looked likely.

D-Day

On June 6, 1944, the Allied forces -- including the U.S., United Kingdom, France and the Soviet Union -- began a campaign to take back Western Europe from the Germans, in what is now called the D-Day invasion. This meant the Germans were effectively boxed in, battling the world’s greatest economic powers -- the Soviets from the east and now the other Allies from the west. Germany did not have the resources or the personnel to withstand the assaults.

The End

It was the Soviets, and not the Allied troops under Gen. Dwight Eisenhower, who took the German Reichstag in April 1945. With both forces converging on Berlin, Hitler took his own life. Historians would later point to numerous tactical errors that Hitler made during the war; chief among these were the decision to declare war on America after the Japanese bombed Pearl Harbor in 1941, thus ensuring America’s entry into the Western Front and the invasion of the Soviet Union. As had happened in World War I, German troops were too boxed in and spread too thin by the two-front war to emerge victorious.