The Germans were restless; "Greater Germany" was being restored, Austria and Czechoslovakia were theirs. They looked to the east – to the large expanses populated by nothing but "sub-humans," namely Poland.

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Germans Entering Paris, July 1940 photo courtesy of Yad Vashem

The German generals had fought in World War I, and had learned their lesson well. There were two things they wanted to avoid:

They did not want to get stuck in trench warfare.
World War I, with its trenches, bombs and gas being thrown back and forth, had cost a lot of money and casualties with very little progress.

The solution was the "Blitzkrieg,"the "lightning-strike" – mobile tanks and cannons and troops, all designed to break through static defenses.

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German Planes Attacking Athens, Greece photo courtesy of Yad Vashem

They did not want to get stuck in a two-front war. In World War I, the Germans were fighting the Russians on the one side, and the Allies on the other.

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Signing Russian/German Non-Aggression Pact photo courtesy of Yad Vashem

So, after years and years of Hitler’s ranting and raving that he was going to strike at Communism, he suddenly became good friends with Stalin. They signed a "non-aggression" pact. (Note that Stalin’s foreign minister was a Jew, but Stalin knew that Hitler would never sit down and sign a treaty with a Jew, so he replaced him.)