🔶Tag a Friend!🔶This picture shows a German soldier on top of a statue of Lenin.
Just by looking at this picture you can tell that, even though this was meant to be comical, there was real strife between the German and Soviet regimes. They did not agree on anything except agreeing to disagree.
But Hitler knew in 1939 that if war should brake out, which was very possible, Germany could not afford to fight on two fronts like they did in WW1.
The solution was the Molotov-Ribbentrop Pact, which was signed August 23rd of 1939, just 7 days before the Germans crossed the border into Poland.
This non-aggression pact set in stone not only Germany's early victories, but the fate of Poland, Denmark, Norway, France, the Low Countries, Yugoslavia, and Greece. I say this because had the USSR gone against Germany at the outbreak of war, it's likely the combined efforts of the Poles, French, British, and the Soviet Union would have been enough to stifle and halt the German blitzkrieg. (Hypothetical)
In reality, Joseph Stalin knew his military was in shambles after the purges he committed against it, and that a pact with Germany was the best way to protect his regimes interests.
The pact also made a deal cutting Poland into two sectors of occupation; one Soviet and one German.
After Germany had almost completely wiped out all of Europe minus the Iberian Peninsula (Neutral), the U.K., Sweden (Neutral), Switzerland (Neutral), Finland (not a German target and later would be their ally), and of course the USSR, Hitler's ego and overconfidence got the best of him when he decided to invade the USSR, breaking the non-aggression pact with Stalin.
It had always been part of Hitler's agenda to invade the USSR as he could not see his Reich living side by side to a regime such as the Soviets. This is found in Mein Kampf.
But, his decision to invade so early, while not completely unfeasible to understand, was not the best move, as we know. He should have waited until Britain either surrendered or was conquered because with them still above water, the possibility of a second front (and third front in North Africa which already had become the second front) was still very real.