Ribbentrop-Molotov: the aggression pact that started WW2.
On August 23, 1939, Soviet Russia and Nazi Germany signed the Molotov - Ribbentrop pact, named after the Soviet foreign minister Vyacheslav Molotov and the Nazi German foreign minister Joachim von Ribbentrop. The biggest historical misconceptions regarding the Molotov - Ribbentrop pact is that it was a "non aggression" pact while in fact it was the exact opposite. In reality it was in fact an "aggression" pact which made Soviet Russia and Nazi Germany allies, and enabled Hitler and Stalin to invade Poland and start WW2, and also enabled Stalin to invade Finland and occupy the Baltic states - Estonia, Latvia and Lithuania and parts of Romania (Bessarabia).
Officially the pact was a non aggression pact between Soviet Russia and Nazi Germany, but a secret protocol hidden from the world told the real story of this pact
Joachim von Ribbentrop, Stalin and Vyacheslav Molotov after signing the pact.
The secret protocol divided the territories of Romania, Poland, Lithuania, Latvia, Estonia, and Finland into German and Russian "spheres of influence" basically carving out future central and eastern Europe between Russia and Germany. The pact also extended to the economic sphere, with Germany providing military equipment in exchange for Russian raw materials such as oil, grain, iron and phosphates. The Molotov - Ribbentrop pact also cleared the last obstacle in Hitler's path to invade Poland, the event that caused WW2. It also showed how the allegedly opposite ideologies of Nazism and Communism, had no problem to work together in harmony and that the real difference between them were only in the realm of semantics and economic theories.
Hitler's main worry regarding the invasion of Poland, which refused any sort of alliances with Nazi Germany or Soviet Russia, was how would Stalin react. Hitler realized that Poland's allies, France and the UK, would not honor their defensive treaties with Poland and attack him if he were to invade Poland, but he was not sure of how Stalin and Soviet Russia will react. After the pact was signed, Hitler knew that he could count on his new ally Stalin not only not to interfere, but to actively help him and support him in his invasion of Poland.
Nazi and Soviet officers greet each other in occupied Poland in 1939.
For Hitler, the pact provided a guarantee that he could invade first Poland, then France and the rest of western Europe later, at his liesure, without having to worry about any threat from the east. For Stalin, it allowed a breathing space in which to build up armed forces that had been severely damaged by the purges of the previous years, as his botched invasion of Finland in 1939 showed (the Winter war). It also gave Stalin the chance to expand the Soviet Union to include parts of the old Russian empire of pre-revolutionary times which included the Baltic states and also parts of Finland and Romania.
Just over a week later after signing the pact, Hitler invaded Poland, and 17 days later the Red Army invaded Poland from the east. The Molotov - Ribbentrop pact, which made Germany and Russia allies untill Germany invaded Russia in 1941, was the main reason for the outbreak of WW2 in Europe, and anyone who views it as a "non aggression pact" is either deluded, brainwashed or just plain ignorant when it comes to WW2 history. In recent years there has been a concentrated propaganda campaign by Russia and Vladimir Putin to rewrite the history around the The Molotov - Ribbentrop pact and remove the historical fact of how Stalin and the USSR helped Nazi Germany start WW2 and how they were basically allies until 1941. Putin has even gone as far as blaming Poland for being responsible for starting WW2 and the fact that it was invaded by Nazi Germany in 1939m and not Stalin and the USSR.
Bibliography: "Origins of the second world war", AJP Taylor. "Bloodlands", Timothy Snyder.