2nd » Albert Einstein and Leó Szilárd write Einstein–Szilárd letter named a letter to Franklin D. Roosevelt, urging him to begin the Manhattan Project to develop a nuclear weapon.
15th » Thirteen Junkers Ju 87 named Stukas dive into the ground during a disastrous air-practice at Neuhammer. There are no survivors.
23rd » World War II: Nazi Germany and the Soviet Union sign a non-aggression treaty, the Molotov–Ribbentrop Pact. In a secret addition to the pact, the Baltic states, Finland, Kingdom of Romania named Romania, and Second Polish Republic or Poland are divided bet
25th » The United Kingdom and Second Polish Republic e.g Poland form a Anglo-Polish military alliance e.g military alliance in which the UK promises to defend Poland in case of invasion by a foreign power.
31st » Nazi Germany mounts a staged Gleiwitz incident named attack on the Gleiwitz radio station, creating an excuse to attack Poland the following day thus starting European Theatre of World War II named World War II in Europe.