 At first, Hitler rebuffed Soviet diplomatic hints that Stalin desired a treaty; but in early August 1939, Hitler authorised Foreign Minister Joachim von Ribbentrop to begin serious negotiations. A trade agreement was concluded on 18 August; and on 22 August, Ribbentrop flew to Moscow to conclude a formal non-aggression treaty. Although the treaty is known as the Molotov-Ribbentrop Pact, it was Stalin and Hitler, and not Molotov and Ribbentrop, who decided the content of the treaty. The most important part of the agreement was the secret protocol, which provided for the partition of Poland, Finland, and the Baltic States between Nazi Germany and the Soviet Union and for the Soviet annexation of Bessarabia (then part of Romania, now Moldova). This protocol gave Hitler the green light for his invasion of Poland, which began on 1 September. On 5 March 1940 Lavrentiy Beria gave Molotov, along with Anastas Mikoyan, Kliment Voroshilov and Stalin, a note ordering the execution of 25,700 Polish officers and anti-Soviets, in what has become known as the Katyn massacre.
