Franco-Soviet Treaty of Mutual Assistance
The Franco-Soviet Treaty of Mutual Assistance was a 1935 bilateral treaty between France and the Soviet Union with the aim of enveloping Nazi Germany and reducing the military threat from Central Europe. It was pursued by Maxim Litvinov, the Soviet foreign minister, and Louis Barthou, the French foreign minister, who was assassinated in October 1934, before negotiations had been finished.
Source: Wikipedia — Franco-Soviet Treaty of Mutual Assistance (CC BY-SA 4.0)