The Tripartite Pact was the culmination of a series of agreements between Germany, Japan, and Italy. On October 25, 1936, Germany and Italy completed the Rome-Berlin Axis, a cooperation deal. A month later Japan joined the so-called Axis powers by signing (with Germany) the Anti-Comintern Pact, an anti-communist agreement that was primarily directed against the Soviet Union; Italy signed in 1937. However, that compact was broken with the German-Soviet Nonaggression Pact of August 23, 1939, which paved the way for Germany to invade Poland the following week, thus starting World War II.