Later in 1941, Japan would consider breaking the pact when Nazi Germany invaded the Soviet Union in Operation Barbarossa, but they made the crucial decision to keep it and to continue to press into Southeast Asia instead. This was said to be largely due to the Battle of Khalkhin Gol. The defeat there caused Japan not to join forces with Germany against the Soviet Union, even though Japan and Germany were part of the Tripartite Pact. On April 5, 1945, the Soviet Union unilaterally denounced the neutrality pact, noting that it would not renew the treaty when it expired on April 13, 1946. Four months later, prior to the expiration of the neutrality pact, and between the atomic bombings of Hiroshima and Nagasaki, the Soviet Union declared war on Japan, completely surprising the Japanese. The Soviet invasion of Manchuria was launched one hour after the declaration of war.