The treaty was signed in Moscow on April 13 1941, by Foreign Minister Yosuke Matsuoka and Ambassador Yoshitsugu Tatekawa for Japan and Foreign Minister Vyacheslav Mikhailovich Molotov for the Soviet Union.
At a later date, the treaty was expanded to include a declaration regarding Mongolia and Manchuria. The Soviet Union pledged to respect the territorial integrity and inviolability of Manchukuo, while Japan did the same for the Mongolian People's Republic. Still later, in 1941, Japan, as a signatory of the Tripartite Pact, considered denouncing the Soviet-Japanese Neutrality Pact, especially after Nazi Germany invaded the Soviet Union (Operation Barbarossa) at the start of the World War II, but made the crucial decision to keep it and to expand southwards invading the European colonies in Southeast Asia instead.
On April 5 1945 the Soviet Union repudiated the pact, informing the Japanese government that "in accordance with Article Three of the above mentioned pact, which envisaged the right of denunciation one year before the lapse of the five year period of operation of the pact, the Soviet Government hereby makes known to the Government of Japan its wish to denounce the pact of April 13, 1941.
On August 8 1945 the Soviet Union declared war on Japan and launched Operation August Storm keeping their promise to the other Allies at the Yalta Conference to enter the war with Japan three months after the end of World War II in Europe. The Japanese argue that, while the Soviet Union gave notice as outlined in Article Three that the pact would not be renewed, Operation August Storm still violated the treaty as the pact itself remained in effect until April 13, 1946.