Many commentaries, focused on the use of atomic weapons, suggest that use of such weapons of mass destruction was not necessary given that Japan was attempting to open peace negotiations via the Soviets as intermediaries. As noted in earlier posts, if one wishes to assert that peace negotiations via the Soviets was a viable pathway, one needs to account for the history of Japanese-Soviet relations which in general had always been contentious. Military actions include the 1903-1905 Japanese-Soviet war which concluded with a resounding Japanese victory at the naval battle of Tsushima, the 1939 Japanese invasion (unsuccessful) of Soviet-held Mongolia, and a long history of border conflict in northern Manchuria and Siberia.

The 1939 German–Soviet Non-Aggression Pact surprised Japan. Berlin, its nominal Axis partner, had essentially made peace with Moscow just as Japan had been fighting the Soviets. This left Tokyo diplomatically exposed. With tensions high, both Japan and the USSR had reasons to avoid a two-front war. The Soviets feared German aggression. By securing peace with Japan in the east, he could concentrate forces in the west. A neutrality pact would allow Japan to focus on expansion southward (toward Indochina, the Dutch East Indies, the Philippines) without worrying about Siberia. The pact was signed on April 13, 1941. Both sides pledged to respect each other’s territorial integrity and neutrality if either was attacked by a third power. On April 5, 1945 the Soviets informed Japan that they would not renew the pact in April 1946. But on the same day, the Soviets began deploying approximately 1 million soldiers to the Far East in fulfillment of a 1943 pledge to the Allies to enter the Asia-Pacific war within 3 months of the surrender of Germany.