The Soviet Union invades Manchuria and helps force Japan's surrender
Operation August Storm crushes the Kwantung Army in under two weeks
Quick facts
- Location
- Manchuria and Inner Mongolia
- Date invasion began
- August 9, 1945
- Soviet forces
- About 1.5 million troops
- Commander
- Marshal Aleksandr Vasilevsky
- Result
- Collapse of the Kwantung Army within days
What happened
On August 8, 1945, the Soviet Union declared war on Japan, honoring a commitment made at the Yalta Conference to enter the Pacific war within three months of Germany's defeat, and early on August 9, hours after the atomic bombing of Nagasaki and three days after Hiroshima, roughly 1.5 million Red Army troops swept across the border into Japanese-occupied Manchuria and Inner Mongolia. Facing them was Japan's Kwantung Army, nominally over 700,000 to 900,000 men but hollowed out by years of transfers to other Pacific fronts and short on modern equipment. Soviet armored columns under Marshal Aleksandr Vasilevsky executed a pincer movement across the Gobi Desert and the Greater Khingan mountains, and Japanese resistance in Manchuria collapsed within days.
Why it matters
The rapid destruction of the Kwantung Army, long considered Japan's most capable ground force, removed any remaining illusion in Tokyo that the war could be continued on the Asian mainland, and historians weigh the Manchurian invasion alongside the atomic bombings as a decisive factor in Japan's decision to surrender on August 15. It also gave the Soviet Union a postwar foothold in Manchuria and Korea that shaped the early Cold War in East Asia.
How we know
The Harry S. Truman Presidential Library's education archive documents the Yalta commitment and the timing of the Soviet declaration of war relative to the atomic bombings, drawn from the Potsdam and Yalta conference records.
Sources
- Imperial War Museums. The Soviet invasion of Manchuria · Reputable sourceiwm.org.uk · The domain "iwm.org.uk" is on our Reputable source registry.
- Harry S. Truman Presidential Library and Museum. Invasion of Manchuria · Primary source (author-declared)trumanlibrary.gov · Cited as a "primary" source (no stronger domain match).
- History.com. Soviets declare war on Japan, invade Manchuria · Reputable sourcehistory.com · The domain "history.com" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
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