Final answer:
The Soviet Union invaded Manchuria when it declared war on Japan in 1945.
Step-by-step explanation:
The correct answer is OB. Manchuria.
When the Soviet Union declared war on Japan in 1945, it invaded Manchuria, which was a Japanese-occupied territory at the time. This invasion was part of the Soviet Union's effort to fulfill its agreement with the Allied powers to join the war against Japan after Germany's surrender in World War II.
The Soviet invasion of Manchuria played a crucial role in Japan's decision to surrender and marked the beginning of the end of World War II.
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