Manchukuo (満州国 Manshuukoku 'State of Manchuria') was the Japanese name for Manchuria (Northeast China, Chinese 東北 Dōngběi), and refers to Japanese control of the region in the 20th century, especially 1931-45 when a Japanese puppet state of the same name was in operation. The United States rejected Japanese control and it became one of many issues that led to declining foreign relations between the U.S. and Japan during the 1930s and 1940s. In 1946, the region was returned to the control of China.
The Japanese Kwangtung Army was initially in the Kwangtung Leasehold on the border of Manchuria. Threatened by the growth of Chinese nationalism in Manchuria, the officers of the Kwangtung Army staged the Manchurian Incident on Sept. 18, 1931, occupied all of Manchuria, and, on Feb. 18, 1932, created the puppet state of Manchukuo.
Concerned less with who controlled Manchuria than with Japanese violations of the Nine Power Treaty and the Pact of Paris (1927), the United States, independently and in concert with the League of Nations, exerted pressure on Japan. Foreign protests were ignored by the Japanese military, and the civilian government was unable to restrain the army. With none of the powers willing to impose sanctions, the U.S. Secretary of State Henry Stimson announced in January 1932 the "Stimson Doctrine"--a refusal to recognize conditions brought about by Japanese treaty violations.
Japanese politicians and intellectuals implemented plans for cultural assimilation and integration of culturally Chinese Manchurians into the Japanese empire through direct print and film propaganda efforts, which were aimed at the women of Manchukuo. The efforts were reversed after Japan's defeat in 1945.
Japan and the Soviet Union fought a large-scale border war in Manchukuo in 1939, resulting in a major Soviet victory at Nomonhan, and Japanese reluctance to engage the Soviets any more. Japan thereupon turned south.
During World War II
1945 and after
With the defeat of Japan in 1945, Manchukuo ceased to exist as an "independent" entity. At Yalta in February 1945, President Franklin D. Roosevelt secretly agreed to give this region to the Soviet Union in return for Soviet intervention in the war in Asia. The Soviet Red Army entered Manchuria in August 1945 and remained there until April 1946. After Soviet forces withdrew, Mao Zedong and his People's Liberation Army defeated Chiang Kai-shek's Kuomintang armies in Manchuria as in the rest of China, and Manchuria was again politically a part of China.
- Alvin D. Coox, Nomonhan: Japan Against Russia, 1939 (1985).