Manchuria was a province in the north-east of China, bordering Russia to the north and Shangdong province to the south. In the early 20th century, it was threatened with trade strangulation by a new Russian railway stretching from Europe to the Pacific port of Vladivostok.
In 1931, Japan invaded Manchuria in order to expand their Empire and gain control of China's natural resources, but also ostensibly to restore order to a China embroiled in a struggle between Nationalists and Communists, and to attract trade back to the region. After the invasion, Manchuria was reorganised into the puppet state of Manchukuo, ruled by the ousted Chinese Emperor Pu Yi. The Kwantung Army occupied the region and Kwantung Army Intelligence established itself at Hsinking. Chinese people continued to refer to the region as Manchuria. (PROSE: The Shadow of Weng-Chiang)
Peasants in Manchukuo were subjugated by the Kwantung Army and forced to work on the construction of Zhong Ma fortress, where Japanese military scientists sought to develop biological weapons. The Seventh Doctor and Edward Grainger travelled to the region in 1933 to rescue Mai Ling from the fortress (PROSE: Log 384)
Disputes over the province continued deeper into the 1930s. (PROSE: The Year of Intelligent Tigers) The Kodo Ha and Tosei Ha factions of the Imperial Japanese Army both favoured further expansion in Manchukuo, the former to offset strategic advantages enjoyed by the Soviet Union and the latter to act against China.
When World War II began in Asia in July 1937, the front lines opened up in Manchukuo, with the Japanese Twelfth Army pushing south into Shangdong, although their immediate aim was further consolidation of Manchuria. (PROSE: The Shadow of Weng-Chiang)