important region due to its rich natural resources including coal, fertile soil, and various minerals. For pre–World War II Japan, Manchuria was an essential source of raw materials. Without occupying Manchuria, the Japanese probably could not have carried out their plan for conquest over Southeast Asia or taken the risk of attacking the United States and the British Empire in 1941. There was a major epidemic known as the Manchurian plague in 1910–1911, likely caused by the inexperienced hunting of marmots, many of whom are diseased. The cheap railway transport and the harsh winters, where the hunters sheltered in close confinement, helped to propagate the disease. The response required close coordination between the Chinese, Russian and Japanese authorities and international disease experts held an 'International Plague Conference' in the northern city of Shenyang after the disease was under control to learn the lessons. It was reported that among Banner people, both Manchu and Chinese (Hanjun) in Aihun, Heilongjiang in the 1920s, would seldom marry with Han civilians, but they (Manchu and Chinese Bannermen) would mostly intermarry with each other. Owen Lattimore reported that during his January 1930 visit to Manchuria, he studied a community in Jilin (Kirin), where both Manchu and Chinese Bannermen were settled at a town called Wulakai, and eventually the Chinese Bannermen there could not be differentiated from Manchus since they were effectively Manchufied (assimilated). The Han civilian population was in the process of absorbing and mixing with them when Lattimore wrote his article. Around the time of World War I, Zhang Zuolin established himself as a powerful warlord with influence over most of Manchuria. During his rule, the Manchurian economy grew tremendously, backed by the immigration of Chinese from other parts of China. The Japanese assassinated him on 2 June 1928, in what is known as the Huanggutun Incident. Following the Mukden Incident in 1931 and the subsequent Japanese invasion of Manchuria, the Japanese declared Inner Manchuria an "independent state", and appointed the deposed Qing emperor Puyi as puppet emperor of Manchukuo. Under Japanese control, Manchuria was brutally run, with a systematic campaign of terror and intimidation against the local populations including arrests, organised riots and other forms of subjugation. Manchukuo was used by Japan as a base to invade the rest of China. At that time, hundreds of thousands of Japanese settlers arrived in Manchuria. After the atomic bombing of Hiroshima, Japan in 1945, the