During the Japanese occupation of Manchuria, the Oroqen suffered a significant population decline. The Japanese distributed opium among them and subjected some members of the community to human experiments, and combined with incidents of epidemic diseases this caused their population to decline until only 1,000 remained. The Japanese banned Oroqen from communicating with other ethnicities, and forced them to hunt animals for them in exchange for rations and clothing which were sometimes insufficient for survival, which lead to deaths from starvation and exposure. Opium was distributed to Oroqen adults older than 18 as a means of control. After 2 Japanese troops were killed in Alihe by an Oroqen hunter, the Japanese poisoned 40 Oroqen to death. The Japanese forced Oroqen to fight for them in the war which led to a population decrease of Oroqen people. Even those Oroqen who avoided direct control by the Japanese found themselves facing conflict from anti-Japanese forces of the Chinese Communists, which contributed to their population decline during this period.