Japan invaded Manchuria in 1931 because after the end of World War One, Japan had acquired many new colonies, such as those in the Pacific. This resulted in a large population
… growth, Manchuria would be able to accommodate the over-spill of Japanese civilians. As a result of the population growth also, Japan was having to import many more goods such as food and raw materials. This triggered a desire for Japan to become self-sufficient, and Manchuria was an area of many natural resources such as oil and coal, which would have aided greatly in the Japanese reaching of autarky. Japan was suffering from an economic decline also, Japan was over-producing rice, and its value dropped greatly. The cost of silk, which was mainly exported to the USA also dramatically fell during the Depression to about one-fifth of the price it had been before By invading Manchuria, Japan would be helped in overcoming these economic difficulties, as they would acquire more wealth. Japan also had a very large and strong armed forces, that had a great image in comparison to the weaknesses of the government, who appeared to be failing in dealing with the poor economic climate. The Army generals decided to invade Manchuria to expand their military control. To do this they set up the Mukden Incident, where there was an explosion on the South Manchurian Railway line, an area considered to be owned by the Japanese. The Japanese were able to accuse the Chinese of sabotage, giving themselves a reason to invade the province of China. (MORE) 
