Manchuria is a region of northeast China that was conquered by Japan between 1931-1932 as part of its imperial expansion. Japan faked an incident between Chinese and Japanese soldiers at Mukden to justify its invasion. It then renamed the conquered territory Manchukuo. The League of Nations condemned Japan's invasion and sent a commission to investigate, but Japan responded by leaving the League in 1933, revealing the League's inability to stop determined acts of aggression.