The event that led the japanese to invade the chinese province of manchuria was the Mukden Incident.
The Japanese invasion of Manchuria kicked of on 18 September 1931, when the Kwantung Army of the Empire of Japan invaded Manchuria right after the Mukden Incident. Following the war, the Japanese established the puppet state of Manchukuo.
The Mukden Incident was an event carried out by Japanese military personnel as an excuse to invade northeastern China, known as Manchuria in 1931.
