How did the Mukden Incident lead to Japan’s invasion of Manchuria?

The Mukden Incident was a contrived event orchestrated by the Japanese Kwantung Army on September 18, 1931, to serve as a pretext for the invasion of Manchuria.1

Japanese officers staged an explosion along the South Manchurian Railway near the city of Shenyang (then Mukden). Although the blast caused minimal damage, the Japanese military used it as a false justification to launch artillery attacks on a nearby Chinese garrison and occupy the city.1

This action was taken without the authorization of the Japanese civil government. Despite a stated policy of nonexpansion from Tokyo, the Kwantung Army continued to advance throughout northern Manchuria, meeting little resistance due to Chinese leader Chiang Kai-shek’s policy of nonresistance and withdrawal. Within three months, Japanese troops had spread across the region, eventually leading to the establishment of the puppet state of Manchukuo. This act of aggression violated international norms and contributed significantly to Japan's subsequent isolation and the eventual path toward World War II.1