Japanese military train illustration, 1930s

We think this refers to what is known as the Manchurian Incident, an event staged by Japanese military personnel as a pretext for invading the northern part of China known as Manchuria: on 18 September 1931, a small quantity of dynamite was detonated close to a railway owned by Japan's South Manchuria Railway near Mukden (now Shenyang). Although the explosion was so weak that it failed to destroy the lines and a train passed over the area minutes later, the Japanese Army, accusing Chinese dissidents of the act, invaded and occupied Manchuria, in which Japan established its puppet state of Manchukuo six months later. The ruse was soon exposed to the international community, leading Japan to diplomatic isolation and its March 1933 withdrawal from the League of Nations.