Since the invasion of Manchuria and the creation of the puppet state Manchukuo in 1931, an uneasy truce existed between Japan and China. The Marco Polo Bridge, linking Beijing to Chinese-controlled areas in the south, became the flashpoint for renewed warfare between the Imperial Japanese and nationalist Chinese armies.
Whether this “incident” that provoked full-scale war was intentional or a pretext for the invasion of China is a matter of historical debate. Nevertheless, the agenda of right wing Japanese proponents of expansion (“Asia for the Asians”) was advanced.