Members of the New Fourth Army wore their badges on the left arm, with "N4A" and the soldier's unit and name listed on the badge. After the Xi'an Incident, the Kuomintang led by Chiang Kai-shek and the Communist Party of China led by Mao Zedong formed a United Front against Japan, which was already in control of Manchuria and pushing into North China. The Marco Polo Bridge Incident in July 1937 marked the beginning of the Sino-Japanese War (1937-1945).