Political map of East Asia and the Western Pacific 7 July 1937 (Marco Polo Bridge Incident): Many Chinese Nationalists (Kuomintang) saw Japan as the main threat and were unhappy with Chiang Kaishek's focus on destroying the Communists (Long March). In late 1936, they stepped in to force him to accept a United Front against Japan (Xian Incident). Conflict erupted in Beiping (then the name for Beijing) in July the next year, when edgy Nationalist troops fired on Japanese performing military maneuvers at Marco Polo Bridge (Marco Polo Bridge Incident).