On 7 July 1937, the 29th Army and the Japanese army in China exchanged fire at the Marco Polo Bridge near the Wanping Fortress southwest of the city. The Marco Polo Bridge Incident triggered the Second Sino-Japanese War, World War II as it is known in China. During the war, Beijing fell to Japan on 29 July 1937 and was made the seat of the Provisional Government of the Republic of China, a puppet state that ruled the ethnic-Chinese portions of Japanese-occupied northern China. This government was later merged into the larger Wang Jingwei government based in Nanjing.