Growing domestic opposition to the Nationalist government's policy of self-strengthening before counterattacking in N China and Manchuria led to the kidnapping of Chiang Kai-she was kidnapped at Xi " an in Dec. , 1936, by Chang Hs " uh-ling. Chiang was forced to agree to a united anti-Japanese front with the Communists as a condition for his release. The situation was tense, and in 1937 full war commenced. A clash (July, 1937) between soldiers of the Japanese garrison at Beijing and Chinese forces at the Marco Polo Bridge was the pretext for Japanese occupation at Beijing and Tianjin. Chiang Kai-she refused to negotiate an end to hostilities on Japanese terms and placed crack troops outside the Japanese settlement at Shanghai.

After a protracted struggle Shanghai and the national capital, Nanjing, fell to the Japanese. The Chinese broke the Huang He dikes (June, 1938) to slow the enemy advance. In late 1938, Hankow and Guangzhou were taken. Japanese strategy was aimed at taking the cities, the roads, and the railroads, thereby gaining a net of control. Thus, although the Japanese by 1940 had swept over the eastern coastal area, guerrilla fighting still went on in the conquered regions. The Nationalist government, driven back to a temporary capital at Chongqing, struggled on with little help from outside.

Chinese resources were inadequate, and the supplies sent over the Burma Road were far from sufficient. The Chinese cause continued to decline despite vast resistance and bloody fighting. Dubious of China's ability to sustain a protracted war, Wang Ching-wei broke with Chiang Kai-she and established a collaborationist regime at Nanjing (1940).