In early 1937, Tōngzhōu was capital of the East Hopei Government, a Japanese puppet state controlling the strategic eastern district of Beijing. In July, a detachment of approximately 800 troops of the Chinese 29th Army, under the command of General Sung Che-yuan and loyal to the Kuomintang government, camped outside the walls of Tōngzhōu. Refusing to leave despite the strong protests of the Japanese garrison commander, the Japanese did not know that General Sung had reached an agreement with East Hopei leader Yin Ju-keng, who hoped to use Sung's Kuomintang troops to rid himself of his Japanese overlords.