When the Nationalist capital of Nanjing fell to the Japanese on 13 December 1937, Zhou accompanied the Nationalist government to its temporary capital of Wuhan. As the chief representative of the CCP in the nominal KMT-CCP cooperation agreement, Zhou established and headed the official KMT-CCP liaison office. While running the liaison office, Zhou established the Yangtze Bureau of the Central Committee. Under cover of its association with the Eighth Route Army, Zhou used the Yangtze Bureau to conduct clandestine operations within southern China, secretly recruiting Communist operatives and establishing Party structures throughout KMT-controlled areas.