On the morning of December 13, 1937, four divisions of the Japanese army and two navy fleets on the Yangtze River invaded Nanjing. The capital city now became one of the largest cities under the Japanese Central China Area Army (CCAA). The prewar population of over one million had shrunk considerably by November as the Japanese army advanced. On the morning of the 13th approximately 500,000 Chinese still remained. These were largely the poor who had little alternative while those able to leave had either financial resources or a place to go west of Nanjing.