Around 9 am on August 13, the Chinese Peace Preservation Corps exchanged small arms fire with Japanese troops in the Zhabei, Wusong, and Jiangwan districts of Shanghai. At about 3 pm the Japanese army crossed over the Bazi Bridge (八字橋) in Zhabei and attacked various centers in the city. The 88th Division retaliated with mortar attacks. Sporadic shooting continued through the day until 4 pm, when Japanese headquarters ordered ships of the Third Fleet stationed in the Yangtze and the Huangpu River to open fire on Chinese positions in the city. Late that night, Chiang Kai-shek ordered Zhang Zhizhong to begin Chinese offensive operations the next day. The next morning the Republic of China Air Force (ROCAF) began bombing various Japanese targets and Chinese ground forces attacked at 3 pm. On the same day, August 14, the Chinese government issued the Proclamation of Self-Defense and War of Resistance (自衛抗戰聲明書), explaining the government's resolution against Japanese aggression. The Battle of Shanghai had officially begun.