 On April 9 Chiang declared martial law in Shanghai and the Central Control Commission issued the "Party Protection and National Salvation" proclamation, denouncing the Wuhan Nationalist Government's policy of cooperation with the CPC.On April 11 Chiang issued a secret order to all provinces under the control of his forces to purge Communists from the KMT.Before dawn on April 12, gang members began to attack district offices controlled by the union workers, including Zhabei, Nanshi and Pudong.