The assault on the city begun at the night of May 23, 1949 when the communist 29th Army took the high ground in the southern suburb under the cover of darkness, while the communist 28th Army penetrated to Wusong and shelled the pier. On May 24, 1949, the communist 20th Army took Pudong and the communist 27th Army took the train station at Xujiahui and Hongqiao. The nationalist commander-in-chief, Tang Enbo already boarded naval ships on May 18, 1949, realized the inevitable and in order to strengthen the defense around the pier at Wusong, ordered the surviving 6th Division of the nationalist 75th Army at Gaoqiao to withdraw to Yuepu, and the nationalist units north of Suzhou Creek to withdraw to Wusong, for the preparation to withdraw via sea.