How did the prelude of "August 13th" Battle of Songhu begin?

On the afternoon of August 1937, under the command of General Sun, the 262nd Brigade of the 88th Division quickly seized the position from North Railway Station to Jiangwan with lightning speed. I saw strong roadblocks built in the street and the soldiers entered a state of war. The Japanese army is unwilling to be lonely. While the defenders of China seized positions, they also built positions from Hongkou to Sichuan North Road. Bazi Bridge, a traffic fortress outside Shanghai, is an important stronghold for the success or failure of the campaign. There was a fierce gun battle between China and Japan for this figure-of-eight bridge. At 4 o'clock in the afternoon, the warship moored outside Wusongkou suddenly slammed into Zhabei area with heavy artillery. In an instant, the dangerous buildings in Zhabei area collapsed, and the smoke brought piles of rubble and people's cries. It kicked off the "August 13th" Battle of Songhu.