The two armies engaged in seesaw battles, with little changes in the frontline along the Yunzaobin River. From September 11 to October 20, the Japanese army was able to advance only five kilometers. At the most intense moments, positions would change hands five times a day. On October 17, the Guangxi Army under Li Zongren and Bai Chongxi finally arrived to join Chiang Kai-shek's Central Army in the battle for Shanghai. The Chinese then staged a final counteroffensive in an attempt to fully consolidate Chinese positions around Dachang and retake the banks of the Yunzaobin River. However, the counteroffensive was poorly coordinated and again the Chinese succumbed to superior Japanese firepower. The Japanese utilized some 700 artillery pieces and 150 bombers for the Dachang operation and the town was totally reduced to rubble. The fighting was so fierce that the Chinese casualty rate per hour was sometimes in the thousands, and some divisions were incapacitated in a matter of just a few days. The fighting continued until October 25, when Dachang finally fell. By then, Chinese troops had no option but to withdraw from downtown Shanghai, which they had held for almost three months.