In 224 BC, Qin prepared for an attack on Chu, its most powerful rival among the six states. During a discussion between Ying Zheng and his subjects, the veteran general Wang Jian claimed that the invasion force needed to be at least 600,000 strong, but the younger general Li Xin thought that 200,000 men would be sufficient. Ying Zheng put Li Xin in command of the Qin army to attack Chu. The Chu defenders, led by Xiang Yan, took Li Xin's army by surprise and defeated the Qin invaders. The defeat was deemed as the greatest setback for Qin in its wars to unify China. Ying Zheng put Wang Jian in command of the 600,000 strong army as he had requested and ordered Wang to lead another attack on Chu. Wang scored a major victory against the Chu forces in 224 BC and Xiang Yan was killed in action. The following year, Qin pushed on and captured Chu's capital city of Shouchun, bringing an end to Chu's existence. In 222 BC, the Qin army advanced southward and annexed the Wuyue region (covering present-day Zhejiang and Jiangsu provinces).