by Qin. Defeat The Chu state was completely eradicated by the Qin dynasty. According to the Records of the Warring States, a debate between the Diplomat strategist Zhang Yi and the Qin general Sima Cuo led to two conclusions concerning the unification of China. Zhang Yi argued in favor of conquering Han and seizing the Mandate of Heaven from the powerless Zhou king would be wise. Sima Cuo, however, considered that the primary difficulty was not legitimacy but the strength of Qin's opponents; he argued that "conquering Shu is conquering Chu" and, "once Chu is eliminated, the country will be united". The importance of Shu in the Sichuan Basin was its great agricultural output and its control over the upper reaches of the Yangtze River, leading directly into the Chu heartland. King Huiwen of Qin opted to support Sima Cuo. In 316 BCE, Qin invaded and conquered Shu and nearby Ba, expanding downriver in the following decades. In 278 BCE, the Qin general Bai Qi finally conquered Chu's capital at Ying. Following the fall of Ying, the Chu government moved to various locations in the east until settling in Shouchun in 241 BCE. After a massive two-year struggle, Bai Qi lured the main Zhao force of 400,000 men onto the field, surrounding them and forcing their surrender at Changping in 260 BCE. The Qin army massacred their prisoners, removing the last major obstacle to Qin dominance over the Chinese states. By 225 BCE, only four kingdoms remained: Qin, Chu, Yan, and Qi. Chu had recovered sufficiently to mount serious resistance. Despite its size, resources, and manpower, though, Chu's corrupt government worked against it. In 224 BCE, Ying Zheng called for a meeting with his subjects to discuss his plans for the invasion of Chu. Wang Jian said that the invasion force needed to be at least 600,000 strong, while Li Xin thought that less than 200,000 men would be sufficient. Ying Zheng ordered Li Xin and Meng Wu to lead the army against Chu. The Chu army, led by Xiang Yan secretly followed Li Xin's army for three days and three nights, before launching a surprise offensive and destroying Li Xin army. Upon learning of Li's defeat, Ying Zheng replaced Li with Wang Jian, putting Wang in command of the 600,000-strong army he had requested earlier and placing Meng Wu beneath him as a deputy. Worried that the Qin tyrant