be immediately executed. This doomed the Taiping army and Nanking by creating widespread discontent and, coupled with other factors, eventually over 200,000 Taiping troops went out of Nanking and surrendered to the Imperial Chinese army during the course of the battle. Those who refused to surrender but were also upset by Hong's decisions chose to break out while they still could, when the siege was still incomplete. Hong, Li and others were unable to stop such acts. On February 28, 1864, Tianbao () Castle at the highest peak of the Purple Mountain fell under the Qing army's control. On March 2, Zeng Guoquan deployed his troops to Shence and Taiping Gates. The siege of Nanking was completed. The battle On March 14, Zeng Guoquan attempted his first attack on Nanking using ladders, but this was beaten back by the defenders. The imperial army then changed tactics, digging a total of ten tunnels at Chaoyang (), Shence and Jinchuan () Gates, and the defenders in turn countered by digging tunnels of their own and building a secondary wall behind the first. Five days after the death of Hong Xiuquan on June 1, 1864, Li Xiucheng was finally put in charge of all military and political affairs, but it was already too late—the fate of the city and its defenders was sealed. On July 3, Dibao Castle (地保城, nicknamed Dragon's Neck 龙脖子) on the Purple Mountain fell into the Qing army's hands. This strategic location enabled the Qing to build several dozen artillery positions to bombard the entire city, thus suppressing the defenders' firepower and providing cover for other preparations to take the city. One tactic of the attackers was to fill the space between the city wall and the mountain ridge at the Dragon's Neck with earth, sand, logs, rocks and grass, so the land surface was raised to the height of the city wall, thus paving the way to attack the city. Another was to dig tunnels just 200 feet away from the city wall so that they could be filled with explosives to blow up the wall. Operations within such close proximity of enemy fire were possible due to sufficient covering fire, thanks to the taking of Dibao Castle. The defenders' attempts to disrupt the preparations were continuously beaten back with heavy losses due to withering fire from the attackers. Two weeks later the preparation was complete. Realizing the