The battle of Lantian (207 BC) saw a rebel army led by Liu Bang defeat one of the last Qin armies, a defeat that exposed the Qin heartland to conquest and ended the short-lived Qin dynasty.
The Qin dynasty had been founded by the First Emperor, but after his death in 210 BC a series of revolts had broken out. Qin armies won a number of victories, but were unable to subdue all of the rebels. During 208 BC the main rebel army was split, with part going north to lift the siege of Julu and part, under Liu Bang, going west to attack Qin and threaten the Imperial capital of Xianyang.
Late in 208 Liu Bang entered the Qin heartland. By this point the most able Qin general, Zhang Han, had surrendered to the most important rebel leader, Xiang Yu, and it was becoming clear that the Qin were doomed. Zhao Gao, the power behind the throne, forced the Second Emperor to kill himself. He then attempted to negotiation with Liu Bang, offering to make him ruler of part of Qin. When this effort failed Zhao Gao make Ying Ziying, probably a nephew of the Second Emperor, king of Qin (as the Infant Ruler). Ying Ziying was not as passive as Zhao Gao might have hoped. He had Zhao killed, and sent an army to try and block the Yao Pass, one of the last natural obstacles between Liu Bang and the Qin capital of Xianyang.
Liu Bang’s initial instinct was to attack the troops blocking the pass, but Zhang Liang, one of his long-standing advisors, came up with an alternative plan. He argued that the Qin troops were still very strong, and a frontal assault should be avoided. Instead two of Liu Bang’s other advisors – Lu Jia (an established advisor) and Li Yiji (a gatekeeper to a local village who had offered advice that helped Liu Bang earlier in the campaign) should be sent to negotiation with the Qin generals, while in the pass Liu Bang’s men should display a larger number of flags and banners than normal in an attempt to demoralise the Qin troops.
The negotiations with the Qin generals went well, but now Zhang Liang appears to have changed his mind. He now suggested that only the generals wanted to change sides, and that the Qin soldiers would fight on. Instead of negotiating he suggested that Liu Bang move around the pass, taking a different route into the Qin heartlands, and then attack the Qin army while they were demoralised.
This plan worked perfectly. Liu Bang won two victories at Lantien, the first to the south of the city and the second to its north. He then advanced towards the capital, but these victories had broken the last Qin resistance. Early in December Ying Ziying surrendered to Liu Bang, ending the Qin dynasty. He was treated well by Liu Bang, but late in January 206 BC he was killed on the orders of Xiang Yu, the acknowledged leader of the rebels.
The defeat of the Qin was followed almost immediately by the Chu-Han Contention (206-202 BC) which saw Liu Bang and Xiang Yu struggle for control of China, and that ended with the victory of Liu Bang and the foundation of the Han Dynasty.