The collapse of the Qin Dynasty meant the failure of the county system, and after the uprising of Chen Sheng and Wu Guang, the nobles of the Six Kingdoms had already returned to the country, and basically quickly took control of their original territory. After the death of Chen Sheng and Wu Guang, it was even more so, even the state of Chu, which first raised the banner of anti-Qin, also returned to the original state of being a nobleman as the king, and some of the princes and kings established by Chen Sheng were quickly killed, and generally returned to the state before Qin destroyed the Six Kingdoms.
By the time Liu Bang and Xiang Yu were ordered to go north to rescue Zhao, it was already completely the pattern before the Six Kingdoms, Zhang Han defeated the Chu army and killed Xiang Liang, basically along the route of the previous Qin to destroy the Six Kingdoms, and continued to attack eastward, as long as the relatively strong Zhao State was defeated at that time, the Kwantung countries had no main force to resist Qin, but in the Battle of Julu, Xiang Yu broke the cauldron, defeated the Qin army, and forced Zhang Han's 200,000 people to surrender, and the situation was reversed.
After that, according to the agreement of King Chu Huai, the first to enter the pass is the king, Xiang Yu led the army to confront Zhang Han's Qin army, and Liu Bang led his troops to directly attack the Qin state's hometown in Guanzhong, and finally succeeded in breaking through the Qin army's defense line and entering the pass, the prince of Qin surrendered, and the Qin state perished. According to the previous agreement of King Chu Huai, then Liu Bang should be the king of Qin. Xiang Yu was not convinced, and led his troops to defeat the defenders sent by Liu Bang to Hangu Pass, and demolished Hangu Pass, entered Guanzhong, and burned and plundered, and then assembled the princes and adjusted the fiefs of various countries.
Because Xiang Yu's main purpose in adjusting the fiefdoms of various countries was to weaken other countries, so the original countries were divided, and what he left to himself was the core territory of Chu State, and he himself was the overlord of Western Chu, so as soon as he returned to the capital Pengcheng, the other vassal states began to attack each other, and the world was in chaos again, and Xiang Yu first led his troops north to attack Qi State, Liu Bang took the opportunity to return to Guanzhong from Hanzhong, eliminated Sanqin, and sent Han Xin to lead troops to attack Zhao State and Qi State's hometown, and he himself led his troops straight to Pengcheng.
In the process of the struggle between Chu and Han, the princes of various countries also chose sides between Xiang Yu and Liu Bang, Liu Bang while co-opting those princes who opposed Xiang Yu, while eliminating the princes who were still on Xiang Yu's side, and finally even Xiang Yu's own feudal Jiujiang King Yingbu and other princes betrayed Xiang Yu, and Xiang Yu, who rebelled against his relatives, was finally defeated by Han Xin in the battle of Qixia, and he himself committed suicide after fleeing to the Wujiang River. The Chu-Han rivalry ended in Liu Bang's victory, and at this time a large number of former princes were still retained, as well as his own canonized princes such as Han Xin, the king of Qi.
Therefore, after defeating Xiang Yu, Liu Bang then began to attack the king with a different surname, and finally eliminated the king with a different surname represented by Han Xin, Yingbu and Peng Yue, and sent his own sons and nephews to various places as princes and kings to guard, and agreed that if it was not the Liu family, it would not be the king, otherwise the world would attack it together. At this time, the princes and kings of Liu Bang were divided, and the further southeast they went, the larger the territory, and most of the princes and kings were only the size of the territory after Xiang Yu's partition.
After Liu Bangding was in Guanzhong, the Guanzhong region and some areas on the Central Plains that could be directly controlled, mainly some places in Korea and Wei, basically adopted the management method of direct central government, that is, the county system, and other places where the central government was still beyond the reach of the whip at that time, the sub-feudal system was retained, but the princes and kings were all Liu's sons and nephews to maintain the stability of the whole country. In other words, the coexistence of the feudal system and the county system in the early Han Dynasty was not designed by Liu Bang, but a problem left over from history.