Editing Chu–Han Contention (section)

== Initial stages ==
[[File:中國古代鎩 (51581179747).png|thumb|Trident polearm, [[Han dynasty]]]]
Xiang Yu's arrangement of the [[Eighteen Kingdoms]] sowed significant dissatisfaction among the anti-Qin rebels as it was marred by [[cronyism]], with many rebel leaders who were either not favored by Xiang Yu or merely absent during the appointment (as they were garrisoned far away from Guanzhong) receiving little to no fiefs at all. His enffeoffment of the [[Guanzhong]] region to three surrendered Qin generals [[Zhang Han (Qin dynasty)|Zhang Han]], [[Sima Xin]] and [[Dong Yi (Qin dynasty)|Dong Yi]] (collectively known as the [[Three Qins]]), who were widely seen as [[traitor]]s by the Qin people after the sacking of Xianyang, essentially destabilized three of the Eighteen Kingdoms from the start. Moreover, the instigated assassination of [[Emperor Yi of Chu|Emperor Yi]], and Xiang Yu's personal arrogance over battlefield prowess and lack of respect for those deemed beneath him further added to the dissents.

=== Rebellions in Qi and Zhao ===
Merely six months after Qin dynasty's collapse, [[Tian Rong]], a [[Qi (state)|Qi state]] noble and rebel leader, was unhappy with how the Qi territories had been split among three kingdoms{{snd}}Qi, Jiaodong and Jibei, collectively known as the Three Qis{{snd}} and himself not receiving anything due to grudges with Xiang Yu, so he waged war against the other kingdoms. He killed Tian Shi, the King of Jiaodong, and Tian An, the King of Jibei. Tian Du, the King of Qi, was defeated by Tian Rong so he fled and joined Xiang Yu. Tian Rong gained control of the Three Qis and became the ruler of the Qi territories.

Tian Rong contacted [[Peng Yue]], a [[grassroots]] rebel leader who also didn't go to Guanzhong to be enfeoffed and ended up with his territory claimed by Xiang Yu, and formed an alliance against Xiang Yu. At the same time, he sent troops to support [[Chen Yu (Eighteen Kingdoms)|Chen Yu]], who had started a rebellion in the former [[Zhao (state)|state of Zhao]]. In 205&nbsp;BCE, Chen Yu defeated [[Zhang Er (Western Han)|Zhang Er]], the King of Changshan, and seized control of his kingdom. Chen Yu then installed [[Zhao Xie]], the King of Dai, as the new ruler of the Zhao territories.

Upon learning of the rebellions in Qi and Zhao, Xiang Yu led his forces north to deal with the rebels.

=== Han conquest of the Three Qins ===
While Xiang Yu was away, Liu Bang, who was never happy with the fiefs forcefully appointed to him, seized the opportunity to attack the [[Three Qins]]' territories in [[Guanzhong]]. During the few months settling in Hanzhong, Liu Bang's deputy [[Xiao He]] discovered a talented military commander named [[Han Xin]], and convinced Liu Bang to make him the [[dayuanshuai|grand marshall]]. Han Xin proposed a strategy to invade Guanzhong by pretending to reconstruct the previously burnt [[gallery road]]s in order to draw the Three Qins' attention towards the [[mountain pass]]es south of Xianyang, while he secretly took a western route through [[Chencang District|Chencang]] (present-day [[Baoji]], [[Shaanxi]]) to surprise the Three Qins. The plan was a huge success and Han Xin defeated the hastily regrouped [[Zhang Han (Qin dynasty)|Zhang Han]], the King of Yong, in two consecutive battles.

Riding on the tide of victory, Liu Bang proceeded to conquer [[Longxi Commandery|Longxi]] (the area in present-day eastern [[Gansu]] located west of [[Mount Liupan|Mount Long]]), [[Beidi Commandery|Beidi]] (northeastern Gansu and [[Ningxia]]) and [[Shang Commandery|Shang]] (around present-day [[Yulin, Shaanxi|Yulin]]). He also sent his men to retrieve his family in [[Pei County|Pei]] (present-day [[Xuzhou]], Jiangsu) and bring them to him from territories controlled by Western Chu. Upon receiving news of Liu Bang's attacks, Xiang Yu sent an army to Yangjia ({{zhi|c=陽夏}}; present-day [[Taikang County]], Henan) to block Liu Bang's forces; he also appointed [[Zheng Chang]] as the King of [[Han (Warring States)|Hán]] to help him cover his flank.

Meanwhile, [[Zang Tu]], the King of [[Yan (state)|Yan]], killed [[Han Guang]], the King of [[Liaodong Commandery|Liaodong]], seized his lands and proclaimed himself the ruler of the Yan territories.

=== Battle of Pengcheng ===
{{main|Battle of Pengcheng}}
In 205&nbsp;BCE, after conquering the Three Qins in the Guanzhong region, Liu Bang advanced to the east of [[Hangu Pass]] to prepare for an attack on the [[Henan]] region. [[Sima Xin]], the King of Sai, [[Dong Yi (Qin dynasty)|Dong Yi]], the King of Di, and [[Shen Yang (Eighteen Kingdoms)|Shen Yang]], the King of Henan, surrendered to Liu Bang. [[Zheng Chang]], the King of [[Han (Warring States)|Hán]], refused to submit to Liu Bang, so Liu Bang sent [[King Xin of Han|Hán Xin]] to attack and defeat him. Liu Bang then replaced Zheng Chang with Hán Xin as the new King of Hán. [[Zhang Er (Western Han)|Zhang Er]], the former King of Changshan, joined Liu Bang after losing his domain to [[Zhao Xie]] and Chen Yu.

In April–May 205&nbsp;BCE, Liu Bang attacked [[Henei Commandery|Henei]] with help from [[Wei Bao]], the King of [[Wei (state)|Western Wei]]. When Liu Bang received news that Xiang Yu had ordered the assassination of [[Emperor Yi of Chu|Emperor Yi]], he held a memorial service for the emperor and accused Xiang Yu of committing [[regicide]], using this incident as political propaganda to justify his war against Xiang Yu.

In May–June 205&nbsp;BCE, Xiang Yu defeated [[Tian Rong]] at Chengyang ({{zhi|c=城陽}}; around present-day [[Ju County]], Shandong). Tian Rong was killed while retreating to [[Pingyuan Commandery|Pingyuan]] (around present-day northwestern Shandong). Although the Kingdom of Qi had surrendered, Xiang Yu still allowed his troops to plunder and loot the Qi territories. Tian Rong's younger brother, [[Tian Heng (Eighteen Kingdoms)|Tian Heng]], made Tian Rong's son [[Tian Guang (Eighteen Kingdoms)|Tian Guang]] the new King of Qi, and continued to put up resistance against Xiang Yu.

Meanwhile, Liu Bang had mustered an army of about 560,000 with support from the kings who had surrendered to him. In September–October 205&nbsp;BCE, the Chu capital, Pengcheng ({{zhi|c=彭城}}; present-day [[Xuzhou]], Jiangsu), fell to a coalition force led by Liu Bang. When Xiang Yu received news that Liu Bang had occupied Pengcheng, he led 30,000 troops to retake Pengcheng. Liu Bang was caught off guard and his army suffered heavy casualties and his family members were captured by Chu forces. After the battle, Liu Bang lost his territorial gains in Chu and the support of his allies.

=== Battle of Jingsuo ===
After their defeat at Pengcheng, the strength of the Han forces decreased drastically. Liu Bang's family members were captured by Xiang Yu's forces and kept as hostages. Many of the kings who had surrendered to Liu Bang earlier defected to Xiang Yu's side after Liu Bang's defeat. The rulers of Qi and Zhao also requested to make peace with Xiang Yu.

Upon reaching Xiayi ({{zhi|c=下邑}}; east of present-day [[Dangshan County]], Anhui) which was guarded by his brother-in-law, Liu Bang reorganised his troops for a retreat. Meanwhile, Han Xin led reinforcements from Guanzhong into central China and defeated a Chu army between Jing County ({{zhi|c=京縣}}) and Suo Village ({{zhi|c=索亭}}), both in present-day [[Henan]].<ref>{{cite book |first=Sima |last=Qian |title=Records of the Grand Historian, Sections: Emperor Gaozu of Han, Xiang Yu, The Marquis of Huaiyin}}</ref> He also put down a rebellion by Wang Wu and Cheng Chu – former Qin generals – and Shen Tu, the magistrate of Wei, and captured their base at Waihuang ({{zhi|c=外黃}}; in present-day [[Minquan County]], Henan).<ref>{{cite book |first=Sima |last=Qian |title=Records of the Grand Historian, Sections: Cao Shen, Fan Kuai, Guan Ying, Jin Xi}}</ref> He and Liu Bang reorganised the Han army and established strong Han garrisons in Xingyang and [[Chenggao]]. Han Xin also developed his plan to conquer northern China, with the aim that Xiang Yu would be too distracted by Liu Bang and his bases of Xingyang and Chenggao to properly counter Han Xin in the north, nor could he endanger his line of retreat by marching past Xingyang and Chenggao into Guanzhong.

Liu Bang then sent a messenger to meet [[Ying Bu]], the King of Jiujiang, to persuade Ying Bu to support him. In November 205&nbsp;BCE, after Han Xin's victory at the [[Battle of Jingxing]], Ying Bu agreed to join Liu Bang and rebelled against Xiang Yu. Upon learning about it, Xiang Yu sent [[Long Ju]] to attack Ying Bu.

In July–August 205&nbsp;BCE, Liu Bang named his son [[Emperor Hui of Han|Liu Ying]] as his heir apparent and put him in charge of Yueyang ({{zhi|c=櫟陽}}; present-day [[Yanliang District]], Xi'an). Shortly after, Han forces conquered Feiqiu ({{zhi|c=廢丘}}; present-day [[Xingping]], Shaanxi), which was guarded by [[Zhang Han (Qin dynasty)|Zhang Han]], who committed suicide after his defeat.

On another front, Ying Bu was unable to resist Long Ju's attacks so he gave up on his domain in Jiujiang and joined Liu Bang.