History of the Han dynasty
The Han dynasty was the second imperial dynasty of China. It followed the Qin dynasty, which had unified the Warring States of China by conquest. It was founded by Liu Bang. The dynasty is divided into two periods: the Western Han and the Eastern Han, interrupted briefly by the Xin dynasty of Wang Mang. These appellations are derived from the locations of the capital cities Chang'an and Luoyang, respectively. The third and final capital of the dynasty was Xuchang, where the court moved in 196 CE during a period of political turmoil and civil war.
The Han dynasty ruled in an era of Chinese cultural consolidation, political experimentation, relative economic prosperity and maturity, and great technological advances. There was unprecedented territorial expansion and exploration initiated by struggles with non-Chinese peoples, especially the nomadic Xiongnu of the Eurasian Steppe. The Han emperors were initially forced to acknowledge the rival Xiongnu Chanyus as their equals, yet in reality the Han was an inferior partner in a tributary and royal marriage alliance known as heqin.
This agreement was broken when Emperor Wu of Han launched a series of military campaigns which eventually caused the fissure of the Xiongnu Federation and redefined the borders of China. The Han realm was expanded into the Hexi Corridor of modern Gansu, the Tarim Basin of modern Xinjiang, modern Yunnan and Hainan, modern northern Vietnam, modern North Korea, and southern Outer Mongolia. The Han court established trade and tributary relations with rulers as far west as the Arsacids, to whose court at Ctesiphon in Mesopotamia the Han monarchs sent envoys. Buddhism first entered China during the Han, spread by missionaries from Parthia and the Kushan Empire of northern India and Central Asia.
From its beginning, the Han imperial court was threatened by plots of treason and revolt from its subordinate kingdoms, eventually ruled only by royal Liu family members. Initially, the eastern half of the empire was indirectly administered through large semi-autonomous kingdoms which pledged loyalty and a portion of their tax revenues to the Han emperors, who ruled directly over the western half of the empire from Chang'an. Gradual measures were introduced by the imperial court to reduce the size and power of these kingdoms, until a reform of the middle 2nd century BCE abolished their semi-autonomous rule and staffed the kings' courts with central government officials.
Yet much more volatile and consequential for the dynasty was the growing power of both consort clans and the eunuchs of the palace. In 92 CE, the eunuchs entrenched themselves for the first time in the issue of the emperors' succession, causing a series of political crises which culminated in 189 CE with their downfall and slaughter in the palaces of Luoyang. This event triggered an age of civil war as the country became divided by regional warlords vying for power. Finally, in 220 CE, the son of an imperial chancellor and king accepted the abdication of the last Han emperor, who was deemed to have lost the Mandate of Heaven according to Dong Zhongshu's cosmological system that intertwined the fate of the imperial government with Heaven and the natural world. Following the Han, China was split into three states: Cao Wei, Shu Han, and Eastern Wu; these were re-consolidated into one empire by the Jin dynasty.
Fall of Qin and Chu–Han contention
Collapse of Qin
The Zhou dynasty had made the state of Qin in Western China as an outpost to breed horses and act as a defensive buffer against nomadic armies of the Rong, Qiang, and Di peoples. After conquering six Warring States by 221 BCE, the King of Qin, Ying Zheng, unified China under one empire divided into 36 centrally-controlled commanderies. With control over much of China proper, he affirmed his enhanced prestige by taking the unprecedented title huangdi, or 'emperor', known thereafter as Qin Shi Huang. Han-era historians would accuse his regime of employing ruthless methods to preserve his rule.File:Group of soldiers.jpg|thumb|left|Qin dynasty soldiers from the Terracotta Army of Qin Shi Huang's mausoleum, located near Xi'an
Qin Shi Huang died of natural causes in 210 BCE. In 209 BCE, the conscription officers Chen Sheng and Wu Guang, leading 900 conscripts through the rain, failed to meet an arrival deadline; the Twenty-Four Histories claim that the Qin punishment for this delay would have been execution. To avoid this, Chen and Wu started a rebellion against Qin, known as the Dazexiang uprising, but they were thwarted by the Qin general Zhang Han in 208 BCE; both Wu and Chen were subsequently assassinated by their own soldiers. Yet by this point others had rebelled, among them Xiang Yu and his uncle Xiang Liang, men from a leading family of the Chu aristocracy. They were joined by Liu Bang, a man of peasant origin and supervisor of convicts in Pei County. Mi Xin, grandson of King Huai I of Chu, was declared King Huai II of Chu at his powerbase of Pengcheng with the support of the Xiangs, while other kingdoms soon formed in opposition to Qin. Despite this, in 208 BCE Xiang Liang was killed in a battle with Zhang Han, who subsequently attacked Zhao Xie the King of Zhao at his capital of Handan, forcing him to flee to Julu, which Zhang put under siege. However, the new kingdoms of Chu, Yan, and Qi came to Zhao's aid; Xiang Yu defeated Zhang at Julu and in 207 BCE forced Zhang to surrender.
While Xiang was occupied at Julu, King Huai II sent Liu Bang to capture the Qin heartland of Guanzhong with an agreement that the first officer to capture this region would become its king. In late 207 BCE, the Qin ruler Ziying, who had claimed the reduced title of King of Qin, had his chief eunuch Zhao Gao killed after Zhao had orchestrated the deaths of Chancellor Li Si in 208 BCE and the second Qin emperor Qin Er Shi in 207. Liu Bang gained Ziying's submission and secured the Qin capital of Xianyang; persuaded by his chief advisor Zhang Liang not to let his soldiers loot the city, he instead sealed up its treasury.
Contention with Chu
The Twenty-Four Histories allege that when Xiang Yu arrived at Xianyang two months later in early 206 BCE, he looted it, burned it to the ground, and had Ziying executed. In that year, Xiang Yu offered King Huai II the title of Emperor Yi of Chu and sent him to a remote frontier where he was assassinated; Xiang Yu then assumed the title Hegemon-King of Western Chu and became the leader of a confederacy of 18 kingdoms. At the Feast at Hong Gate, Xiang Yu considered having Liu Bang assassinated, but Liu, realising that Xiang was considering killing him, escaped during the middle of the feast. In a slight towards Liu Bang, Xiang Yu carved Guanzhong into three kingdoms with former Qin general Zhang Han and two of his subordinates as kings; Liu Bang was granted the frontier Kingdom of Han in Hanzhong, where he would pose less of a political challenge to Xiang Yu.In the summer of 206 BCE, Liu Bang heard of Emperor Yi's fate and decided to rally some of the new kingdoms to oppose Xiang Yu, leading to a four-year war known as the Chu–Han Contention. Liu initially made a direct assault against Pengcheng and captured it while Xiang was battling another king who resisted him—Tian Guang the King of Qi—but his forces collapsed upon Xiang's return to Pengcheng; he was saved by a storm which delayed the arrival of Chu's troops, although his father Liu Zhijia and wife Lü Zhi were captured by Chu forces. Liu barely escaped another defeat at Xingyang, but Xiang was unable to pursue him because Liu Bang induced Ying Bu, the King of Huainan, to rebel against Xiang. After Liu occupied Chenggao along with a large Qin grain storage, Xiang threatened to kill Liu's father if he did not surrender, but Liu did not give in to Xiang's threats.
With Chenggao and his food supplies lost, and with Liu's general Han Xin having conquered Zhao and Qi to Chu's north, in 203 BCE, Xiang offered to release Liu's relatives from captivity and split China into political halves: the west would belong to Han and the east to Chu. Although Liu accepted the truce, it was short-lived, and in 202 BCE at Gaixia in modern Anhui, the Han forces forced Xiang to flee from his fortified camp in the early morning with only 800 cavalry, pursued by 5,000 Han cavalry. After several bouts of fighting, Xiang became surrounded at the banks of the Yangzi River, where he committed suicide. Liu took the title of emperor, and is known to posterity as Emperor Gaozu of Han.
Reign of Gaozu
Consolidation, precedents, and rivals
Emperor Gaozu initially made Luoyang his capital, butupon the remonstrance of the soldier Lou Jing and the general Zhang Liangconsented to move it to Chang'an due to concerns over natural defences, nearby supplies, and better access to supply routes. Following Qin precedent, Emperor Gaozu adopted the administrative model of a tripartite cabinet along with nine subordinate ministries. Despite Han statesmen's general condemnation of Qin's harsh methods and Legalist philosophy, the first Han law code compiled by Chancellor Xiao He in 200 BCE seems to have borrowed much from the structure and substance of the Qin code.File:Han jade burial suit.JPG|thumb|left|Beginning in the Han period, kings were interred in jade burial suit made of small pieces of jade sewn together with golden thread.
After Xiao He completed construction of the Changle Palace in 200 BC, Emperor Gaozu removed his court to Chang'an. Its city walls would not be completed for another decade but he provided for the area's defense by forcibly relocating 100,000 descendants of the former Zhou aristocracy to the Guanzhong Region. From Chang'an, Gaozu ruled directly over 13 commanderies in the western portion of the empire. In the eastern portion, he established 10 semi-autonomous kingdoms that he bestowed to his most prominent followers to placate them. Due to alleged acts of rebellion and even alliances with the Xiongnu—a northern nomadic people—by 196 BCE Gaozu had replaced nine of them with members of the royal family.
According to Michael Loewe, the administration of each kingdom was "a small-scale replica of the central government, with its chancellor, royal counsellor, and other functionaries." The kingdoms were to transmit census information and a portion of their taxes to the central government. Although they were responsible for maintaining an armed force, kings were not authorized to mobilize troops without explicit permission from the capital.
Wu Rui, King of Changsha, was the only remaining king not of the Liu clan. When Wu Rui's great-grandson Wu Zhu or Wu Chan died heirless in 157 BCE, Changsha was transformed into an imperial commandery and later a Liu family principality. South of Changsha, Gaozu sent Lu Jia as ambassador to the court of Zhao Tuo to acknowledge the latter's sovereignty over Nanyue.