List of emperors of the Han dynasty
The Han dynasty was founded by the peasant rebel leader (Liu Bang), known posthumously as Emperor Gao ("r". 202 –195 BC) or Gaodi. The longest reigning emperor of the dynasty was Emperor Wu ("r". 141–87 BC), or Wudi, who reigned for 54 years. The dynasty was briefly interrupted by the Xin dynasty of the former regent Wang Mang, but he was overthrown in 23 AD and the Han dynasty was reestablished by Liu Xiu, known posthumously as Emperor Guangwu (r. 25–57 AD), or Guangwu Di. The last Han emperor, Emperor Xian ("r". 189–220 AD), was a puppet monarch of Chancellor Cao Cao (155–220 AD), who dominated the court and was made King of Wei. In 220 AD, Cao's son Pi usurped the throne as Emperor Wen of Wei ("r". 220–226 AD) and ended the Han dynasty.
History of the Han dynasty
From 26–30 CE, Guangwu defeated various warlords and conquered the Central Plain and Shandong Peninsula in the east. Allying with the warlord Dou Rong (竇融) of the distant Hexi Corridor in 29 CE, Guangwu nearly defeated the Gansu warlord Wei Xiao (隗囂/隗嚣) in 32 CE, seizing Wei's domain in 33 CE. The last adversary standing was Gongsun Shu (公孫述), whose base was at Chengdu in modern Sichuan. Although Guangwu's forces successfully burned down Gongsun's fortified pontoon bridge stretching across the Yangzi River, Guangwu's commanding general Cen Peng (岑彭) was killed in 35 CE by an assassin sent by Gongsun Shu. Nevertheless, Han General Wu Han (d. 44 CE) resumed Cen's campaign along the Yangzi and Min rivers and destroyed Gongsun's forces by December 36 CE.
Since Chang'an is located west of Luoyang, the names Western Han (202 BCE – 9 CE) and Eastern Han (25–220 CE) are accepted by historians. Luoyang's 10 m (32 ft) tall eastern, western, and northern walls still stand today, although the southern wall was destroyed when the Luo River changed its course. Within its walls it had two prominent palaces, both of which existed during Western Han, but were expanded by Guangwu and his successors. While Eastern Han Luoyang is estimated to have held roughly 500,000 inhabitants, the first known census data for the whole of China, dated 2 CE, recorded a population of nearly 58 million. Comparing this to the census of 140 CE (when the total population was registered at roughly 48 million), there was a significant migratory shift of up to 10 million people from northern to southern China during Eastern Han, largely because of natural disasters and wars with nomadic groups in the north. Population size fluctuated according to periodically updated Eastern-Han censuses, but historian Sadao Nishijima notes that this does not reflect a dramatic loss of life, but rather government inability at times to register the entire populace.
Scrapping Wang Mang's denominations of currency, Emperor Guangwu reintroduced Western Han's standard five "shu" coin in 40 CE. Making up for lost revenue after the salt and iron monopolies were canceled, private manufacturers were heavily taxed while the government purchased its armies' swords and shields from private businesses. In 31 CE he allowed peasants to pay a military substitution tax to avoid conscription into the armed forces for a year of training and year of service; instead he built a volunteer force which lasted throughout Eastern Han. He also allowed peasants to avoid the one-month corvée duty with a commutable tax as hired labor became more popular. Wang Mang had demoted all Han marquesses to commoner status, yet Guangwu made an effort from 27 CE onwards to find their relatives and restore abolished marquessates.