There were significant advances in science and technology during the Han period, including the emergence of papermaking, rudders for steering ships, negative numbers in mathematics, raised-relief maps, hydraulic-powered armillary spheres for astronomy, and seismometers that discerned the cardinal direction of distant earthquakes by use of inverted pendulums.

According to the Records of the Grand Historian, after the collapse of the Qin dynasty the hegemon Xiang Yu appointed Liu Bang as prince of the small fief of Hanzhong, named after its location on the Han River (in modern southwest Shaanxi).

The loyalty of non-relatives to the emperor was questioned,[13] and after several insurrections by Han kings—with the largest being the Rebellion of the Seven States in 154—the imperial court began enacting a series of reforms that limited the power of these kingdoms in 145, dividing their former territories into new commanderies under central control.

[30][31] However, a court conference the following year convinced the majority that a limited engagement at Mayi involving the assassination of the Chanyu would throw the Xiongnu realm into chaos and benefit the Han.

Zhang encountered Dayuan (Fergana), Kangju (Sogdiana), and Daxia (Bactria, formerly the Greco-Bactrian Kingdom); he also gathered information on Shendu (the Indus River valley) and Anxi (the Parthian Empire).

Guangwu made Luoyang his capital in 25 AD, and by 27 his officers Deng Yu and Feng Yi had forced the Red Eyebrows to surrender and executed their leaders for treason.

[95][96] During the turbulent reign of Wang Mang, China lost control over the Tarim Basin, which was conquered by the Northern Xiongnu in AD 63 and used as a base to invade the Hexi Corridor in Gansu.

[105][106] When a request by Kushan ruler Vima Kadphises (r. c. 90 – c. 100 AD– ) for a marriage alliance with the Han was rejected in AD 90, he sent his forces to Wakhan (modern-day Afghanistan) to attack Ban Chao.

[119][113] Óc Eo is also thought to be the port city "Cattigara" described by Ptolemy in his Geography (c. 150 AD) as lying east of the Golden Chersonese (Malay Peninsula) along the Magnus Sinus (i.e. the Gulf of Thailand and South China Sea), where a Greek sailor had visited.

[169] By the Eastern Han, local elites of unattached scholars, teachers, students, and government officials began to identify themselves as members of a nationwide gentry class with shared values and a commitment to mainstream scholarship.

[205] The early Western Han court simultaneously accepted the philosophical teachings of Legalism, Huang-Lao Taoism, and Confucianism in making state decisions and shaping government policy.

[245] Commonly eaten fruits and vegetables included chestnuts, pears, plums, peaches, melons, apricots, strawberries, red bayberries, jujubes, calabash, bamboo shoots, mustard plant, and taro.

[246] Domesticated animals that were also eaten included chickens, Mandarin ducks, geese, cows, sheep, pigs, camels, and dogs (various types were bred specifically for food, while most were used as pets).

[250][255] In addition to his many other roles, the emperor acted as the highest priest in the land who made sacrifices to Heaven, the main deities known as the Five Powers, and spirits of mountains and rivers known as shen.

[257][258][259][260] If the emperor did not behave according to proper ritual, ethics, and morals, he could disrupt the fine balance of these cosmological cycles and cause calamities such as earthquakes, floods, droughts, epidemics, and swarms of locusts.

6th century BC) was a holy prophet who would offer salvation and good health if his devout followers would confess their sins, ban the worship of unclean gods who accepted meat sacrifices, and chant sections of the Tao Te Ching.

[270][c] In Han government, the emperor was the supreme judge and lawgiver, the commander-in-chief of the armed forces and sole designator of official nominees appointed to the top posts in central and local administrations; those who earned a 600-bushel salary-rank or higher.

The Chancellor's other duties included managing provincial registers for land and population, leading court conferences, acting as judge in lawsuits, and recommending nominees for high office.

[298][299] The Minister Steward (Shaofu 少府) served the emperor exclusively, providing him with entertainment and amusements, proper food and clothing, medicine and physical care, valuables and equipment.

[301] He was the top civil and military leader of the commandery and handled defence, lawsuits, seasonal instructions to farmers, and recommendations of nominees for office sent annually to the capital in a quota system first established by Emperor Wu.

[310][311] A Magistrate maintained law and order in his county, registered the populace for taxation, mobilized commoners for annual corvée duties, repaired schools, and supervised public works.

The Han and Xiongnu now held one another out as the "two masters" with sole dominion over their respective peoples; they cemented this agreement with a marriage alliance (heqin), before eliminating the rebellious vassal kings in 154 BC.

[335] The widespread circulation of coin cash allowed successful merchants to invest money in land, empowering the very social class the government attempted to suppress through heavy commercial and property taxes.

[346][347] To eliminate the influence of such private entrepreneurs, Emperor Wu nationalized the salt and iron industries in 117 BC and allowed many of the former industrialists to become officials administering the state monopolies.

[377][378] To protect crops from wind and drought, the grain intendant Zhao Guo (趙過) created the alternating fields system (daitianfa 代田法) during Emperor Wu's reign.

[425][429] Zhang also invented a device he termed an "earthquake weathervane" (houfeng didong yi 候風地動儀), which the British sinologist and historian Joseph Needham described as "the ancestor of all seismographs".

[465] Although the use of graduated scales and grid references in maps was not thoroughly described prior to the work of Pei Xiu (AD 224–271), there is evidence that their use was introduced in the early 2nd century by the cartographer Zhang Heng.

[478] Han-era medical physicians believed that the human body was subject to the same forces of nature that governed the greater universe, namely the cosmological cycles of yin and yang and the five phases.

[482][483][484][485] When surgery was performed by the Chinese physician Hua Tuo (d. AD 208), he used anaesthesia to numb his patients' pain and prescribed a rubbing ointment that allegedly sped up the healing process for surgical wounds.

[482] The physician Zhang Zhongjing (c. 150 – c. 219 AD) is known to have written the Shanghan Lun ("Dissertation on Typhoid Fever"), and it is thought that he and Hua Tuo collaborated to compile the Shennong Bencaojing medical text.