The military of the Han dynasty was the military apparatus of China from 202 BC to 220 AD, with a brief interregnum by the reign of Wang Mang and his Xin dynasty from 9 AD to 23 AD, followed by two years of civil war before the reestablishment of the Han dynasty. Han armies consisted primarily of infantry and cavalry, with minor use of chariots that became obsolete during the Western Han (202 BC – 9 AD). The Han naval forces included marines on tower ships built for inland riverine and lake battles rather than overseas ventures.
To the north along the eastern Eurasian Steppe, the Han dynasty fought against nomadic confederations such as the Xiongnu, Xianbei, and Wuhuan. To challenge these migratory peoples effectively, the Han Empire was compelled to develop, train, and supply large amounts of cavalry and mounted forces. The Han-Xiongnu Wars that began during the reign of Emperor Gaozu of Han reached a turning point during the reign of Emperor Wu of Han, whose forces pushed the rival Xiongnu westward with the conquest of the Gansu corridor and establishment of the Protectorate of the Western Regions over the Tarim Basin of Central Asia. Weapons such as the crossbow gave Han forces a slight advantage against armies that lacked them.
Organization
Recruitment and training
At the start of the Han dynasty, male commoners were liable for conscription starting from the age of 23 until the age of 56. The minimum age was lowered to 20 after 155 BC, briefly raised to 23 again during the reign of Emperor Zhao of Han (r. 87–74 BC), but returned to 20 afterwards. Some convicts could choose to commute their service by serving on the frontier. Conscripts trained for one year and then served for another year either on the frontier, in one of the provinces, or at the capital as guards. A relatively small minority of these conscripts would also have served in the cavalry division in the north, which was primarily composed of volunteers from families of superior status, or waterborne forces in the south. Conscripts were generally trained to arrange themselves in a formation five men deep, but actual practice on the battlefield could be flexible, with some commanders preferring ranks of up to 10 men deep. Implementation of daily best practices was also highly dependent on each commander, with some like Li Guang eschewing administrative details while Cheng Buzhi always kept his men in tight formations. After finishing their two years of service, the conscripts were discharged. During Western Han times, discharged conscripts could still be called up for training once a year, but this practice was discontinued after 30 AD.
Certain nobles were exempt from military conscription. Those of ranks four to eight did not have to perform service in their locality, and those of rank 9 and higher had full exemptions. During the Eastern Han period, commoners were allowed to commute military service by paying a scutage tax.
Professional and Semi-Professional Armies
During the reign of Emperor Wu of Han, the standing army was significantly increased to face the military challenges presented by the Xiongnu during the Han–Xiongnu Wars and other opponents during the Southward expansion of the Han Dynasty. The number of cavalry forces was also significantly increased. The Han military by this time mostly favored longer-serving professional and semi-professional troops over troops that were regularly rotated and retired after a short length of service:
Garrison troops and armies in the provinces and frontiers were often professional or semi-professional military colonists. These soldiers were stationed on the frontier and served in the military in return for a land allotment. This land was often in the frontier itself, and created a self-sustaining system where the soldiers and retired soldiers would be able to farm land that would produce the food that would feed their armies and local populace. The difference between military colonies and agricultural colonies was that the former provided regular military service as well as grain, whereas the latter only provided grain and/or taxes.
During the time of Emperor Wu of Han, people of low reputation and/or low economic class who were initially conscripted often stayed in the military as a way to advance their social and economic status. This included paroled convicts, pardoned criminals, juvenile delinquents, etc. This created another subclass of professional or semi-professional troops that numbered at least 150,000 soldiers by 97 BC, making them a considerable percentage of the 500,000 to 700,000 troops that made up the Han standing army:
The Northern Army was a professional, full-time military force responsible for guarding the outer perimeter of the capital since 180 BC. It originally consisted of eight regiments and around 8,000 troops, but was later reorganized from 31 to 39 AD into a smaller force of five regiments, around 4,200 troops. The five regiments were each commanded by a colonel: the colonel of garrison cavalry, the colonel of picked cavalry, the colonel of infantry, the colonel of Chang River, and the colonel of archers. A captain of the center inspected the Northern Army and their encampments.
The Southern Army was established in 138 BC, consisting of 6,000 troops, to defend the imperial palace.
In 188 AD, the Army of the Western Garden was created as a counterweight to the Northern Army.
The total number of soldiers protecting the capital in the Eastern Han, amounted to some 20,000 soldiers.
+ Command structure of the Northern Army in 39 AD Army (軍 jun) Inspector Commander Regiment (部 bu) Troops Northern Army (北軍 beijun) Captain of the center (北軍中候 beijun zhonghou) Colonel (校尉 xiaowei) Picked cavalry (越騎 yueji) 900 Colonel (校尉 xiaowei) Garrison cavalry (屯騎 tunji) 900 Colonel (校尉 xiaowei) Archers who shoot at sound (射聲 shesheng) 900 Colonel (校尉 xiaowei) Foot soldiers (步兵 bubing) 900 Colonel (校尉 xiaowei) Chang River (長水 changshui) 900
+ Other establishments and titles Title Function Troops Bearer of the gilded mace (執金吾 zhijinwu) Capital police 2,000 cavalrymen1,000 halberdiers Colonel of the city gates (城門校尉 chengmen xiaowei) Gate garrisons 2,000 Rapid as tigers (虎賁 huben) Hereditary guard 1,500 Feathered Forest (羽林 yulin) Recruits from the sons and grandsons of fallen soldiers 1,700
Officers Neither the Qin or Han armies had permanent generals or field commanders. They were chosen from court officials on an ad hoc basis and appointed directly by the emperor as the need arose. At times several generals were given control of expeditionary forces to prevent any one general from obtaining overwhelming power and rebelling. A general's stipends were equivalent or slightly below that of the Nine Ministers, but in the case of failure on campaign, a general could face very severe penalties such as execution. Smaller forces were led by a colonel (xiaowei)
+ Command structure of the Han army on campaign General (將軍 jiangjun) Lieutenant-general (偏將軍 pian jiangjun)Commandant (都尉 duwei) Colonel (校尉 xiaowei) Major (司馬 sima) Captain of the army (軍候 junhou) Platoon chief (屯長 tunzhang)
Logistics According to Zhao Chongguo who served in the first century BC, a force of 10,281 men required 27,363 hu of grain and 308 hu of salt each month, requiring a convoy of 1,500 carts for transport. One hu is 19.968 liters, meaning that each soldier required per month 51.9 liters of grain and 0.6 liters of salt. Another document at Juyan suggests 3.2 hu, or 63.8 liters, of grain.
Maintaining a massive standing army and launching military campaigns was very expensive for the government of the Han Dynasty. The Han Dynasty government under Emperor Wu of Han had to create new taxes, impose government monopolies over salt and iron, and sell aristocratic ranks in order to obtain sufficient funding because the existing sources of government revenues were insufficient:
Decline
When imperial authority collapsed after 189 AD, military governors reverted to relying upon their personal retainers as troops. Due to the ensuing chaos of the Three Kingdoms period, there was no need for conscription since displaced peoples voluntarily enlisted in the army for security reasons. The end of the Han dynasty system of recruitment eventually led to the rise of a hereditary military class by the beginning of the Jin dynasty (266–420).
Chariots and horses
Although the chariot started losing prominence around the late Warring States period, it remained in use into the Han era until the Xiongnu war of 133 BC when they proved too slow to catch up to an all cavalry force. However chariots were still used as defensive pieces several decades later.
The Han's cavalry forces were fairly limited at the beginning of the dynasty. Their only large scale horse breeding programs existed in cities along northwest China: Tianshui, Longxi, Anding, Beidi, Shang, and Xihe. Emperor Wen of Han (r. 180–157 BC) decreed that three men of age could be exempted from military service for each horse sent by the family to the government. Emperor Jing of Han (r. 157–141 BC) set up 36 government pastures in the northwest to breed horses for military use and sent 30,000 slaves to care for them. By the time Emperor Wu of Han (r. 9 March 141 BC – 29 March 87 BC) came to power, the Han government had control over herds of roughly 300,000 horses, which increased to over 450,000 under Emperor Wu's reign. On paper, the Han dynasty at its height was capable of fielding up to 300,000 horsemen, but was probably constrained by their immense upkeep. A cavalryman on average cost 87,000 cash, not including rations, while a regular soldier only 10,000 cash. The total expenditure of a 300,000 strong cavalry force would therefore have been around 2.18 times the entire government's annual revenue.
Single mounting stirrups were used, but full double stirrups didn't appear until the later Jin dynasty (266–420).
Armour Han armour was similar to the armour used by the Qin dynasty with some variations and improvements. Soldiers wore suits of lacquered rawhide, hardened leather, bronze, iron, or steel, and came in varieties such as scale and lamellar. Helmets came as rawhide or hardened leather caps that were sometimes supplemented by a layer of metal lamellar, or made of metals such as iron or steel. Some riders wore armour and carried shields and some horses were at least partially armored, but substantial cataphract-like armor with comprehensive armor covering the entire horse is not attested to in writing until the late 2nd century.
+ Han dynasty inventory list (13 BC) Item Inventory Imperial Heirloom Jia armour 142,701 34,265 Kai armour 63,324 Thigh armour 10,563 Iron thigh armour 256 Iron lamellar armour (sets/suits?) 587,299 Helmets 98,226 Horse armour 5,330 Shields 102,551
During the late 2nd century BC, the government created a monopoly on the ironworks, which may have caused a decrease in the quantity and quality of iron and armour. Bu Shi claimed that the resulting products were inferior because they were made to meet quotas rather than for practical use. These monopolies as debated in the Discourses on Salt and Iron were abolished by the beginning of the 1st century AD. By the late Eastern Han Dynasty, political corruption caused a decline in the discipline and efficiency of the administration, which in turn had a detrimental effect on the quality of weapons. During the decline of the Eastern Han Dynasty in 150 AD, Cui Shi made similar complaints about the issue of quality control in government production due to corruption: "...not long thereafter the overseers stopped being attentive, and the wrong men have been promoted by Imperial decree. Greedy officers fight over the materials, and shifty craftsmen cheat them... Iron [i.e. steel] is quenched in vinegar, making it brittle and easy to... [?] The suits of armour are too small and do not fit properly."