The military history of the Tang dynasty encompasses the period of Chinese military activity from 618 to 907. The Tang dynasty and the preceding Sui dynasty share many similar trends and behaviors in terms of military tactics, strategy, and technology, so it can be viewed that the Tang continued the Sui tradition.
Organization
The system of recruitment that created the Tang dynasty's Twenty-four Armies, as was the case in the preceding Sui dynasty, came to be known as fubing, or "territorial soldiery". Fubing soldiers were originally recruits drawn from the old military households of previous dynasties. Unlike the mass conscription of the Han dynasty, these soldiers were promised tangible rewards such as exemption from taxes and labor for their families. Later on, these soldiers were formed into units presiding over a plot of land on which they would farm privately to support themselves. At its height under the Tang dynasty, some 600 units of fubing were maintained, each with 800 to 1,200 soldiers. Unlike the Sui dynasty when the fubing answered only to local administration, the Tang dynasty implemented a centralized Ministry of the Army to which fubing units were answerable to. Each unit was further subdivided into battalions of 200, platoons of 50, and squads of 10. They rotated in and out of the capital for guard duty and training depending on their distance to it. Those nearest to it served one month in five, those furthest from it, two months out of every eighteen. Some men were assigned to three year tours in frontier garrisons. Deployment of the fubing units was monopolized by the court through the use of bronze tallies with the names of each unit on them. Half of the tally was kept at the Credentials Office while the other half was kept at unit headquarters. Only when the two halves were joined could a unit be mobilized.
While the fubing was well suited to local conflicts and short term campaigns, its shortcomings became apparent in the late 7th century as protracted wars and the needs of permanent static defense took their toll. The initial benefits of entering the system wore off as more men died in wars in far off lands, never to return. The military structure was not suited to properly reward soldiers who performed meritorious service in battle. Many who were supposed to be rewarded and compensated were not. Families of dead soldiers were also not compensated properly, resulting in reduced morale, and widespread desertion as well as dereliction of duty. The geographical distribution of fubing units was highly unevenly distributed, with the northwestern part of the empire shouldering most of the burden, while two thirds of the empire contained not even one unit of fubing. With so many units concentrated in one region, the government found it difficult to find enough farm land for their soldiers, who also competed with regular farmers under the equal-field system.
The fubing system was gradually replaced with a standing army. First, frontier garrisons were taken over by permanent troops known as jian'er in 677. In 710, frontier forces were bolstered to withstand invasions without the help of levied troops. Nine frontier commands were established, each with their own defense army and military governor, the jiedushi. In 737, the court decided to replace irregular troops entirely with permanent soldiers, recruited from volunteers in the general population. The fubing system was abolished in 749. The shift to a permanent army resulted in a sevenfold increase in the defense budget, from two million strings of copper cash in 712 to twelve million in 742, and then fifteen million by 755.
By 742 the frontier had been organized into ten regional military commands. Nine were headed by jiedushi. The post of jiedushi was an imperial commissionership with authority over the military, public revenue, and state lands. In essence, it was a provincial governorship. One jiedushi eventually rebelled in 755, causing the An Lushan Rebellion. Despite its defeat in 763, the number of jiedushi proliferated in response to the rebellion and had increased to approximately 40 by the end of the rebellion. The Tang court failed to reign in the northeastern jiedushi, who were functionally independent warlords, in particular and the balance of power seesawed between the two forces until the Huang Chao rebellion from 874 to 884. The Tang dynasty then collapsed.
Army operation According to the Tongdian (Comprehensive Canons), an expeditionary army consisted of 20,000 men in seven divisions of 2,600 or 4,000 men. Only 14,000 were actual combat troops while the rest guarded the baggage train. Of those 14,000, there were 2,000 archers, 2,000 crossbowmen, 4,000 cavalry, and the rest regular foot soldiers. Twelve thousand men were to be provided with armour.
The basic operational tactical unit was a platoon of 50 men, fixed five ranks deep. It had five officers: commander, deputy, standard-bearer, and two color guards. For every six platoons, one guarded the baggage train. When the entire army was deployed, the troops were formed into two lines with cavalry at their flanks. Movements were communicated with drums and gongs. Drum beats to advance and gongs to halt. Directions came from five flags, each with a different color to indicate the five directions. When two flags were crossed, it signaled for the platoons to combine into a larger formation.
The Tang army also made use of scouts on campaign. A pair of scouts were sent out for each of the four directions at different distances. Two at five li, another two at ten li, and so on until they reached 30 li.
Military examination In 702, Wu Zetian introduced military examinations for the recruitment of military officers. Examinees were tested on their skill with the bow and arrow, cavalry lance, as well as physical strength and command "presence". The imperial military exams had very little effect on the composition of the officer corps. While local military exams were administered, the final decision came down to the military governors, whose personnel appointments were routinely approved by the court. For example, at the beginning of 755, An Lushan replaced 32 Han Chinese commanders with his own barbarian favorites without any repercussions.
Equipment
Cavalry By the Tang dynasty it was possible for armour to provide immense personal protection. Heavy cavalry played an important role in the Tang army during the wars following the Sui dynasty's collapse. In one instance Li Shimin's cousin, Li Daoxuan, was able to cut his way through the entire enemy mass of Xia soldiers and then cut his way back again, repeating the operation several times before the battle was won, at which point he had so many arrows sticking out of his armour that he looked like a "porcupine." In another battle between Li Shimin and Wang Shichong, Li and his entourage of 500 armoured cavalry were attacked by a light cavalry force led by Shan Xiongxin. Shan charged at Li directly but was intercepted by one of Li's generals, Yuchi Gong, who knocked Shan off his horse. Yuchi then led the armoured cavalry force and broke through the enemy army while Li rallied his forces and drove through Shan's light cavalry several times. The arrows and spears of Wang's forces had little effect on Tang heavy cavalry. The effective range of a composite bow against armoured troops in this era was considered to be around 75 to 100 yards.
Li Shimin's elite cavalry forces were known to have worn distinctive black "iron clad" armour, but heavy cavalry declined as Turkic influence became more prevalent and light cavalry became the dominant mode of mounted warfare. In contrast to the heavily armored cavalry of the Sui dynasty, the horsemen of the Tang are often described as "light cavalry" because only the rider was armored while the horse was not. Prior to the founding of the Tang, Emperor Gaozu of Tang selected 2000 of his mounted forces and gave them the training and equipment to fight like Turks. Tang expeditionary forces to Central Asia preferred a mixture of light and heavy Chinese horse archers. After the An Lushan rebellion of the mid 8th century and losing the northwestern pastures to the Tibetans, Chinese cavalry almost disappeared altogether as a relevant military force. Many southern horses were considered too small or frail to carry an armoured soldier.
Li Shimin's six horses are described in poetry:
The Turks sent 100 horses to Emperor Taizong of Tang at one point. He chose from them ten for his own personal use and named them: Frost Prancing White, Shining Snow Grizzle, Frozen Dew Grizzle, Suspended Light Grizzle, Wave Plunging Bay, Sunset Flying Roan, Lighting Darting Red, Flowing Gold Yellow, Soaring Unicorn Purple and Running Rainbow Red.
Infantry armour
Infantry armour became more common in the Tang era and roughly 60 percent of active soldiers were equipped with armour of some kind. Armour could be manufactured natively or captured as a result of war. For instance 10,000 suits of iron armour were captured during the Goguryeo–Tang War. In the early Tang period when the fubing system was still active, soldiers were supposed to supply themselves with clothing and weapons at the outset of a campaign. However, after the fubing system was replaced with permanent soldiers known as jian'er in the late 7th century, the Tang government began supplying them themselves. Armour and mounts, including pack animals, were supplied by the state through state funds, and thus considered state property. Private ownership of military equipment such as horse armour, long lances, and crossbows was prohibited. Possession was taken as intent of rebellion or treason. The army staff kept track of armour and weapons with detailed records of items issued. If a deficiency was discovered, the corresponding soldier was ordered to pay restitution. The state also provided clothing and rations for border garrisons and expeditionary armies. Soldiers not on active duty were expected to pay for themselves, although "professional" soldiers were given tax exemptions. Officers, however, were permanently employed.
Mail armour Mail was already known to the Chinese since they first encountered it in 384 CE when their allies in the nation of Kuchi arrived wearing "armor similar to chains". However they did not procure a suit of mail until 718 CE when Central Asians presented to the Tang emperor a coat of "link armour". Mail was never used in any significant numbers (typically belonging to high ranks and those who could afford it) and the dominant form of armour continued to be lamellar.
Mountain pattern armour
References to mountain pattern armour () appear as early as the Tang dynasty, but historical texts provide no explanation or diagram of how it actually worked. There are also no surviving examples of it. Everything that is known about mountain pattern armour comes from paintings and statues, typically of the Song and Ming periods. It is not unique to China and has been found in depictions in Korea, Vietnam, Japan, and even Thailand, but non-religious depictions are limited to only China, Korea, and Vietnam. Reconstruction projects of this type of armour have largely failed to produce good results.
The current theory is that this type of armour is made from a multitude of small pieces of iron or steel shaped like the Chinese character for the word "mountain" (山). The pieces are interlocked and riveted to a cloth or leather backing. It covers the torso, shoulders and thighs while remaining comfortable and flexible enough to allow movement. Also during this time, senior Chinese officers used mirror armour () to protect important body parts, while cloth, leather, lamellar, and/or Mountain pattern armor were used for other body parts. This overall design was called "shining armor" ().
Dao (saber)