Mongol Armies and Military Organisation

Between 1206 and the division of the empire around 1260, Mongol armies made mounted archers their core while drawing on soldiers, engineers and supplies from the lands they conquered. The mix changed by campaign. A force moving across open pasture could rely heavily on horsemen; an operation against fortified cities needed different equipment, specialists and labour. It functioned as a command system that could combine the people and equipment needed for each campaign.

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Turning followers into an imperial army

Before Temüjin was proclaimed Chinggis Khan in 1206, he reorganized his followers into a decimal command structure. Groups of ten, one hundred, one thousand and ten thousand gave officers a chain for issuing orders and assembling forces. The largest grouping, called a tümen, was nominally ten thousand. These names described units within a military and administrative system; they did not guarantee that each field force contained exactly the stated number of fighting men.

Chinggis Khan changed who commanded those units. Followers from formerly separate tribes were redistributed among new groupings, and commanders chosen for personal loyalty could replace older tribal chiefs. Some powerful lineages retained followers, but the restructuring placed a wider network of people under the ruling house. A unit could connect military service with the organization of households and resources, making it useful for mobilization as well as battlefield command.

The Secret History of the Mongols, a thirteenth-century chronicle, describes Mongol warriors learning to use spears and swords from childhood. The Franciscan envoy Giovanni da Pian del Carpine, who visited the Mongol court in 1246–47, also describes strict unit discipline: men in a group of ten were expected to move together, and his account says that fleeing separately, refusing to follow comrades into battle, or failing to rescue a captured comrade could bring execution. His examples connect training and harsh penalties to the formation’s ability to act together.

The ruler’s keshig was a cross-tribal royal guard: a personal retinue that protected the khan and served at court. Its members belonged to a privileged, close-service force rather than an ordinary campaign unit. The guard also became a route into imperial military and administrative service. This linked access to the ruler with the work of commanding an expanding army.

The mounted Mongol force was not the whole army. As conquests widened, commanders used submitted or recruited soldiers from other societies. Some could be incorporated into the decimal units; others retained their own formations and equipment because their skills suited different tasks. Commanders assigned incorporated troops tasks suited to their experience, including foot assaults, cavalry support and engineering. Effective command meant coordinating these forces while preserving the work each could do best.

Horses, bows and the work of movement

Mongol cavalry relied on the horse as transport and as part of its fighting equipment. The composite bow joined materials such as wood, horn and sinew into a compact weapon that a rider could use from horseback. Archers practiced drawing and releasing while moving; the bow gave a mounted unit the means to attack at a distance before a close engagement. Carpine says a warrior was expected to carry one good bow or several bows and three quivers of arrows, so ammunition traveled with the rider; he describes arrowheads honed on both edges. His account also lists battle-axes, hook-ended lances used to pull opponents from the saddle, and single-edged, slightly curved swords among wealthier men. He describes layered hide armor as well as overlapping iron plates, with separate protection for the body, legs, head and horse. Access to swords and heavier armor varied with a fighter’s means and role.

A saddle and stirrups helped a rider stay seated and steady while handling a bow. Saddlebags held practical provisions such as a cooking pot, dried meat, yogurt and water. Remounts let riders change horses on a long route, resting one animal while another carried the rider. That system required careful attention to the animals and access to pasture. The speed of a cavalry column still depended on water, grazing and the condition of its horses.

The communal hunt offered another setting for coordinated riding. In the nerge, riders formed a broad circle and gradually drove game toward its center. Hunting taught groups to keep their positions and close a moving perimeter; the same kind of coordination could help cavalry surround an opposing force. In battle, horse archers could spread out, shoot while moving and converge when an enemy formation began to break.

Feigned withdrawal turned that mobility into a deliberate maneuver. A unit could retreat in apparent disorder, encouraging pursuers to stretch their line and lose contact with supporting troops. The Mongols could then turn back or strike with another force. In the western expedition after the campaigns in Central Asia, Jebe and Sübedei’s troops used this pattern against Georgian cavalry: the pursuers were drawn out, while rested horses and hidden archers helped the Mongols return to the attack. Scouting supplied information for such timing. Carpine describes scouts riding ahead with horses, tents and weapons, followed by raiders sent to locate people and herds. Timothy May describes scouts screening Mongol columns and relaying reports, allowing commanders to track enemy positions while keeping separated columns able to join up. The information helped a commander choose where to move and when to concentrate troops.

When an army reached a wall

The wars in northern China brought Mongol forces against fortified cities and exposed the need for siegecraft. Mongol commanders recruited or captured people who knew how to build and operate siege engines. Chinese, Iranian and other specialists joined campaigns in different regions, while infantry and heavier cavalry performed work that mounted archers could not.

A siege engine was a large machine for throwing stones or other missiles against walls and defenders. Its frame and throwing arm had to be built, assembled and supplied; the equipment was difficult to move at the same pace as a cavalry column. Engineers, carpenters, transport animals and crews therefore formed a slower-moving part of an army. Commanders had to protect this equipment and bring it into position while mounted forces handled reconnaissance, screening and operations outside the walls.

At the battle of Mohi in Hungary in 1241, Mongol forces used trebuchets, large catapults, to bombard defenders at a bridge over the Sajó River and help seize the crossing. Here the engine supported a field operation rather than simply battering a city wall. In the 1250s, Möngke sent his brother Hülegü west into Iran against the Nizari Ismailis, a religious community whose leaders held fortified mountain strongholds. Taking these sites required siege engineers alongside cavalry.

Supplying campaigns across different landscapes

A force of horsemen needed more than weapons. Its animals consumed pasture, and riders had to carry food and water between supply points. In steppe country, herds and grazing could support movement, but a long campaign still required route planning and care of the mounts. In agricultural regions, armies could draw on stored grain, transport and local production. Those resources could sustain a force, but requisitions also shifted the burden of war onto conquered communities.

The invasion of Hungary in 1241–42 shows how supplies and terrain shaped operations. Büntgen and Di Cosmo note a report that the Mongols could not take marsh-surrounded Székesfehérvár as snow and ice thawed in early 1242; they argue that flooded ground and reduced pasture constrained cavalry movement. A later regional study by József Laszlovszky and colleagues argues that climate was not decisive and emphasizes local resistance and Mongol military failures. At a fortress, horses still needed forage and siege troops needed firm ground to approach; the campaign joined these logistical and military pressures.

Command under Chinggis Khan’s successors

Chinggis Khan established the command structure and expanded it through campaigns in the Western Xia kingdom and the Jin dynasty, two Chinese polities, then into Central Asia. Ögedei, Great Khan from 1229 to 1241, continued the war against Jin, whose conquest ended in 1234. Güyük ruled briefly from 1246 to 1248. Under Möngke, who became Great Khan in 1251, the empire organized campaigns in distant theatres: Hülegü moved west from 1255, while Qubilai campaigned in China. Each required forces shaped by local conditions, from cavalry on open routes to infantry and siege specialists near fortified targets.

Möngke’s death in 1259 brought rival claims to the supreme title and weakened common command. By about 1260, regional rulers increasingly directed their own campaigns and resources. That change marked the end of the united imperial army as the single subject of this account; the armies of the successor states developed in separate political settings.