The Mongol conquests took place during the 13th and 14th centuries, creating the largest contiguous empire in history, the Mongol Empire (1206–1368), which by 1260 covered a significant portion of Eurasia. At its height, it stretched from the Pacific to Central Europe. As the Mongol Empire began to fragment from 1260, conflict between the Mongols and Eastern European polities continued for centuries. Mongols continued to rule China into the 14th century under the Yuan dynasty, while Mongol rule in Persia persisted into the 15th century under the Timurid Empire. In the Indian subcontinent, the later Mughal Empire survived into the 19th century.
Background
The predecessors of the Mongol tribe were first recorded in the late tenth century, as they migrated from eastern Manchuria into the Mongolian Plateau, where they settled southeast of Lake Baikal near the mountain Burkhan Khaldun. During the twelfth century, the Mongols rose to prominence as its khans made allies and led raids on the Chinese Jin dynasty. The killing of the khans Qutula and Ambaghai in the 1160s ended this first confederation. The Mongols were reduced to comparative penury; other tribes, such as the Naimans in the west of the plateau and Kerait in the centre, became much more powerful, while the Mongols competed with smaller tribes like the Merkit and the Tatars, the allies of the Jin, in the east and north.
One nephew of Qutula Khan, named Yesugei, had some success fighting against the Tatars, and was a great friend of Toghrul, the khan of the Kerait. With his wife Hö'elün, whom he had abducted from her previous Merkit husband, Yesugei had several children, including a boy named Temüjin (the future Genghis Khan) who was born c. 1162.
Yesugei was poisoned by Tatars when Temüjin was still young and Hö'elün's family were abandoned by their tribe on the steppe. They survived the hostility of other tribes and the dangers of the steppe itself, while Temüjin killed his older half-brother to secure his familial position. As an adult, Temüjin formed alliances with Toghrul of the Kerait and an old friend named Jamukha who was now leader of his own tribe; they worked together to retrieve Temüjin's newlywed wife Börte, who had been kidnapped by Merkit raiders in retaliation for Hö'elün's abduction.
The victory over the Merkit brought Temüjin prestige and a considerable following; although he and Jamuqa initially remained close, their individual ambitions soon conflicted and turned hostile. In 1187, Jamukha decisively defeated Temüjin, who took refuge in China. Sponsored by the Jin, he returned to the steppe in 1196 and led a successful campaign with Toghrul against the Tatars in 1196, which re-established his prestige. Temüjin and Toghrul steadily increased their power over the next five years, culminating in a 1201 victory over a coalition led by Jamukha. In 1202, Temüjin eradicated the Tatars; this left the Mongols as the preeminent power in eastern Mongolia. Relations with Toghrul ruptured in 1203, but Temüjin managed to avoid defeat and subdued the Kerait. The Naimans were subjugated and Jamukha was executed in the next two years. With these victories, Temüjin became the undisputed ruler of a newly unified people—the Mongol Empire.
Military
The Mongol military eliminated the traditional weaknesses of nomadic armies and built upon their tactical strengths to become one of the most formidable armed forces in history. Previous nomadic armies were based on the skill of horse-archers—armoured cavalry able to shoot accurately and quickly with composite bows—who often overwhelmed their enemies with their speed and mobility, ambushes, or feigned retreats. However, their shortcomings included poor siege warfare capabilities, an inability to satisfactorily occupy defeated enemies, and above all a lack of military discipline, which often resulted in disunity or even, after a defeat, disintegration. The reforms initiated by Genghis Khan allowed the Mongol army to resolve these weaknesses, but their capabilities continued to evolve in response to new threats or opportunities to encompass, according to Christopher Atwood, "a vision of comprehensive warfare unique in the Middle Ages".
Focus and aims
To Genghis Khan, Atwood believes, "war was a personal vendetta against willfully defiant rulers" who had disrespected him or the Mongols. The broadening of these aims into a goal of world conquest was a gradual one; David Morgan argued that the Mongols "came round to the idea when they found that they were, in fact, conquering the world". The attractiveness of the idea was enhanced by the Mongol army's continuous success. By the time of the rule of Güyük Khan (r. 1246–1248), as he stated to the papal envoy Carpini, it had developed into official ideology.
from the rising of the sun to its setting, all the lands have been made subject to me. Who could do this contrary to the command of God?
Soldiers, horses, and equipment
Every adult Mongol man was a soldier; when not called up, they resumed their traditional pastoralist way of life. They received no army pay save plunder, which was divided post-battle according to each soldier's contribution. Most were horse-archers, having learned to ride since childhood. The small Mongolian breed was strong, quiet, and particularly hardy—although usually not shod, one could travel 600 miles (970 km) in nine days. A Mongol soldier took on campaign, on average, five or six horses to ride on alternate days. Ill-treatment of horses, such as eating before tending to their needs, could be punishable by death.
The Mongol composite bow, made of wood and horn, had a normal range of around 325 metres (1,066 ft), but in favourable conditions it could reach 530 metres (1,740 ft). Mongol soldiers, who all had at least one bow, carried them alongside two or three quivers containing arrows. Most arrowheads were of usual shape and construction, but the Mongols also used special arrows which whistled, stunned, or pierced. A major drawback of the bow was that it could not be used in the rain or damp weather. The Mongols preferred to not engage in close combat with forces who would usually be superior in that aspect, but nevertheless carried a wide range of hand-to-hand weaponry, including lances, maces, axes, spears, or clubs. The majority of Mongol soldiers had little or no armour, wearing as little as a deel (heavy coat) with an undergarment of dog or goat skin, accompanied by thick felt boots and fur hats. Wealthier Mongols could afford lamellar armour, preferred to metal mail because of its easy manufacture and greater effectiveness against arrows. Conical helmets were usually made of iron. Shields were used by sentries or by dismounted cavalry. Soldiers also had to carry equipment, including their tents.
Organisation and preparation
To ensure the old tribal loyalties disappeared, Genghis Khan assigned the soldiers of each tribe to different units, divided using a decimal system, of his army. Another critical reform was the institution of strict military discipline across the whole army from general down to common soldier. Officers were responsible for the training and equipping of the men under their command; comrades in units were ordered to protect each other in battle; and individual soldiers were forbidden from fleeing or looting without permission. If any soldier or unit failed in their duties, they were liable to be punished, often with execution. Institutions such as the layout of army camps or the operation chain of command were standardised, and the role of the keshig (imperial guard) was centred to ensure it served as a military academy for future generals.
The cohesion and unity of the Mongol military was a much greater factor in their success than any numerical superiority— the total strength available in Genghis's lifetime was likely between only 50,000 and 75,000 soldiers, and Mongol armies were almost always outnumbered. Before the division of the empire, the army was divided into five formations: the regular army, the alginchin and tamma frontier troops, who served as scouts and nomadic garrisons respectively, the keshig, and the qara'ul/qaraghul, whose function is unclear but may have included guarding roads and the frontier. All soldiers received a distinctive haircut, the uniqueness of which discouraged desertion.
The Mongols were accustomed to rest in late spring and summer. Campaigns were planned at summer kurultai. Here, commanders were appointed and plans drawn up, often using military intelligence gathered from merchants or their own scouting networks. Mongol war plans balanced independent tactical thinking by commanders with a strict strategic timetable. This allowed coordinated movements between divisions hundreds of miles apart before they rendezvoused at pre-selected locations. Preparations would begin in autumn, and the campaign usually started in winter—unlike their enemies, the Mongols favoured fighting in cold weather.
Strategy and tactics
The Mongols usually planned a multi-pronged invasion, relying on their plans and scouting networks to allow individual columns to join with others. Moving armies were protected from surprise attacks by scouting screens which ranged tens or hundreds of kilometers around the main force. They preferred to provoke the enemy ruler into an initial battlefield confrontation in which Mongol combat skill would prove decisive, followed by the destruction of smaller strongholds, and then the capture of the enemy capital. This sequence cut off any hierarchical communication, encouraged refugees to flee to the capital, decreasing the inhabitants' morale and supplies, and allowed the Mongols to obtain labour and materials to attack the best-defended fortresses. Often the enemy ruler was intensively pursued to prevent any force rallying around him. Similarly, individual divisions would unpredictably attack individual strongholds before quickly withdrawing, preventing local lords from helping their neighbours.
Mongol military tactics exploited their mastery as horse archers, emphasised their mobility, flexibility, and organisation, and generally aimed for a decisive total victory. They included traditional steppe tactics such as ambushes or the famous feigned retreat, which often lasted days before the Mongols confronted their tired pursuers on their chosen battlefield. Other tactics included hit-and-run barrages which resembled the later European caracole, specialised formations which disrupted enemy troops, or an "arrow storm" tactic which used the principle of concentrated firepower against a kill zone. Encirclement tactics were practised during the nerge great hunts, during which the Mongols formed circles many kilometres wide which gradually contracted, herding animals towards the center; these hunts were sometimes used to extinguish guerilla resistance.
The Mongols were initially poor at siege warfare, only being able to conquer walls with the element of surprise. However, they quickly learnt to incorporate Muslim and Chinese siege engineers into their armies. These artillery experts were used, in addition to sieges, on the battlefield, in naval warfare, and in logistics. Their equipment included trebuchets, mangonels, exploding shells, flaming naphtha, and the world's earliest-known cannon, dating from the late 13th century; their tactics included sapping, night attacks, and diverted bodies of water. The Mongols heavily used prisoners of war as forced labour and human shields during sieges. The spread of the Mongol military played a key role in technological diffusion across Eurasia, such as the transmission of trebuchets to China and gunpowder warfare to Europe. Naval warfare was generally only practised by the successor state of the Yuan dynasty.
Mongol armies also utilised terror tactics, psychological warfare, and propaganda. The population of captured cities, aside from useful individuals such as craftsmen, were usually massacred. The Mongols encouraged news of these events to be exaggerated and spread as widely as possible, to terrify potential targets into surrendering before a costly siege. They exaggerated the size of their armies with rumours, dummies mounted on spare horses, or extra fires lit at night camps; they promoted rebellion in enemy territory; and they sought to pit potential rivals against each other. Several accounts record that Mongol shamans were believed to play pivotal roles in summoning rainstorms or snowstorms which hindered enemy forces.