Among the Mongols, and many other nomadic societies as well, all the able-bodied, adult males of the tribe bore arms: they constituted the armed forces when the occasion demanded. The unification of the different Mongol tribes and subsequent campaigns against diverse people introduced new members into Genghis Khan’s army complicating the composition of this relatively small, undifferentiated body into an incredibly heterogeneous mass of people. It included groups like the Turkic Uighurs, who had accepted his authority willingly. It also included defeated people, like the Kereyits, who were accommodated in the confederacy despite their earlier hostility.

Genghis Khan worked to systematically erase the old tribal identities of the different groups who joined his confederacy. His army was organised according to the old steppe system of decimal units: in divisions of 10s, 100s, 1,000s and [notionally] 10,000 soldiers. In the old system the clan and the tribe would have coexisted within the decimal units. Genghis Khan stopped this practice. He divided the old tribal groupings and distributed their members into new military units. Any individual who tried to move from his/her allotted group without permission received harsh punishment. The largest unit of soldiers, approximating 10,000 soldiers (tuman) now included fragmented groups of people from a variety of different tribes and clans.

The new military contingents were required to serve under his four sons and specially chosen captains of his army units called noyans. Also important within the new realm were a band of followers who had served Genghis Khan loyally through grave adversity for many years. Genghis Khan publicly honoured some of these individuals as his ‘blood-brothers’ (anda); yet others, freemen of a humbler rank, were given special ranking as his bondsmen (naukar), a title that marked their close relationship with their master. This ranking did not preserve the rights of the old clan chieftains; the new aristocracy derived its status from a close relationship with the Great Khan of the Mongols.

Genghis Khan assigned the responsibility of governing the newly conquered people to his four sons. These comprised the four ulus, a term that did not originally mean fixed territories. Genghis Khan’s lifetime was still the age of rapid conquests and expanding domains, where frontiers were still extremely fluid. For example, the eldest son, Jochi, received the Russian steppes but the farthest extent of his territory, ulus, was indeterminate: it extended as far west as his horses could roam. The second son, Chaghatai, was given the Transoxianian steppe and lands north of the Pamir mountains adjacent to those of his brother. Presumably, these lands would shift as Jochi marched westward.

Genghis Khan had already fashioned a rapid courier system that connected the distant areas of his regime. Fresh mounts and despatch riders were placed in outposts at regularly spaced distances. For the maintenance of this communication system the Mongol nomads contributed a tenth of their herd – either horses or livestock – as provisions. This was called the qubcur tax, a levy that the nomads paid willingly for the multiple benefits that it brought.

The conquered people, however, hardly felt a sense of affinity with their new nomadic masters. During the campaigns in the first half of the thirteenth century, cities were destroyed, agricultural lands laid waste, trade and handicraft production disrupted. Tens of thousands of people – the exact figures are lost in the exaggerated reports of the time – were killed, even more enslaved. All classes of people, from the elites to the peasantry suffered.

Once the dust from the campaigns had settled, Europe and China were territorially linked. In the peace ushered in by Mongol conquest (Pax Mongolica) trade connections matured. Commerce and travel along the Silk Route reached its peak under the Mongols but, unlike before, the trade routes did not terminate in China. They continued north into Mongolia and to Karakorum, the heart of the new empire.