The Mongol military centered on armies of decimally organized mobile horse archers. This system provided the Mongols with both a rationally organized military and a means of incorporating defeated enemies, as soldiers now belonged to units of a thousand rather than retaining old tribal identities. As the Mongol Empire expanded, new groups joined their ranks and the Mongols found new ways of accommodating them into their war machine without fundamentally disrupting their own ways of war. The Mongols also realized that regional needs sometimes dictated the use of other forces. Siege engineers, infantry, heavy cavalry, and naval forces all found use within the Mongol military. The Mongols showed flexibility not only in using personnel and military units, but also in adopting technologies, including gunpowder. After the dissolution of the United Mongol Empire, Mongol armies primarily fought each other in internecine wars. It became increasingly difficult to share training, technology, and personnel.

This chapter deals with various political, military, and social institutions that were rooted in the Mongols’ steppe tradition, which pre-dated the founding of their world empire. These institutions, which were continuously developed and modified by regional Chinggisid polities, also impacted post-Mongol empires. The chapter explains the formation and the transformation of the key concept of ulus (people, nation), and analyzes the composition and the maintenance of the ordo (mobile court) which was the geopolitical center of the ulus. It also analyzes military institutions, including decimal units, e.g., mingghan (chiliarchy) and tümen (myriarchy); the royal guards (keshig) and the garrisons (tamma); the main civil officials, such as the darughachi (governor) and jarghuchi (judge); and the postal system (jam). These topics only partially represent the wide variety of Mongol imperial institutions that still await extensive research, yet they offer a glimpse of how the Mongols ruled the world.

The emergence of a Mongol state in succession to the Kereyit khanate led to the creation of the largest land-based empire in history and a new people. The Mongols and their partners deployed and elaborated shared steppe political traditions that valued trade and customized the resources of both steppe and sedentary worlds. Under Chinggis Khan’s successor Ögödei, the mission of sacred world conquest and the ideology, governing mechanisms, and fiscal policies that enabled the attainment of this mission achieved sturdy articulation. Chinggisid priorities engendered massive demographic dislocation and transfers of peoples, and new patterns of commerce to support a robust imperial culture of consumption, patronage, and display. Early qa’ans’ ideological prerogatives and attempts to assert tighter control over resources inevitably clashed with their kinfolk’s customary claims. Tensions erupted into open civil war in 1260, but the new Chinggisid communicative space across Eurasia survived the breakup of the United Empire.