Since Činggis Qan’s unification of various peoples on the Mongolian plateau in 1206, the Mongols quickly became a formidable force across Eurasia. After the death of Činggis Qan, the successors of the conqueror kept expanding their influence in China and Central and Western Asia. At the same time, the tensions among the Činggisid princes increased due to succession crises and competition over resources, until the Mongol Empire dissolved into several independent polities in the 1260s. In this process, how did the Činggisid rulers coordinate the imperials, officials, and subjects of diverse backgrounds across Eurasia? When the empire ceased to function as a unitary polity in the 1260s, was there a notion of unity still connecting the “independent” Činggisid khanates? By studying the military, economic and social networks established among the Činggisid houses in different parts of the Mongol Empire, this dissertation provides a fresh look at the fragmentation and unity of the empire. The work depends on the close reading of historical documents that ranged from the Secret History of the Mongols, the official histories of the “successor states” such as the Yuan Shi (especially the treatises on economics and certain biographies), Juvaynī’s Tārīkh-i Jahāngushāy and Rashīd al-Dīn’s Jāmiʻ al-Tawārīkh, essays of administrators who served the Mongols, to travelers’ accounts. Applying a holistic approach to the Mongol Empire, the work inquires the eastern and western domains of the Mongol Empire in a cohesive historical unit. By investigating the tradition of resource sharing presented in ulus division, military cooperation system such as the tamma, and administrative institutions aimed to distribute taxation incomes, the study demonstrates the significance of the post-Činggisqanid administrative policies that, despite their shortcomings, accommodated the steppe tradition of sharing resources and the bureaucratic efficiency within an expanding empire. When the political integrity of the Mongol Empire was impaired by civil wars and other imperial struggles in the 1260s, the socio-economic networks that connected the different Činggisid houses and uluses remained in place for much longer.