Iran! Particularly from the Mongols to the Qajars (1220-1925).

I used to be more interested in the Ottomans and particularly the Byzantines, but then I read Amin Maalouf's excellent novel Samarkand, and was entranced by its description of both medieval and modern(ish) Iran. The region has been at various points a crossroads of world trade, the cultural hegemon of the Islamic world, the bastion of heterodox religious fervour, the dominant centre of Shi'ism, a land that's prospered in spite of its terrible geography, and a land of constant contradictory oppositions: Turk vs Tajik, Nomads vs City-dwellers vs Agriculturalists, State vs Ulema/Bazaar/pretty much everyone, and more recently clerical rule vs secular rule. It's weird and wonderful and woefully understudied.

What has always particularly interested me is the early Safavid period (1501-1588), and the changes in the religious and political ideology of the state. The weird, heterodox mush that Islam turned into in the eastern part of the Middle East after the destruction of the Caliphate found its most extreme height in the initial rise to power of the Safavids, with this great wave of Sufi-Alid fanaticism raising up a ruler whose followers believed to be semi-divine, while indulging in huge propaganda efforts against the Ottomans and engaging in esoteric religious practices quite alien to the rest of the Islamic world (such as ritual cannibalism). But then Chaldiran happens, and the entire foundations of legitimacy are shaken, and there's this uncertain, fascinating period of ideological uncertainty, an increasing retreat into orthodox forms of piety and changing relations with the initial supporters who swept the dynasty into power in the first place.