Karim Khan Zand was an exceptional Persian ruler of the eighteenth century. Formerly an obscure Tribal chieftan, he came to power in the chaotic interregnum following the death of Nader Shah Afshar, a man celebrated for expelling the Afghan invaders from Iran but notorious for his subsequent tyranny. Karim Khan's moderate and innovative exercise of sovereignty (he refused the title of shah and ruled as vakil, "the People's Deputy"), and his skill in balancing the conflicting claims of pastoral nomad and urban magnate; of Persian, Turk and Arab; and of Shi'i, Sunni, Sufi, and non-Muslim, prompted a significant turn towards stability in the region. This comprehensive biography examines Karim Khan's time as leader and illustrates the evolution of Iran's unique identity among the emerging nations of western Asia. Arguing that Karim Khan's rule was the pivot in an era stretching from the 1500s, when the Safavid dynasty founded a kingdom with Imami Shi'ism as its official religion, to the revolt against the monarchy in 1979, this study provides an examination of the history of both Iran and one of its greatest leaders.