In the autumn of 1240, a holy man hangs from the walls of a fortress above the Anatolian town of Amasya, and the army that has come to rescue him refuses to believe he is dead. His followers say he has ridden into heaven on a gray horse and will return. Then they destroy the sultan's army. The Babai Revolt was the greatest popular uprising in the history of Seljuk Anatolia. Led by the Khorasani mystic Baba Ilyas and his fiery deputy Baba Ishak, Turkoman herdsmen, dervishes, and the rural poor rose against a Persian-speaking court that taxed them into ruin. They shattered provincial armies, took Sivas and Tokat, and marched on the capital before Frankish knights broke them on the plain of Malya. The sultan survived. His kingdom did not. Within three years the Mongols had crushed the Seljuks at Köse Dä, while the scattered survivors of the rebellion carried their faith into the mountains and frontiers, where it helped shape the Ottoman state, the Bektashi order, and the Alevi communities of modern Turkey. Drawing on court chronicles, Syriac and Latin witnesses, and a rediscovered family hagiography, MacManus reconstructs a forgotten revolution of faith and grass. It is the story of how the defeated won.