Reign of Selim I.

Driven by religious fanaticism, Selim I, the ninth Ottoman sultan, tried to eliminate Shī'ite resistance in eastern Anatolia beginning in 1513. He had some forty thousand heretics liquidated in the process, many of them partisans, envoys, or agents of the Persian ruler. Thereafter, Selim was engaged in a holy war against Persia’s shah Ismā'īl I, who had made Shiism the official form of Islam in his land east of the Ottoman borders. Ismā'īl, also, had sided with Selim’s brother, Ahmed, in their initial contest for power and given refuge to Ahmed’s son, Murad.