The Mamluks of the Ayyubid sultan Najm al-Din (637–47 / 1240–9) were trained in and stationed at barracks based at Roda Island on the river Nile. The Arabic word for a large river is al-bahr and this elite corps was, therefore, known as al-Bahriyya. After the death of the sultan one of the senior commanders, Baybars I al-Bunduqdari (r. 658–76 / 1260–77), turned the resulting power-vacuum to the Bahri Mamluks’ advantage and, after expelling the Mongols in 658 / 1260, emerged as the first great Mamluk sultan of an expanding empire. Bahri Mamluks now ruled until 784 / 1382, when they in turn had to yield power to another Mamluk faction, known as al-Burjiyya, named after the tower (al-burj) within the Citadel of Cairo that housed them.