in Ṣafar 576 AH,¹ and his brother, King ʿIzz al-Dīn Masʿūd, assumed control of Mosul.
12 – The Khwārazmshāh Arslān ibn Atsiz ibn Muḥammad ibn Nushtekin
Sultan Arslān, son of the Khwārazmshāh (2) Atsiz (3), son of the amir Muḥammad ibn Nushtekin (4), inherited the throne after his father.
Their grandfather Nushtekin had been a mamluk in a private household until he was purchased by a Seljuk emir named Bilqā Beg. Nushtekin grew into an upright and intelligent man. A son, Muḥammad, was born to him; he devoted the boy to scholarship and literature, and Muḥammad matured into a complete and distinguished nobleman. He rose to prominence, assumed command, and, sometime around 500 AH, served as governor in Khwārazm. There he received the title Khwārazmshāh. He ruled justly, administered affairs with skill, honoured the scholars, and gained great standing with his liege lord, Sultan Sanjar. When he died, his son Atsiz Khwārazmshāh succeeded him; after Atsiz came his sons, until this Arslān took power, ranking among the great monarchs just as his father had.
Arslān returned from campaigning against the Khitā gravely ill and died in 568 AH. He was succeeded by his son Sulṭān Shāh Maḥmūd. Another son, Tekish, was then residing in the city of Jand; when news reached him, he bristled at the enthronement of his younger brother and marched to claim the kingdom.