حبیب السیر 15: The Conquest of 'Irāk.

15

Sultán Mahmúd, in the year 420 H. (1029 A.D.), formed the design of subduing 'Irák-i 'Ajam, and accordingly hoisted the standard of departure towards that quarter. When he arrived in the territories of Mázandarān, Manúchihr bin Kábús bin Washmíchihr having hastened to pay him his respects, brought fitting magnificent presents. In the mean time the governor of 'Irák, Majdu-d daula bin Fakhru-d daula, having sent a messenger to Yamínu-d daula, brought a complaint against his amírs. The Sultán having sent his troops towards Re, Majdu-d daula joined himself to the army of Ghaznín, and the officers of that army took him and sent him to the Sultán.
Sultán Mahmúd himself went to Re, and having sent for Majdu-d daula into his assembly, thus addressed him: — "Have you read the Sháh-náma, and are you versed in the history of Tabarí?" He answered, "Yes." The Sultán said: "Have you ever played at chess?" He answered, "Yes." The Sultán said: "In those books have you seen it written that two kings can rule in one country? and on the chess-board have you ever seen two kings on one square?" He said, "No." The Sultan said: "Then how comes it that you have given over the reins of your power to one who has greater strength than yourself?" He then sent Majdu-d daula and his son to Ghaznin, under the custody of a guard of soldiers, and having given over the sovereignty of that country to his son Mas'ud, he turned his reins towards the royal residence of Ghaznin.