When the Seljuq leader Tughril and his brother Chaghri began raising an army, they were seen as a threat to the Ghaznavid territories. Following the looting of border cities by Seljuq raids, Sultan Mas'ud I (son of Mahmud of Ghazni) decided to expel Seljuks from his territories.
During the march of Mas'ud's army to Sarakhs, the Seljuq raiders harassed the Ghaznavid army with hit-and-run tactics. Swift and mobile Turkmens were better fit to fight battles in the steppes and deserts than was the conservative heavily-laden army of Ghaznavid Turks. Seljuq Turkmens also destroyed the Ghaznavids' supply lines and so cut them off the nearby water wells. This seriously reduced the discipline and the morale of the Ghaznavid army. On May 23, 1040, around 16,000 Seljuk soldiers engaged in battle against a starving and demoralised Ghaznavid army in Dandanaqan and defeated them near the city of Merv destroying a large part of the Ghazanavid forces.[6] The Seljuks occupied Nishapur, Herat, and besieged Balkh.