In 1296 Alauddin became the sultan after Malika Jan the widow of Jalaluddin and her younger son Qadir Khan left Delhi. He also exterminated the old Balbani and Jalali nobles. The reign of Alauddin Khilji marks the zenith of the power of the Delhi Sultanate. In 1297 he set off for conquering Gujarat. He sent an expedition under Ulugh Khan and Nusrat Khan to Gujarat. On the way Ulugh Khan conquered Jaisalmer.
During the plunder of the rich port of Cambay Alauddin's commander Nusrat Khan acquired a Hindu turned Muslim slave Kafur who later on rose to become a great military general and the Malik Naib of Alauddin. After the conquest of Gujarat Alauddin sent an expedition under Ulugh Khan and Nusrat Khan to Ranthambhore. However they were beaten by the Rajputs and Nusrat Khan died. Alauddin went to Ranthambhor and annexed it in 1301. The next expedition was sent to Mewar and after the siege of 8 months he captured Chittor in 1303. The government of Chittor was put in the hands of Khizr Khan, the eldest son of Alauddin. Chittor was renamed as Khizrabad after the name of Khizr Khan. In 1305 Alauddin sent Ain-ul-Mulk Multani for the conquest of Malwa which was placed under the governorship of the latter. By the end of 1305 the whole of Northern India fell into the hands of Alauddin and he directed his attention to the conquest of Deccan.