Thus, Muhammad of Ghor was succeeded by Ghiyath al-Din Mahmud in 1206, although most of his conquests in the Ganga Valley were in the grasp of his lieutenants – Qutb ud-Din Aibak, Taj al-Din Yildiz, Bahauddin Tughril, Nasir ad-Din Qabacha and Muhammad Bakhtiyar Khilji who barely consulted Ghiyath al-Din Mahmud in their affairs. Notwithstanding, they still paid him a minimal tribute. During his reign, Mahmud also officially grant "manumission" on Aibak and Yildiz. Thus, freed from the slavery and with investment of a "chatr" from Mahmud, Yildiz established himself as the king of Ghazna in 1206 and Aibak in Lahore (who declared independence in 1208) established the Delhi Sultanate. Historian Iqtidar Alam Khan though, doubted that Aibak styled himself as the "Sultan" as it is not attested by the numismatic evidences. Soon, Mahmud was enforced to accept suzerainty of Alauddin Shah of Khawarazm as attested by the numismatic evidences in which he minted his name along with placing Alauddin's name in the "khuṭbah" until his assassination in 1212.
