 Ghiyasuddin Iwaj Shah, the ruler of Bengal defeated by Iltutmish's forces, had earlier assumed the title "Nasir Amir al-Mu'minin", but he did so unilaterally without the Caliph's sanction.The Caliph probably saw Iltutmish as an ally against his Khwarazmian rival, which may have prompted him to recognize Iltutmish's authority in India.After the Caliph's recognition, Iltutmish began inscribing the Caliph's name on his coins, including the new silver "tanka" introduced by him.