Sheikh Umar directed his disciple Baha-ud-din Zakariya to make Multan in present-day Pakistan the centre of his activity; and similarly his other disciple Syed Jalaluddin Surkh-Posh Bukhari made Uch his headquarters. Iltutmish appointed him "Sheikh ul-Islam" after the invasion of Multan and the overthrow of its ruler Nasir-ud-Din Qabacha. During the Mongol invasion he became the peace negotiator between the invaders and the Muslim army. Bukhari, known as "Makhdum Jahaniyan Jahangasht", the world traveller, was a puritan who strongly objected to Hindu influence on Muslim social practices.