With the advent of Turkish rule in north-western India in the early 11th century, Muslims began to settle in the region. To their increasing numbers were added the local converts. By the time of Guru Nanak (1469-1539), Muslims had become the most visible section of the social order in Punjab. They consisted mainly of the orthodox Sunnis, represented by the ulama (mullas and qazis) who upheld the Islamic law (shariat), and the various orders of the mystics of Islam (the Sufis) who represented a parallel interpretation of religious beliefs and practices. Guru Nanak came into close contact with Islam during his 10-year stay in Sultanpur, and later at several places during his travels. He brackets Islam with the major religious systems of India in the early 16th century.