The first Arab invasion of India was an expedition by sea to conquer Tana near Mumbai as early as 636 A.D. It was undertaken during the vigorous expansionist regime of the second Caliph, Umar-bin-Akhtab, who was on a proselytizing mission to spread Islam to all corners of the world. He appointed Usman, of the tribe of Sakif, to capture Bahrain and Oman. Usman sent his brother Hakam to Bahrain and himself proceeded to Oman. Upon reaching Oman, Usman sent a naval expedition to capture Thana on the western coast of India.