Early Islamic polity was intensely expansionist, fueled both by fervor for the faith and by economic and social factors. After gaining control of Arabia and the Persian Gulf region, conquering armies swept out of the peninsula, spreading Islam. By the end of the eighth century, Islamic armies had reached far into North Africa and eastward and northward into Asia.

Traditional accounts of the conversion of tribes in the gulf are probably more legend than history. Stories about the Bani Abd al Qais tribe that controlled the eastern coast of Arabia as well as Bahrain when the tribe converted to Islam indicate that its members were traders having close contacts with Christian communities in Mesopotamia. Such contacts may have introduced the tribe to the ideal of one God and so prepared it to accept the Prophet's message.

The Arabs of Oman also figure prominently among the early converts to Islam. According to tradition, the Prophet sent one of his military leaders to Oman to convert not only the Arab inhabitants, some of whom were Christian, but also the Persian garrison, which was Zoroastrian. The Arabs accepted Islam, but the Persians did not. It was partly the zeal of the newly converted Arabs that inspired them to expel the Persians from Oman.

Although Muhammad had enjoined the Muslim community to convert the infidel, he had also recognized the special status of the "people of the book," Jews and Christians, whose scriptures he considered revelations of God's word and which contributed in some measure to Islam. By accepting the status of dhimmis (tolerated subject people), Jews and Christians could live in their own communities, practice their own religious laws, and be exempt from military service. However, they were obliged to refrain from proselytizing among Muslims, to recognize Muslim authority, and to pay additional taxes. In addition, they were denied certain political rights.

Data as of January 1993