Jews expelled from Palestine by the Romans in 135 settle Yathrib (the future Medina, or in Arabic, Al-Madinah) on the western edge of a large lava field along the eastern slope of the Hejaz mountain range, about three hundred miles (four hundred and eighty-five kilometers) north of present Mecca and one hundred and twenty miles (one hundred and ninety-three kilometers kilometers) northeast of the Red Sea.

Yathrib is supposedly the final resting place of Aaron, brother of Moses and High Priest of the Hebrews.

Jews are an important part not only of the Yemeni population, but also of the oases communities in the region of Medina.

Muhammad, in leaving Mecca, has chosen to abandon the city where he had grown up to pursue his mission in another place; thus, the event often has been used to illustrate a genuine commitment to duty and sacrifice.

This emigration, or hijra, marks the beginning of the Islamic calendar.

Muslims use a lunar calendar, which means that their twelve-month year is shorter than a solar one.

The Quraysh are unwilling to allow Muhammad to remain unopposed in Yathrib, and various skirmishes and battles occur, with each side trying to enlist the tribes of the peninsula in its campaigns.

Muhammad eventually prevails, and in 630 he returns to Mecca, where he is accepted without resistance.

Subsequently he moves south to strongholds in At Taif and Khaybar, which surrender to him after lengthy sieges.

Muhammad enjoys the loyalty of almost all of Arabia by his death in 632.

The Prophet has no spiritual successor inasmuch as God's revelation (the Quran) had been given only to Muhammad.

There are, however, successors to the Prophet's temporal authority, and they are called caliphs (successors or vice regents).

Caliphs will rule the Islamic world until 1258, when the last caliph and all his heirs are killed by the Mongols.

For the first thirty years, caliphs manage the growing Islamic empire from Yathrib, which has been renamed Madinat an Nabi ("the city of the Prophet") or Al Madinah al Munawwarah ("the illuminated city").

These names are usually shortened simply to Medina—"the city."

The caliphs have conquered a large empire within a short time.