Muhammad, now ailing, orders a large expedition to be prepared against the empire of Constantinople in about the middle of May 632; three thousand Muslims are to join it.

Usama ibn Zaid, a young man and son of Zayd ibn Harithah, is appointed as commander of this force.

Muhammad falls ill a few months after his farewell pilgrimage to Mecca and dies on June 8 in the presence of Aisha, his third and favorite wife.

He is buried in Medina after the Muslim community elects her father, Muhammad’s closest advisor Abu Bakr, as Islam’s first caliph (“successor”; effectively, viceregent of the messenger of God), and pledges its allegiance, although Muhammad did not create this office or designate its authority.

He establishes the Rashidun Caliphate; it will last until 661.

Abu Bakr now launches a series of military campaigns against rebel Arabian tribes to establish the power of the Rightly Guided Caliphs and to secure Muhammad's legacy.

The rebels, who had submitted to Muhammad as the prophet of God, feel they owe nothing to Abu Bakr.

The army of Usama breaks camp and moves out on June 26, 632.

After leaving Medina, …