Islam, The Byzantine Empire, and Germanic Tribes

Islam
Muhammad began his ministry at the age of 40, when, he claimed,
the archangel Gabriel appeared to him in a vision. Muhammad told only his
family and close friends about this and about all the other succeeding
visions. After four years he had converted at least 40 people to his views,
and he then began to preach openly in his native city of Mecca. Ridiculed
by the Meccans, he went in 622 to Medina. It is from this event, the Hegira
that the Islamic calendar is dated. At Medina, Muhammad soon held both
temporal and spiritual authority, having been recognized as a lawgiver and
prophet.…