“Missionaries spreading Islam often accompanied traders with their faith.”  My world History (Early Ages)

“There is no mention in Islamic literature of any initiative undertaken by Muhammad and later caliphs of sending preachers (missionaries) to Persia, Egypt, and Byzantium.”  Islamic Jihad by M.A. Khan p.84

The author above also points out that in world history war and forced sexual propagation (rape) were the two major ways Islam spread through a conquered population. Not trade or voluntary conversion. Today, when Islam is in the minority in a country and cannot make war, the most violent form of spreading Islam is rape. So numerous, Norway had stopped counting Muslim gang rapes in their country.