Muslim merchants migrated east to the land of Tang, Changan and other Chinese cities, Some merchants returned to their lands but others remained in those lands with the Tang emperor's permission and also allowed them to marry Chinese women. In Islam, Muslim children were also Muslims and the religion in the East rose.
Try reading the first paragraph of this. It may help. https://books.google.com/books?id=IQwAAAAAMBAJ&pg=PA2&lpg=PA2&dq=How+does+columbus+and+smith+deploy+...