Why had Islam not spread into Asia Minor (western and central Turkey) by 850? When and why did Islam eventually spread into this part of Asia?

Islam failed to spread into Asia Minor because of the Byzantine Empire. Constantinople was an easily defended city and they had greek fire to destroy any navy that approached. It wasn't until later that the Byzantine Empire fell. Islam started spreading into part of Asia because of merchants and missionaries. There were no conquests, but the merchants carried their religion with them