The spread of Islam changed many countries. The religion quickly spread and many countries of power classified themselves as Muslim countries. This united the countries in a religious manner and all of the Muslim countries were led and ruled by a khalifah. The united rule helped Muslims achieve victory over battles that would change the face of the Earth.
I think a but its your choice
Tariff i believe --------------------
A lot of reasons while others were struggling with monarchy and oligarchy etc. they didn't want to and they did prefer independence.