Then Ali finally got his turn as caliph, but his ascension was very controversial and it ultimately led to a civil war, which eventually led to the emergence of Uthman's tribe, the Umayyads, as the dynasty that would rule over an ever-expanding Islamic empire for more than a hundred years. It's common to hear that in these early years Islam, quote, spread by the sword, and that's partly true, unless you are, wait for it, the Mongols. Actually, as usual, the truth is more complicated. Many people, including the Mongols, but also including lots of people in Central and East Asia, embraced Islam without any military campaigns. And in fact, the Quran says that religion must not be an act of compulsion, but this much is true. The early Islamic empire was really good at winning wars. And situated, as they were, between two very wealthy empires, the Byzantines and the Sassanians, there was plenty to fight for.