I’ve seen loads of explanations about the conquests of the Byzantine and entire Sassanian empire by the Muslims, but it is still absolutely mental how they did it so quickly, especially given the fact that many didn’t convert to Islam in the first few centuries.

Arabs served in the militaries of these empires, and therefore were familiar with tactics. The two empires were exhausted from fighting each other. The Muslims were fairer to the conquered peoples than either empire, although I suppose Zoroastrians and Christians may have been worse off. There are loads of reports of conquered populations welcoming the Muslims.

My favourite thing about this period is conversion. It varies, obviously, but I think it is always important to remember that the modern conception of conversion as a spiritual awakening is not exactly comparable to what would have been cultural assimilation amongst Christians and Jews to the ‘superior’ Islamic culture and population