The Rise of Christianity
In a small province of the Roman Empire, a Jewish preacher named Jesus gathered followers, was executed by the Roman authorities, and — his followers proclaimed — rose again. What began as a tiny sect spread through the empire's cities and trade routes over three centuries, appealing especially to the poor, the enslaved, and women, until it captured the empire itself.
A belief system rises, spreads, institutionalizes, and then schisms — changing the rules people accept as legitimate.