The Romans were a decaying bunch, with not very much to boast about and a rotten empire that was divided in half, ruled by four weak emperors. The only thing that arrested its slide into ignominy was the character and action of an ambitious, military, pious man called Constantine, whom history would call The Great. He picked Rome up and dusted it off, built a new capital for the empire, and with one gesture established Christianity as the religion of the known world. Those bold moves forged a relationship between church and state that would last until the enlightenment...