I'm always fascinated by the idea that some political genius way back in the 4th century realised that the Roman Empire was doomed as a military empire, but cou

I'm always fascinated by the idea that some political genius way back in the 4th century realised that the Roman Empire was doomed as a military empire, but could survive as a church (of all things), and then managed to persuade everyone that this was a good idea and get it done. The Roman Empire changed its previous policy of wide tolerance regarding religion, adopted what had been a weird cult as the state religion, and survived its military annihilation (at least in the West - as you say, the story in the East is different).