My understanding is that the emperor only allowed other peoples to come into the Empire in large numbers when they made deals with them, usually because they wa

My understanding is that the emperor only allowed other peoples to come into the Empire in large numbers when they made deals with them, usually because they wanted protection against a more ruthless enemy, while the Romans needed more men in their armies, so it was a win-win for both. I had never heard that people could just migrate into the Empire without hassle before, and the would be really surprising to me as it seems to contradict everything I've read about the time.