The Roman Empire Needed New Walls

Galienus had made sure that he was always at the head of the most massive army the empire could put together, complete with its totally dominant mobile cavalry. That meant wherever this great imperial army wasn't, well, that is where the germans would be. This meant an awful lot of rushing around trying to expel invaders after they had already invaded. What the empire needed was city walls on their own initiative. Aurelian now put the imperial stamp of approval on the idea of permanently fortified cities by ordering a massive wall circuit built around rome itself.