Most enemies the Romans (they called themselves Romans through the final loss in 1453) that were strong enough to do threaten the aqueducts were on the other si

Most enemies the Romans (they called themselves Romans through the final loss in 1453) that were strong enough to do threaten the aqueducts were on the other side of the straits. The Roman navy was strong enough to prevent large scale assaults on the European side. Occasional disruptions occurred, but when they became more than occasional was when the city really stared to weaken.