The great city-port thus became one of the most important and considerable of the cities of Italy, at a time when the whole of the West was rapidly increasing in wealth and population, and especially the old province of Cisapline Gaul, which had indeed become, during the _pax romana_, the richest part of the new Italy. Always an important military port it was often occupied by the emperors as their headquarters from which to watch and to oppose the advance of their enemies into Italy, and the possessor of it, for the reasons I have set forth, was always in a commanding position. Thus in A.D. 193 it was the surrender of Ravenna without resistance that gave the empire to Septimius Severus, when, scarcely allowing himself time for sleep or food, marching on foot and in complete armour, he crossed the Alps at the head of his columns to punish the wretched Didius Julianus and to avenge Pertinax. It was there in 238 that Pupienus was busy assembling his army to oppose Maximin when he received the news of the death of his enemy before Aquileia. And because it was impregnable and secluded it was often chosen too as a place of imprisonment for important prisoners. It is true that we know very little, in detail, of the life of any city other than Rome during those years of the great Peace in which we see the empire change from a Pagan to a Christian state. Those centuries which saw Christendom slowly emerge, in which Europe was founded, still lack a modern historian, and the magnitude and splendour of their achievement are too generally misconceived or ignored. We are largely unaware still of what they were in themselves and of what we owe to them. By reason of the miserable collapse of Europe, of Christendom, in the sixteenth century and its appalling results both in thought and in politics, we are led, too often by prejudices, to regard those mighty years rather as the prelude to the decline and fall of the empire than as the great and indestructible foundations of all that is still worth having in the world. For rightly understood those centuries gave us not only our culture, our civilisation, and our Faith, but ensured them to us that they should always endure. They established for ever the great lines upon which our art was to develop, to change, and yet not to suffer annihilation or barrenness. They established the supremacy of the idea, so that it might always renew our lives, our culture, and our polity, and that we might judge everything by it and fear neither revolution, defeat, nor decay. They, and they alone, established us in the secure possession of our own souls so that we alone in the world might develop from within, to change but never to die, and to be--yes, alone in the world--Christians.