Placidia’s greatest failure, indeed, was in the training and education of her children.  Valentinian was incapable and vicious, while Honoria, who had inherited much of the romantic temperament of her mother, was both unscrupulous and irresponsible.  Sent to Constantinople on account of an intrigue with her chamberlain, Honoria, bored by the ascetic life in which she found herself and furious at her virtual imprisonment, sent her ring to Attila and besought him to deliver her and make her his wife as Ataulfus had done Placidia her mother.  Though, it seems, the Hun disdained her, he made this appeal his excuse.  Within a year of the death of Theodosius and Placidia he decided that the way of least resistance lay westward.  If he were successful he could make his own terms, and, among his spoil, if he cared, should be the sister of the emperor.

At first it was Gaul that was to be plundered; but there, as we know, the wild beast was met by Aetius who defeated him at the battle of Chalons and thus saved the western provinces.  But that victory was not followed up.  Attila and his vast army were allowed to retreat; and though Gaul was saved, Italy lay at their mercy.  That was in 451.  Attila retreated into Pannonia, and prepared for a new raid in the following year.

He came, as Alaric had done, through the Julian Alps; and before spring had gone Aquileia was not, Concordia was utterly destroyed, Altinum became nothing.  Nor have these cities ever lived again; out of their ruin Venice sprang in the midst of the lagoons.  All the Cisalpine plain north of the Po was in Attila’s hands; Vicenza, Verona, Brescia, Bergamo, Pavia, even Milan opened their gates.  No defence was offered, they saved themselves alive.  And southward, over the Po, between the mountains and the sea, the gate which Ravenna held stood open wide.  Italy without defence lay at the mercy of the Asiatic invader.

Without defence!  Valentinian and his court were in Rome; no one armed and ready waited in impregnable Ravenna to break the Hun as with a hammer when he should venture to take the road through the narrow pass between the mountains and the sea.  The great defence was not to be held; the road, as once before, lay open and unguarded.  In this moment, one of the greatest crises in the history of Europe, suddenly, and without warning, the reality of that age, which had changed so imperceptibly, was revealed.  The material civilisation and defence of the empire were, at least as organised things, seen to be dead; its spiritual virility and splendour were about to be made manifest.

For it was not any emperor or great soldier at the head of an army that faced Attila by the Mincio on the Cisalpine plain and saved Italy, but an old and unarmed man, alone and defenceless.  Our saviour was pope Leo the Great; but above him, in the sky, the Hun perceived the mighty figures, overshadowing all that world, of S. Peter and S. Paul, and his eyes dazzled, he bowed his head.  “What,” he asked himself, “if I conquer like Alaric only to die as he did?” He yielded and consented to retreat, Italy was saved.  The new emperor, the true head and champion of the new civilisation that was to arise out of all this confusion, had declared himself.  It was the pope.