A strange invitation from a Roman princess gave him a pretext for the war, and threw an air of chivalric enterprise over his invasion. Honoria, sister of Valentinian III, the emperor of the West, had sent to Attila to offer him her hand and her supposed right to share in the imperial power. This had been discovered by the Romans, and Honoria had been forthwith closely imprisoned. Attila now pretended to take up arms in behalf of his self-promised bride, and proclaimed that he was about to march to Rome to redress Honoria's wrongs. Ambition and spite against her brother must have been the sole motives that led the lady to woo the royal Hun; for Attila's face and person had all the natural ugliness of his race, and the description given of him by a Byzantine ambassador must have been well known in the imperial courts. Herbert has well versified the portrait drawn by Priscus of the great enemy of both Byzantium and Rome:
"Terrific was his semblance, in no mould Of beautiful proportion cast; his limbs Nothing exalted, but with sinews braced Of Chalybean temper, agile, lithe, And swifter than the roe; his ample chest Was overbrow'd by a gigantic head, With eyes keen, deeply sunk, and small, that gleam'd Strangely in wrath as though some spirit unclean Within that corporal tenement install'd Look'd from its windows, but with temper'd fire Beam'd mildly on the unresisting. Thin His beard and hoary; his flat nostrils crown'd A cicatrized, swart visage; but, withal, That questionable shape such glory wore That mortals quail'd beneath him."
Two chiefs of the Franks, who were then settled on the Lower Rhine, were at this period engaged in a feud with each other, and while one of them appealed to the Romans for aid, the other invoked the assistance and protection of the Huns. Attila thus obtained an ally whose coöperation secured for him the passage of the Rhine, and it was this circumstance which caused him to take a northward route from Hungary for his attack upon Gaul. The muster of the Hunnish hosts was swollen by warriors of every tribe that they had subjugated; nor is there any reason to suspect the old chroniclers of wilful exaggeration in estimating Attila's army as seven hundred thousand strong. Having crossed the Rhine probably a little below Coblentz, he defeated the king of the Burgundians, who endeavored to bar his progress. He then divided his vast forces into two armies, one of which marched northwest upon Tongres and Arras and the other cities of that part of France, while the main body, under Attila himself, advanced up the Moselle, and destroyed Besançon and other towns in the country of the Burgundians.