One can read this article posted in The Quarterly Journal of Military History:
http://eserver.org/history/attila-at-chalons.txt
Some notes:
1. AtiLla invaded Gaul after massive preparations. So it was not an ordinary attack-and-retreat invasion.
2. Atilla had all opportunities to form a great army with enormous food supplies. Several years earlier he got money from East Roman Empire - A LOT OF MONEY.
3. In this article it is explained the hunnic warfare. They left nothing behind them, getting all they could get: food, armour, horses etc.
4. The backbone of Atilla's army were germans and goths. As for the ostrogoths it is widely known that they lived on a huge territory of modern Russia, Ucraine and to the east up to Ural mountains. Their population was also very big - enough big comparing to the numbers of combatants on Catalaunian plains.
