How big of a threat was Attila the Hun? 

The Huns, led by Attila, were one of the most fearsome enemies the Roman empire ever faced. But, how much of a threat were they to the Romans?
The Huns, Kim
The Huns, Rome, & the Birth of Europe, Kim
Empires of the Silk Road, Beckwith
The Later Roman Empire, Mitchell
Empires & Barbarians, Heather