I'm reading the wiki page on Attila, and this caught my eye
The Huns remained out of Roman sight for the next few years while they invaded the Sassanid Empire. They were defeated in Armenia by the Sassanids, abandoned their invasion, and turned their attentions back to Europe. In 440, they reappeared in force on the borders of the Roman Empire, attacking the merchants at the market on the north bank of the Danube that had been established by the treaty.
The only one I saw was in Gibbon's work, The Decline & Fall of The Roman Empire. There are other accounts, probably.
The Gibbon work relates that a Hunnic force passed what seemed to be the Sea of Azov (referred to as Lake Maeotis) and entered the Persian Empire, through the Caucasus region. The Huns were forced to retire from the Persian counter-attack.