The Fall of Rome podcast had a really interesting episode on The Huns: https://m.soundcloud.com/fallofromepodcast/fall-of-rome-epis...

He makes the argument that in the later Roman Empire, the Huns treated the Roman Empire as either a vassal or a buffer state to their own empire. They demanded tribute from them and even forced the romans to chase down and return refugees. It's really interesting to look at the Roman Empire from a hun-centered point of view-- just one more border state along a small section of a vast empire.

They seem to have been one of a long series of steppe empires with the same basic organization-- from the Scythians to the Mongols.