In The Ancient Roman Army (Legions), the term ''Numerus'' was associated with Barbarian Allies – who fought with Rome. These were most often found in far flung Colonies and Provinces. In many cases, various Tribes (who were Allied), were in ''Blood Feuds'' with rivals Tribes, would easily align and fight ''with Rome''. In most cases though, after a rival Tribe was destroyed, they would ''turn against'' their Roman Allies.
Rome classed these Numerus into States known as ''Foederati''. In addition to supplying Forces, these Tribal Kingdoms would be given various Roman ''courtesies''. This might bye trade concerns, monies or even being Overlords of subjugated Nations (Rival Tribes).
Often given very basic often outdated Roman equipment, The Numerus would none the less still be used into the 3rd Century AD. Some examples were The Huns, Alans and Visigoths.