Late Roman army divided into regular units and federates in 5th century

February 28, 2026Theory

Source: Did the Roman Empire fall because it recruited too many barbarians into the military? by The Historian's Craft

The late Roman army had regular units and foederati drawn from non‑Roman sources. Foederati served for specific campaigns or were settled as laeti into permanent units. Some scholars argue that limitanei in the 5th century preferred to stay in their garrison areas. Generals such as Constantius and Aetius relied heavily on confederate troops, including Hunnic contingents. Their forces included bucellarii—private military followings kept by generals and high officials—alongside foederati under treaty obligations. Despite reliance on barbarian troops, the Western Roman army remained effective in many engagements.

Key facts

The late Roman army was divided into regular military units and federates drawn from non-Roman sources
Federates served for specific campaigns or were incorporated through laetitio into permanent units
The Lieuitz thesis argues regular army units in the 400s refused to operate outside their garrison areas
Generals Constantius and Aetius in the 5th century relied heavily on confederate troops
Bucellarii were private military followings maintained by generals and bureaucrats
Aetius specifically had a contingent of Huns in his personal following
The Western Roman army won most engagements between 400-450 AD
The rise of bucellarii, not barbarian recruitment, made rebellions more complicated