: The army moved from a civic body of citizen-soldiers to a professional force increasingly reliant on foreign volunteers and foederati (allies).

: It wasn't all negative; barbarian recruits brought technological and tactical innovations, including new armor designs and horse-archery techniques adopted from steppe cultures. 2. The Cultural Myth vs. Reality

Here is a structured overview of what a high-quality post on the topic usually covers: 1. The Military Shift: From Citizens to Mercenaries

The most common focus is the "barbarization of the army." As the Roman Empire expanded and faced internal crises, it struggled to recruit enough Italian-born citizens.