Explanation: In the aptly named Crisis of the Third Century, the Roman Empire was on the verge of literal disintegration. The frontier province of Illyricum (the modern day Balkans), combining both a high degree of assimilation into Roman culture and a pre-existing warrior society, provided a great many recruits for the Roman military, including several so-called 'barracks emperors' with military backgrounds.
They were not ready to give up on the dream that was ROME!