In Thionville, France, Holy Roman Emperor Charlemagne issued the Capitulary of Diedenhofen, which strictly regulated the military equipment of his empire. The edict legally mandated that any landowner wealthy enough to own twelve manses must possess a 'brunia' (a heavy iron mail shirt or scale coat) and a helmet. It went so far as to forbid the export of these premium armors to foreign enemies, recognizing that superior armor was the foundation of Carolingian military dominance.

This enforced standardization created the economic and martial framework that birthed the 'Chansons de geste' (Songs of Heroic Deeds). The classic epic 'The Song of Roland' draws directly upon this Carolingian reality, filled with poetic references to white, bright brunias and iron helmets glinting in the sun.