At the Battle of the Milvian Bridge outside Rome, Italy, soldiers under Constantine the Great deployed a new style of head protection: the late Roman ridge helmet. Unlike earlier one-piece helmets, the ridge helmet was constructed by joining two separate bowl halves with a central longitudinal metal ridge. This design was much easier to mass-produce in state fabricae and featured deep, secure cheek-pieces and neck guards attached by flexible leather thongs, providing practical protection during civil wars.

Constantine's victory while using these helmets altered the course of Christian history and literature. The event inspired Lactantius and subsequent Christian poets to write epic verses framing the military kit of Constantine's legions as the armor of God, merging pagan martial tropes with Christian theology.