That Victory everywhere followed the Presence of the Standard of the Cross in Battle
Indeed, wherever this appeared, the enemy soon fled before his victorious troops. And the emperor perceiving this, whenever he saw any part of his forces hard pressed, gave orders that the salutary trophy should be moved in that direction, like some triumphant charm against disasters: at which the combatants were divinely inspired, as it were, with fresh strength and courage, and immediate victory was the result.
Source: Life of Constantine (New Advent)