Chapter XXI: He Orders the Sign of the Cross to Be Engraven on His Soldiers’ Shields — The Life of the Blessed Emperor Constantine

And not only so, but he also caused the sign of the salutary trophy to be impressed on the very shields of his soldiers; and commanded that his embattled forces should be preceded in their march, not by golden images, as heretofore, but only by the standard of the cross.

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The Life Of The Blessed Emperor Constantine -Eusebius Pamphilus

Chapter XXIHe Orders the Sign of the Cross to Be Engraven on His Soldiers’ Shields

Chapter XXI
He Orders the Sign of the Cross to Be Engraven on His Soldiers’ Shields