Nicene and Post-Nicene Fathers: Series II/Volume I/Constantine/The Life of Constantine/Book IV/Chapter 21

.&#8212;He orders the Sign of the Saviour&#8217;s Cross to be engraven on his Soldiers&#8217; Shields.

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.