[ by Charles Cameron — vexilla regis prodeunt, comparative versions ]
Two recent examples of religious iconography on the battle field.. from the Badr Brigade, outside Amerli, Iraq:
and from Pro-Russia fighters near the eastern Ukrainian city of Starobeshevo:
The Vexilla regis is a hymn written by Venantius Fortunatus to welcome the procession bringing a fragment of the True Cross to St Radegunda‘s convent in Poitiers: the first line translates to “The banners of the king go forth”.
Here it is, illustrated with battle flags flown by Catholic and Royalist troops during the War in the Vendée: