Warrior saints. Located in the right part of the arch, above the icon of the ‘Crucifixion’.
Byzantine fresco from the 12th century.
Warrior saints of the Early Christian Church are prominent in the history of Christianity. The persecution of Christians under Diocletian or other Roman Emperors usually furnished the background for soldier-saint hagiography which has a common theme: a soldier of the Empire who has become a Christian finds that his devotion conflicts with traditional religious practices of the Roman military. Refusing to participate in rituals of loyalty to the Emperor, he is subjected to corporal punishment that escalates to torture—which miraculously may not affect him—but he does not deny his faith and is martyred. Amongst them: St. Demetrius, St. George, St. Sebastian, St. Theodore, St. Sergius and Bacchus.
Correspondent: J.M.Criel, Antwerpen.
Sources: Website of ‘stnicholascenter.org’ & Wikipedia.
Another knowledgeable viewer informed me: "Here is represented Saint Longinus, the Centurion who was present at the death of Christ and, according to the legend, is sometimes identified with the man who pierced the body of Our Lord. Interestingly, the Centurion is represented dressed in the East-Roman armour of the 11th - 12th century, i.e. a golden iron Klibanion (lamellar armour), a round infantry shield (Skoutarion) and a helmet (Kassis). "