The origins of St Demetrios – even his actual existence – are more obscure even than those of his ‘companion’ St George, with whom he is frequently paired in art. Modern research supposes that he was probably a deacon martyred at Sirmium (circa 3rd century) and that he was later transformed by popular tradition into the great warrior saint, second only to St. George in popularity. His cult developed in Salonika, where he was known as 'The Great Martyr.' He is traditionally shown slaying the Bulgarian Tsar Kaloyan. After extended wars in the late 10th and 11th centuries, the Bulgarians were eventually defeated, the Byzantine Empire eventually controlling the entire Balkan peninsula.

Saint Demetrios is shown accoutered as an officer in the Roman (Byzantine) army. The painter accurately depicts the cloak, cuirass, tunic and leather skirt of a centurion of the 9th century[1].

The painter also takes interest in detailing the horse furnishings: saddle, shabrack, and the delightful checkerboard girth, all done with care and precision. All this, done with bold rich colours, presents an image of heraldic splendour. And yet the decorative effect veils the deeper meaning for the icon which wholly retains the other-worldliness of Byzantine monastic tradition. The saint’s visionary look inwardly concentrated, and the horse’s energetic charge denotes the movement inner energies. The ‘struggle’ surpasses the historical event warrior and king and becomes an allegory of mystical contemplation, the ‘spiritual warfare’ of the Hesychasts.

[1] https://www.britannica.com/topic/armour-protective-clothing