This panel was probably part of an altarpiece dedicated to the Holy Cross, a relic that was much venerated in the Middle Ages. Through repeated retelling, its story took on some of the qualities of a chivalric romance. That story included the adventures of the Byzantine emperor Heraclius, who rescued the True Cross and returned it to Jerusalem after its capture by Chosroës, king of Persia.

Here Heraclius defeats a king who is probably meant to be the son of Chosroës. The emperor can be identified by the closed imperial crown that caps his helmet, the double-headed eagle symbol on the trumpet and the trappings of his followers’ horses, and the fact that he is about to behead his opponent. This exciting narrative provides an excuse for a vivid display of armor and weaponry.