The Crucifixion by Diego Velazquez, 1632AD
You might read, further: Fisheaters: Roodmas (This entry focuses on the Finding of the Cross, "Roodmas," by St. Helen, which was originally celebrated on 3 May, but has since been combined with the September celebration)
Old Catholic Encyclopedia: True Cross (This notes the origins of both Finding and Exaltation, which are now celebrated on the same day.)
Old Catholic Encyclopedia: Mount Calvary
The Communion Antiphon for this feast is splendid, indeed: Per signum Crucis de inimicis nostris libera nos, Deus noster. By the sign of the Cross, deliver us from our enemies, O Thou our God.
Most folks are not familiar with the historical origin of this September feast day, and the circumstances that gave rise to this particular observance. Let us turn our thoughts back to the 7th century, in the Byzantine (Eastern Roman) Empire, where the Emperor is Heraclius I.
Heraclius I (610-641) was son of the governor of Africa – and he was a Catholic. Persia, the Sassanid Empire, would be his first concern. There had been a long standing feud between these two Empires – indeed, Emperor Valerian had been stuffed with straw after being captured by them in the 200sAD.
The war with Chosroes II was not going well at all for the Byzantines, as Heraclius was still trying to gain full control of the Empire. The Persian offensive launched in 611 overran Syria, Antioch, the Holy Land, and much of Asia Minor. A counterattack in 613 was fruitless. On Easter, in 614, Jerusalem was besieged, and would be sacked by the Persians. It fell after a thirty day siege and a three day rampage, and major portions of the True Cross were lost to these pagans, who gave the city to the Jews. Persian Christians, it would seem, did ensure that the relic was preserved. In 616 Alexandria and Egypt fell to the Persians – 80,000 thought killed in the city.
A fresco of a battle between Heraclius and the Sassinid Persian forces by Piero della Francesca (+1492AD).
At this point, Heraclius contemplated falling back to Africa, and abandon Constantinople itself. The Patriarch Sergius, however, offered the treasures of the Church to the Emperor to fund a defense. In 622 Heraclius and his trained army was ready to march – to get the venture off on the right foot they attended a huge liturgy at the Cathedral, and marched with image of Our Lord. This was it – the final hope of the Christian Empire. Heraclius marched into the mountains above Armenia in the winter of 623 – and won three battles! The next year (624), with his force of 120,000 he invaded Armenia itself, avoiding Persian traps. In 625, he smashed several Persian armies, and turned to Persia itself. In 626 a Slav-Avar army under Persian command besieged Constantinople. Heraclius had sent a relief force under his brother that saved the city – it had held out long enough with the encouragement of the Patriarch. This forced then rejoined Heraclius for the final march into Persia in 627 – plus Mongol allies. The commander of the Persian army fought Heraclius in one-on-one combat, and the Emperor killed him! Victory! Chrosroes II was killed the next year, in 628!
Heraclius returning the Cross to Jerusalem by Miguel Bernat, image from 1480AD.
The Persian agreed to withdraw from the Empire and return the cross – and in 630AD Emperor Heraclius carried the relics of the True Cross into Jerusalem himself – the origin of our Feast of the Triumph of the cross.
Recommended Source: Byzantium at War by Haldon