All that we know for certain about St. Demetrius is that he was martyred during the persecution of Diocletian (3rd/4th century) at Sirmium in Dalmatia. Afterward a perfect of Illyria named Leontius introduced his cult to Salonika, transferred some of his relic there, and built a temple in his honor in both cities. From the 5th century on, Salonika was the great center of the cult of St. Demetrius, and his imposing church was destroyed only in 1917.
According to a legendary history, St. Demetrius was a citizen of Salonika who was arrested for proclaiming the Faith. He was then slain without a trial as he was being detained in a room of the public baths. Other accounts make him a proconsul and a warrior-Saint, and this latter capacity he almost equaled the popularity of the great legendary figure St. George. Both of these Saints were adopted as patrons by the crusaders and a story says that they were seen in their ranks at the Battle of Antioch in 1098.
St. Demetrius is still very popular in the East, and his feast is celebrated with solemnity in the Eastern Liturgy.
PRAYER: Almighty and ever-living God, you enabled St. Demetrius to fight for justice even unto death. Through his help, grant that we may tolerate all adversity and hasten with all our might to You Who alone are life. Amen.