They were the 14,000 infants massacred in Bethlehem at the order of King Herod of Bethlehem in the hope of eliminating the infant Jesus, afraid that he would bring an end to his kingdom. They died for Christ at the age of innocence, and are therefore glorified by the Church as the first holy martyrs in its history. Although none of these infants had been baptized in water, they were all baptized, in the eyes of the Church, in the blood of their martyrdom.
For King Herod, the murder of the infants of Bethlehem was a part of his ‘plan B’ for killing infant Jesus. His initial plan was to find out his whereabouts with the aid of the Magi. The Magi noticed the rise of a new star on the horizon, recognized it as the sign of the coming of the Messiah, and followed it to offer their gifts. Having shared their plans with Herod, they promised to return to him and report on their visit. However, an angel in a dream warned them not to do it and return to their country by a different route.
King Herod was hopeful that the infant Jesus would be among the 14,000 infants he had ordered killed. Yet, Simeon the God-receiver went before the people of the Jerusalem temple and announced the birth of Christ. He knew the wrath of King Herod and died of his sword. The Holy Prophet and Priest Zechariah also met a martyr's death at the hand of King Herod's assassins because he did not disclose the whereabouts of his son John, the would-be Baptist of Christ.
King Herod's schemes ultimately failed, and he died a slow and horrible death from being eaten by worms. He destroyed his kingdom with his own hands, by murdering his wife, his three sons, his brother and sister, and her sons. He also killed seventy wise men members of the Jewish Assembly (the Synedrion), several chief priests and secretaries. He did not want anyone to rejoice at his leaving.
The relics of the Holy Infants were put to rest in the Church of Saint James in Constantinople. A portion of the relics is found in Pantokrator Monastery on Mount Athos.