Saint Pope Sixtus II was the Bishop of Rome from August 31st, 257 until his martyrdom on August 6th, 258.
As Pope, Saint Sixtus restored relations between Rome and the African and Eastern churches - relations had been broken over the question of heretical baptism raised by Novatianism (a view that refused readmission to Communion of the Lapsi, or those who had denied their faith under the persecutions of Emperor Decius). Emperor Valerian began his nightmarish persecution of the Christian church in 258 with Saint Sixtus being one of the very first victims. Along side six other deacons - Januarius, Vincentius, Magnus, Stephanus, Felicissimus and Agapitus - Saint Sixtus was beheaded on August 6th. Just four days later the most well known Deacon of the time, Saint Lawrence of Rome, was martyred as well.
Pope Damasus I placed the following on Saint Sixtus's tomb in the catacombs:
At the time when the sword pierced the bowels of the Mother, I, buried here, taught as Pastor the Word of God; when suddenly the soldiers rushed in and dragged me from the chair. The faithful offered their necks to the sword, but as soon as the Pastor saw the ones who wished to rob him of the palm (of martyrdom) he was the first to offer himself and his own head, not tolerating that the (pagan) frenzy should harm the others. Christ, who gives recompense, made manifest the Pastor's merit, preserving unharmed the flock
His feast day was originally celebrated on the Transfiguration of the Lord , August 6th, but was moved during the 1969 revision to the date immediately following his death, August 7th.