Pope Sixtus II was the twenty-fifth pope, counting from Saint Peter. He may have been Greek, but that is all we know of his youth.
Sixtus was deacon under Pope Stephen. This was a difficult time. Those who had escaped death during the Decian persecutions had not always done so through luck. Some had bought certificates stating that they had done the required sacrifices to the gods. Some had denied being Christian. And some actually did sacrifice to the gods. Luckily, by 251, the persecutions had ended with the death of Decius. Gallus succeeded him but only reigned eighteen months before being assassinated. Aemilius ruled for four months but was never even acknowledged by the senate before he was killed.
Valerian, censor and chief of the senate, coming from a well known family, was acknowledged by the senate quickly. A superstitious man, Valerian was accepting of the different religions in his empire for the first three years. He even had many religious people in the palace, influencing peace.
During that period, those Christians who were lapsed from the Church wanted to return. One sect had developed that taught that the "lapsi" could not return and must wait until the Final Judgement, an argument which was not considered orthodox. Meanwhile, this sect, and others, were baptizing others into the Church. Some of the bishops, especially in Africa and the East, were of the opinion that those who had been baptized by the sects could not be truly Catholic until re-baptized. Pope Stephen argued that point against the bishops, including St. Cyprian, and held his ground against their opinions. This forced a very unhappy split between Rome and the outlying areas by the time Stephen died.
Sixtus, partly due to the advice of St. Dionysius, bishop of Alexandria, chose a more conciliatory path. He indicated that his way (no re-baptism) would be the way of Rome and invited others to adhere to it. But there was no punishment if they did not follow him.
Meanwhile, Valerian had raised Macrianus to the level of what would be a prime minister. Macrianus was a man addicted to black art and the Persian sect of Magians. St. Dionysius referred to him as the archmagian of Egypt. Utilizing his knowledge of Valerian's superstitious nature, he convinced the emperor that the Christians were arch enemies of black art. Valerian quickly established a law that Christians must participate in the national cult of pagan gods. They were forbidden to gather in cemeteries (catacombs) and punishment would be banishment or death.
Somehow, Sixtus kept his people together and they held Masses where they could. However, less than a year after he was consecrated, Valerian, on his way to fight the Persians, changed his rule, sending letters back demanding the death of bishops, priests and deacons.
Trying to keep his people safe, on August 6, Sixtus met for Mass with his flock in the little known Catacombs of Praetextatus, on the Appian Way. During Mass, soldiers came in. Sixtus and his deacons, Januarius, Vincentus, Magnus, Stephanus, Felicissimus and Agapitus, were taken. It is not sure if they were immediately killed or if they were taken for a mock trial and then brought back to die. St. Lawrence, the familiar archdeacon died three days later.
God did not look kindly on Valerian. The emperor was taken prisoner by the Persians and lived the last seven years of his life as a slave. the Christians continued to pray for the people who persecuted them.