Pope Eusebius reigned for four months during the year 309 or 310. He should not be confused with other Saints Eusebius nor with Eusebius of Caesaria who wrote the great book Ecclesiastical History, shortly after this pope died.
Eusebius was Greek and either his father or he was a physician. At some point he came to Rome and became involved with the Roman Church's government. He became Bishop of Rome after the previous pope, Marcellus I, was banished by Emperor Maxentius.
As you readers will remember, Emperor Diocletian dictated a persecution of Christians in 303-305. Those who would not sacrifice to the Roman gods were killed, fined, jailed or all of the above. This lead many Christians to lie about their faith, run away or convert to the state religion. Eventually, the persecutions subsided and the emperors turned to more important items, like the Goths invading the Black Sea area.
Once it was safe to come out of the woodwork, so to speak, many former Christians, known as lapsi (lapsed), wanted to come back into the fold. There were three main sets of thoughts on this subject. Those following Novatian, the popular preacher, thought that a mortal sin, ie, lapsing, murder and adultery, could not be forgiven by anyone but God, Himself, at the last Judgement. Thus, the lapsi, according to this way of looking at it, could never, in this life, join in the Mass or the sacraments. The opposite take was that preached by Heraclius. His teaching was that the Church should accept back the apostates with little or no consequences. The teaching of Pope Marcellus and other orthodox presbyters was that all lapsi should be welcomed back after rather severe penances had been undergone. This teaching was prominent despite the rumor that one of the previous popes had, himself, been an apostate, a rumor which has never been proven.
Eusebius had to have known what he was getting himself into, since his predecessor had been exiled for not containing these two other groups. But he took on the responsibility, anyhow. Unfortunately, the apostates under Heraclius refused to take no for an answer. They demanded immediate access to the sacraments. When they were not granted this, they rioted in the streets of Rome. Chances are that, like most riots, they didn't remain in their little ghetto, but spilled out into the main streets of the city. Apparently, Heraclius thought he could compel the bishop to conform to his theories.
Emperor Maxentius was not going to put up with rioting in his capital city. Within months, his soldiers had captured both Bishop Eusebius and Heraclius and banished them to Sicily. Eusebius died very shortly thereafter and was briefly buried there.
When Eusebius' successor, Miltiades, was elected a year later, 311, he ordered the past pope's body to be brought to Rome where he was buried in the catacomb of Callixtus. Later in the century, Pope Damasus wrote, on a marker at the burial site, an epitaph of eight lines, in classic poetic form. It noted the banishment Eusebius went through and how he upheld the defense of ecclesiastical discipline, which is why he deserved the title of martyr and saint.