Saint Fabian was martyred by the brutal persecution unleased by Emperor Decius in 250AD. The relentless and brutal Christian persecution meant that it was impossible to choose a successor to Saint Fabian. Hence, Saint Peter's throne had to remain vacant for more than a year after the demise of the former Pope.

However, the cruel Emperor Decius had to stay away from Rome on a military campaign. Seizing this opportunity and seeing his absence as a divine intervention, the church leadership immediately began the process for electing a new pope. Sixteen bishops gathered in Rome and in A.D251, Saint Cornelius was chosen as the twenty-first Pontiff of the Catholic Church. Pope Cornelius began his Pontificate in March 251AD.

Thought to have been born to Italian Parents in Rome, the election of Pope Cornelius was not a pleasing one to all. After the martyrdom of Pope Fabian, Novatian, who had led the Roman Church for a year and had intended to be elected as the successor, completely disapproved of the current Papal election. Novatian’s followers, who propagated the Novatian theology, anointed him as an anti-pope leading to conflicts and tensions within the church. 

During the persecution of Decius many people apostatized from faith and worshiped idols unable to bear persecution. Once they repented of such wrongdoings and expressed their desire to return to the Church, the question then arose whether baptise them again before allowing them back to Church.

Pope Cornelius consulted Saint Cyprian of Carthage and heeding his advice allowed such faithful to re-enter the Church without the necessity of a re-baptism. Novatian and his followers opposed their readmission to the Church and demanded that such apostates should not be readmitted to the Church in any way.

They quoted the Old Testament where it is stated that idolatry is a sin that could never be forgiven, and therefore taught that the power to forgive such sins was not in the Church’s authority rather only God's after their death. This attitude of Novatian and his followers led to a great schism in the Church.

Pope Cornelius convened a synod in Rome to overcome the sectarianism that arose and resolve such issues. The synod reestablished that Pope Cornelius was the true successor of Saint Peter, and excommunicated the schismatic Novatian and his followers.

The Synod also decided that sinners could be readmitted to the Church through repentance and appropriate acts of penance. Likewise, the theological truth that there is no unforgivable sin was established through the synod.

In the beginning of AD252, Emperor Gallus, the successor of Emperor Decius, unleashed fresh persecutions against the Church. During this time of religious persecution, under the leadership of Pope Cornelius, the faithful courageously bore witness to their faith.

Enraged, Emperor Gallus exiled Pope Cornelius to Centumcellae, a place outside of Rome.

Pope Cornelius was called to eternal rest in June AD253, having endured hardships of living in exile and advanced age. The Church celebrates his feast day on September 16.
-edit&transl. SM