The Crisis of the Centurion's Oath
The defining episode of Marinus's life is the dispute over his promotion. He had served capably and was about to receive the rank of centurion when a competitor for the same post raised an objection: under ancient law, the holder of such Roman office was required to offer sacrifice to the emperor, and Marinus, as a Christian who would not sacrifice, was therefore ineligible.
Until this moment Marinus had kept his Christian faith secret. The challenge forced the question into the open, and he professed his faith plainly, explaining that it prevented him from making the demanded sacrifice. The matter thus turned on the conflict between Roman civic-religious duty and Christian confession that lay at the heart of the pre-Nicene persecutions.
The Choice Between Sword and Gospel
After Marinus confessed his faith, the presiding judge gave him three hours to change his mind. During that interval the bishop Theotecnus intervened, leading Marinus into the church and to the sanctuary.
There the bishop pointed to the sword that hung at Marinus's side and at the same time placed before him the book of the divine Gospels, telling him to choose which he preferred. Without hesitation Marinus stretched out his right hand and took the Scripture. The bishop blessed him to hold fast to God. Returning to the tribunal more resolute than before, Marinus refused the ritual sacrifice and was led away to be beheaded.
Sources and Burial
The earliest surviving account of the martyrdom is given by Eusebius of Caesarea in his Ecclesiastical History, who sets the events in the reign of the emperor Gallienus. Eusebius records that the centurion's rank was marked by the vine-branch insignia, names the judge as Achaeus, and identifies the bishop as Theotecnus.
Eusebius further relates that Astyrius, a Roman senator of wealth and distinction, was present at the execution, took up the martyr's body, and gave it a costly and fitting burial; this senator is himself venerated as a martyr. The in-repo record places the saint's origin in Italy / Rome and observes his feast on December 16, while the historical accounts associate the soldier-martyr of this name with Caesarea in Palestine.