Sacramentum (oath) - Military Oath

Military Oath

The sacramentum militare (also as militum or militiae) was the oath taken by soldiers in pledging their loyalty to the consul in the Republican era or later to the emperor. The sacramentum as pertaining to both the law and the military indicates the religious basis for these institutions.

The sacramentum that renders the soldier sacer helps explain why he was subjected to harsher penalties, such as execution and corporal punishment, that were considered inappropriate for civilian citizens, at least under the Republic. In effect, he had put his life on deposit, a condition also of the fearsome sacramentum sworn by gladiators. In the rare case of punishment by decimation, the surviving legionaries were often required to renew their oath, affirming the role of state religio as the foundation of Roman military discipline.

By the 3rd century the sacramentum was administered annually, on 3 January, as attested by the calendar of state ritual discovered at Dura-Europos, the so-called Feriale Duranum, which dates to the reign of Severus Alexander (222-235 CE). In the later empire, the oath of loyalty created conflict for Christians serving in the military, and produced a number of soldier-martyrs. Tertullian condemned any Christian soldier's willingness to swear the sacramentum, since baptism was the only sacrament a Christian should observe.