Marcus Atilius Regulus (3rd century BC) Roman consul
Marcus Atilius Regulus was consul in Rome from 267 to 256 BC. In 256 he enjoyed some victories against the Carthaginian army in Africa. During the peace talks, he insisted on them giving up their independence. In the renewed battle, Regulus' army was completely destroyed.
Regulus was captured, but the Carthaginians offered him a deal. He could return to Rome in exchange of Carthage prisoners, provided he would come back to Carthage in case his mission would fail. According to Roman historian Titus Livius there were also peace conditions included in the deal.
But in the Senate Regulus himself argued that the exchange was not in Rome's interest (as he was old and the Carthaginian prisoners were young) and he asked the Senate's permission to return to Carthage as his oath demanded. Many would just have backed out of the deal, but not Marcus Atilius Regulus. He refused to break the word that he had pledged to the enemy and returned to Carthage where he died a cruel death in captivity. According to Marcus Tullius Cicero, the greatest of Roman orators, "he was not ignorant of the fact that he was going to a most cruel enemy and to exquisite torture; still, he thought his oath must be kept." The story might be apocryphal but made Regulus an exemplum of Roman virtue (and reinforced the reputation of Carthage for cruelty).