Plutarch, Romulus
Bernadotte Perrin, Ed.

16. Now the Sabines were a numerous and warlike people, and dwelt in unwalled villages, thinking that it behoved them, since they were Lacedaemonians colonists, to be bold and fearless. [2] Nevertheless, seeing themselves bound by precious hostages, and fearing for their daughters, they sent ambassadors with reasonable and moderate demands, namely, that Romulus should give back to them their maidens, disavow his deed of violence, and then, by persuasion and legal enactment, establish a friendly relationship between the two peoples. But Romulus would not surrender the maidens, and demanded that the Sabines should allow community of marriage with the Romans, whereupon they all held long deliberations and made extensive preparations for war. [3] But there was one exception. Acron, king of the Caeninenses, a man of courageous spirit and skilled in war, had been suspicious of the daring deeds of Romulus from the beginning, and now that this violence had been done the women, thinking him a menace to all peoples, and intolerable unless chastised, at once rose up in arms, and with a great force advanced against him.¹ [4] Romulus also marched out to meet him. But when they were face to face and had surveyed each other, they challenged mutually to single combat before battle, while their armies remained quiet under arms. Romulus, then, after making a vow that if he should conquer and overthrow his adversary, he would carry home the man's armour and dedicate it in person to Jupiter, not only conquered and overthrew him, but also routed his army in the battle which followed, and took his city as well. To the captured citizens, however, he did no harm beyond ordering them to tear down their dwellings and accompany him to Rome, where, he promised them, they should be citizens on equal terms with the rest.

[5] Now this, more than anything else, was what gave increase to Rome: she always united and incorporated with herself those whom she conquered. But Romulus, after considering how he might perform his vow in a manner most acceptable to Jupiter and accompany the performance with a spectacle most pleasing to the citizens, cut down a monstrous oak that grew in the camp, hewed it into the shape of a trophy, and fitted and fastened to it the armour of Acron, each piece in its due order. [6] Then he himself, girding his raiment about him and wreathing his flowing locks with laurel, set the trophy on his right shoulder, where it was held erect, and began a triumphal march, leading off in a paean of victory which his army sang as it followed under arms, and being received by the citizens with joyful amazement. This procession was the origin and model of all subsequent triumphs, and the trophy was styled a dedication to Jupiter Feretrius, so named from the Roman word ‘ferire,’ to smite; for Romulus vowed to smite his foe and overthrow him. [7] And such spoils were called ‘opima,’ because as Varro says, ‘opes’ is the Roman word for richness; but it would be more plausible to say that they were so called from the deed of valour involved, since ‘opus’ is the Roman word for deed or exploit. And only to a general who with his own hand has performed the exploit of slaying an opposing general, has the privilege of dedicating the ‘spolia opima’ been granted.

Furthermore, only three Roman leaders have attained this honour: Romulus first, for slaying Acron the Caeninensian; next, Cornelius Cossus, for killing Tolumnius the Tuscan² and lastly, Claudius Marcellus, for overpowering Britomartus, king of the Gauls.³ [8] Cossus indeed, and Marcellus, already used a four-horse chariot for their entrance into the city, carrying the trophies themselves, but Dionysius⁴ is incorrect in saying that Romulus used a chariot. For it is matter of history that Tarquin, the son of Demaratus, was first of the kings to lift triumphs up to such pomp and ceremony, although others say that Publicola was first to celebrate a triumph riding on a chariot.⁵ And the statues of Romulus bearing the trophies are, as may be seen in Rome, all on foot.