When we speak of the Oath of the Horatii we can be referring to one of three things, all of which are driven by the ancient tale of the Horatii and Curiatii:
The tale of the Horatii and Curiatii is one of the myths which even in Roman times lay at the foundations of “Romanity”, it is written by the ancient Roman writer Livy “ab urbe condita”. Like other tales of its kind it was about personal sacrifice and valour which in the extreme saved the day for the future empire. It refers to a period around 650BC when Rome was ruled by its 3rd King Tullus Hostilius when it was still a budding village set on hilltops vying for local domination against the nearby city of Alba Longa.
It was agreed that the war would be settled through a fight to the death between triplet brothers from either camp – the Horatii (Romans) and Curiatii (Alba Longans). Two of the Horatii brothers died but all three of the Curiatii were wounded. The last of the Horatii had the best of the three wounded and so Rome won the day and the war. Alba Longa was subdued and destroyed, its citizens transferred to Rome.
However the event carried a twist in the tale which also tells of Law and Justice in ancient Rome: The Horatii brothers had a sister, Camilla, who happened to be in love with one of the Curiatii. When she learned of her lover’s death she wept and was duly killed by her surviving brother for having wept the enemy. This was clearly murder and so the hero was due to be put to death had it not been for their father who appealed to the people’s assembly and gained a pardon for his son in return for sacrifices to atone the misdeed.
According to tradition, the father erected the Tigillum Sororium (an arch as a symbolic yoke) which the eldest son of the family walked under every year henceforth. The same rudimentary wooden arch became part of regular military processions at the end of the war season (1st October) and was possibly the archetypal triumphal arch so unique to Roman architecture and later built into the structure of the earliest Christian-Roman basilicas.