Duel of Champions is a 1961 Italian production (the Italian title is: Orazi e Curiazi ). The movie is about the Roman legend of the Horatii. The Horatii were triplet brothers from Rome who fought a duel against triplet brothers from Alba Longa, the Curiatii. It was agreed that the settlement of the war would depend on the outcome of the duel.
The legend of the Horatii has been told by Roman historian Livy. As with a lot of the history of Rome during the Kingdom, it is not sure whether this event (the duel) happened or not. What is certain though is that king Tullus Hostilius (672-642 B.C.) did go to war with Alba Longua and that the war ended with Rome's victory.
To go back to the story / legend of the Horatii, the Horatii male triplets were the same age as the Curiatii male triplets from Alba Longa. In the duel, the three of the Curiatii were wounded but the two of the Horatii were killed. The only Horatii remaining was Publius. Publius turned as if to escape and the Curiatii chased him. But the Curiatii became separated because of their wounds. This enabled Publius to kill them one by one.
When Publius returned to Rome to celebrate his victory, his sister could not conceal her grief and cried as she knew that the Curiatii triplets were all killed including the one she was engaged to. Publius then killed his sister and declared: "so perish any Roman woman who mourns the enemy." Publius was condemned to death for killing his sister but was later saved by an appeal to the populace made by his father. We note that appealing to the populace (or more specifically to the assembly of the people) was a legal practice in Rome that gave every condemned Roman a last chance.
Publius' father was required to offer sacrifices which were continued by the gens Horatia, and Publius was required to pass under a beam laid across the street. The beam (Sororium Tigillum or "sister's gibbet") remained in the city thereafter. It is also interesting to note that the spoils of the Curiatii (cloth from the Curiatii triplets) were hung at a place known as the Pila Horatia.
There is a beautiful painting by Jacques-Louis David about the legend of the Horatii called the Oath of the Horatii (1784).