Source Verification: Mars

Every claim below is either what a named ancient source attests, in its own line or section, or a point where the sources themselves disagree.

What the Sources Attest

Is Mars the same god as Ares?

Romans identified Mars with Ares and told similar stories about him as a war god, but their standing in their own religions is almost reversed: Ares is a relatively minor, often disliked figure in Greek myth, while Mars ranks second only to Jupiter in Roman state religion, with his own major priesthood and a direct role in the city's founding legend.

Source: Livy, Ab Urbe Condita 1.4

How is Mars the father of Rome's founders?

Livy records that Mars fathered Romulus and Remus by Rhea Silvia, a Vestal Virgin who had been forced into that role after her uncle Amulius usurped her father Numitor's throne and wanted no rival heirs. The twins were exposed by the river, survived by being suckled by a she-wolf, and eventually reclaimed their grandfather's throne before Romulus went on to found Rome - giving Mars a direct genealogical link to the city that Ares has to no Greek city.

Source: Livy, Ab Urbe Condita 1.4

What was the Campus Martius?

The Campus Martius, "Field of Mars," was a large open area in Rome set aside for military training, troop assemblies, and, for much of the Republic, the mustering point for the army before a campaign. It took its name and religious character directly from Mars, giving the god a specific, physical civic space in a way Ares had nowhere in Greek religion.

Source: Livy, Ab Urbe Condita 2.5

Who were the Salii, and what did they do for Mars?

The Salii were a twelve-member priesthood of patrician youths dedicated in part to Mars, who dressed in archaic armor and performed a ritual armed dance through the city each March, the month that takes its own name from the god and traditionally opened the Roman campaigning season. No equivalent priesthood existed for Ares in Greek religion.

Source: Cicero, De Natura Deorum 2.67

Why did Augustus build a temple to Mars Ultor?

"Mars Ultor," Mars the Avenger, commemorated the god's role in avenging the assassination of Julius Caesar; Augustus vowed the temple before the battle that punished the conspirators and completed it decades later as part of his own forum, tying Mars once again to a specific, contemporary Roman political event rather than only to abstract warfare.

Source: Ovid, Fasti

Where Accounts Differ

Mars's standing compared to Ares

Mars's stature relative to Ares is one of the clearest cases in Roman religion where interpretatio romana matched two gods by function while leaving their actual cultural standing completely different.

Sources

Primary sources

Livy, Ab Urbe Condita 1.4
Livy, Ab Urbe Condita 2.5
Cicero, De Natura Deorum 2.67
Ovid, Fasti