Mars was the Roman god of war, and is one of the most commonly worshipped deities in ancient Rome. Because of the nature of Roman society, nearly every healthy patrician male had some connection to the military, so it is logical that Mars was highly revered throughout the Empire.
In early incarnations, Mars was a fertility god, and a protector of cattle. As time went on, his role as an earth god expanded to include death and the underworld, and finally battle and war. He is known as the father of twins Romulus and Remus, by the Vestal virgin Rhea Silvia. As the father of the men who later founded the city, Roman citizens often referred to themselves as "sons of Mars."
Before going into battle, Roman soldiers often gathered at the temple of Mars Ultor (the avenger) on the Forum Augustus. The military also had a special training center dedicated to Mars, called the Campus Martius, where soldiers drilled and studied.
The month of March is named in his honor, and several festivals each year were dedicated to Mars. Each year the Feriae Marti was held, beginning on the Kalends of March and continuing until the 24th. Dancing priests, called the Salii, performed elaborate rituals over and over again, and a sacred fast took place for the last nine days. The dance of the Salii was complex, and involved a lot of jumping, spinning and chanting. On March 25, the celebration of Mars ended and the fast was broken at the celebration of the Hilaria, in which all the priests partook in an elaborate feast.
During the Suovetaurilia, held every five years, bulls, pigs and sheep were sacrificed in Mars' honor. This was part of an elaborate fertility ritual, designed to bring prosperity to the harvest. Cato the Elder wrote that as the sacrifice was made, the following invocation was called out:
"Father Mars, I pray and beseech thee
that thou be gracious and merciful to me,
my house, and my household;
to which intent I have bidden this suovetaurilia
to be led around my land, my ground, my farm;
that thou keep away, ward off, and remove sickness, seen and unseen,
barrenness and destruction, ruin and unseasonable influence;
and that thou permit my harvests, my grain, my vineyards,
and my plantations to flourish and to come to good issue,
preserve in health my shepherds and my flocks, and
give good health and strength to me, my house, and my household.
To this intent, to the intent of purifying my farm,
my land, my ground, and of making an expiation, as I have said,
deign to accept the offering of these suckling victims;
Father Mars, to the same intent deign to accept
the offering of these suckling offering."
As a warrior god, Mars is typically depicted in full battle gear, including a helmet, spear and shield. He is represented by the wolf, and is sometimes accompanied by two spirits known as Timor and Fuga, who personify fear and flight, as his enemies flee before him on the battlefield.
In Greek legend, Mars is known as Ares, but was never as popular with the Greeks as he was with the Romans.