Aedes Martis (Nova Roma)
Mars, god of war, was originally an agricultural god whose character changed with that of His people. For this reason, He is the most Roman of the gods, representing the abundance of the fields, and the battles that must be won to keep and enlarge the provinces that kept Rome fed and thriving. He is the son of Iuno and Iuppiter, husband of Bellona, and the lover of Venus. He was the most prominent of the military gods that were worshipped by the Roman legions. The martial Romans considered Him second in importance only to Iuppiter. His festivals were held in March (named for him) and October.
As the word Mars has no Indo-European derivation, it is most likely the Latinised form of the agricultural Etruscan god Maris. Initially Mars was a Roman god of fertility and vegetation and a protector of cattle, fields and boundaries and farmers. In the second century BC, the conservative Cato the Elder advised "For your cattle, for them to be healthy, make this sacrifice to Mars Silvanus you must make this sacrifice each year" (De Agri Cultura 83). Mars later became associated with battle as the growing Roman Empire began to expand, and he came to be identified with the Greek god Ares. Unlike his Greek counterpart, Mars was generally revered and rivaled Iuppiter as the most honoured god. He was also the tutelary god of the city of Rome. As He was regarded as the legendary father of Rome's founder, Romulus, it was believed that all Romans were descendants of Mars.
Temple of Mars UltorFull article at Wikipedia.
Augustus created the cult of "Mars the Avenger" to mark two occasions: his defeat of the assassins of Caesar at Philippi in 42 BC, and the negotiated return of the Roman battle standard sthat had been lost to the Parthians at the Battle of Carrhae in 53 BC. The god is depicted wearing a cuirass and helmet and standing in a "martial pose," leaning on a lance he holds in his right hand. He holds a shield in his left hand. The goddess Ultio, a divine personification of vengeance, had an altar and golden statue in his temple.
The Temple of Mars Ultor, dedicated in 2 BC in the center of the Forum of Augustus, gave the god a new place of honor. Some rituals previously conducted within the cult of Capitoline Jupiter were transferred to the new temple, which became the point of departure for magistrates as they left for military campaigns abroad. Augustus required the Senate to meet at the temple when deliberating questions of war and peace. The temple also became the site at which sacrifice was made to conclude the rite of passage of young men assuming the toga virilis ("man's toga") around age 14.
On various Imperial holidays, Mars Ultor was the first god to receive a sacrifice, followed by the Genius of the emperor. An inscription from the 2nd century records a vow to offer Mars Ultor a bull with gilded horns.