Ares is the son of Zeus, monarch of the Olympian Gods, and his wife Hera. Ares was worshiped as the god of war in both ancient Greece and ancient Rome. After the rise of Christianity in the Roman Empire, Zeus allowed the worship of the Olympians to die out, and Ares was no longer allowed to act as patron god of warriors. As a result over the ensuing centuries Ares grew increasingly dissatisfied with Zeus' rule. He has tried to conquer Olympus on several occasions sometimes in league with his uncle Pluto, god of the Olympian underworld. His half-brother Hercules has opposed his attempts at conquest almost every time sometimes with the help of his allies including Thor the Asgardian god of thunder, and the Avengers. Ares has hated Hercules since Hercules killed Ares' monstrous Stymphalian birds during Hercules' original twelve labors.
Ares has fought the Avengers on numerous occasions, as well as his half-brother Hercules. Ares has also fought the Champions, the Eternal Ikaris and a variety of other denizens of Earth. Recently warriors from the East have attacked Olympus and the Olympians have sought the assistance of Ares. Ares who had retired from warfare and the life of the gods has only recently joined the battle due to the kidnapping of his son.
Wanting his son to live the life of a mortal instead of under the rule of his father, Ares decided to raise his son on Earth instead of Olympus. While at work Ares was confronted by Ms. Marvel and Iron Man to register under the Civil War|Superhuman Registration Act and offered a job as an Avenger. Ares agreed as long as they would match his hourly pay.