Ashoka was the son of Bindusara, who ruled the Mauryan empire from 269 to 232 B.C. Ashoka reigned over most of the Indian subcontinent, from present day Afghanistan to Bengal and as far south as Mysore.
While the early part of Ashoka's reign was apparently quite bloodthirsty, he became a committed Buddhist after his conquest of Kalinga, on the east coast of India in the present day state of Orissa. The brutality of this conquest led him to adopt Buddhism and he used his position to further the relatively new religion. The remaining portion of his reign had an official policy of nonviolence, ahimsa.
The source of much of our knowledge of Ashoka is the many inscriptions he had carved on pillars and rocks throughout the empire. These inscriptions promoted Buddhist morality and encouraged nonviolence and adherance to dharma (duty or proper behavior).
Following Ashoka's enlightened reign, the Mauryan empire soon declined and fragmented. Such a large portion of the subcontinent would not be united again until British rule some 2,000 years later.