Ashoka (268-232 BCE) was the son of Bindusara and the grandson of Chandragupta Maurya (the founder of the Mauryan Dynasty). During the peak of his reign, Ashoka ruled almost all parts of the current-day Indian subcontinent except for some parts of Southern India.
He was known to be a cruel and ruthless conqueror during his initial years as an emperor. But after defeating the state of Kalinga (modern-day Orissa) in a fierce battle, Ashoka realized the futility of armed conquest. The bloodshed and the destruction of that battle made him renounce war and he started following the principles of Buddhism. This led to the significant promotion of Buddhist ways of life across the continent.
He went on to construct thousands of stupas and viharas (monasteries) and sent Buddhist missionaries to several different parts of the world (modern-day Thailand, China, Sri Lanka, and Greece).