Most history texts claim that Emperor Asoka’s conversion to Buddhism happened after the Kalinga war, which was fought in the ninth year of his reign. This claim is made on the basis of Asoka’s thirteenth rock edict which states that being disgusted by the bloodshed and destruction caused during the Kalinga war, Asoka converted to Buddhism. Since Asoka became the Emperor of the Maurya Empire in 273 BC, historians believe that he converted to Buddhism in 264 BC.
However, there are three Buddhist texts, the Asokavadana, the Asoka-sutra, and the Kunala-sutra, which suggest that Asoka could have become a Buddhist, or become inspired by Buddhism, while he was the crown-prince and his father Bindusara was the Emperor. These texts are hard to date, as amendments have been made to them for centuries. In their book, Pilgrimage: Past and Present in the World Religions, historians John Elsner and Simon Coleman have posited that the earliest version of the Asokavadana was composed immediately after Asoka’s death.
According to these Buddhist texts, during Bindusara’s reign there was a rebellion in Gandhara, a province located in modern-day Pakistan. To quell the rebellion, Bindusara dispatched an army led by crown-prince Asoka. The Ashokavadana states that when Asoka arrived in the province, the people of Gandhara welcomed him. They told him that the rebellion was against the evil ministers, not the king. After that Asoka governed Gandhara for several years as his father’s viceroy. In that period, Gandhara was a major center of Buddhist learning.
During Asoka’s viceroyalty, Buddhism gained further strength in the entire North-West region. In his 1935 translation of Kalhana’s Rajatarangini (The Saga of the Kings of Kashmir), R. S. Pandit (Nehru’s brother-in-law) writes: “It was during Asoka’s efficient viceroyalty of the North-West that Buddhism gained strength in these parts and spread to Kashmir and Afghanistan. He covered these countries with Sangharamas and monuments, some of which still survive such as his inscriptions at Shahbazgarhi and his celebrated tower near Kabul known as the Minar Charki.”
Asoka probably converted to Buddhism while he was serving as the viceroy of Gandhara, otherwise he would not have spent the resources of the Maurya Empire on constructing Buddhist monuments in the North-West domain of his viceroyalty.