King Aśoka (reign: ca. 269-232 B.C) has been known as one of the most famous king through his significant contributions in the history of Buddhism. The first sign of his conversion to Buddhism has been said that after gaining the victory over the Kalinga Kingdom through a very disastrous war, Asoka suddenly realized by himself that he had made a huge mistake of killing hundred thousand of innocent people. Through this consideration, he had decided to abandon all of his aggressive behavior and converted himself to Buddhism. Under his leadership as a Buddhist king, he had contributed several kinds of contribution to the development of Buddhism; however, his contributions have been summed up into three important ways as following.
First of all, he applies the teachings of the Buddha into his rule through government and policies. After seeing the disaster of humanity in the Kalinga war which was caused by him in order to extend his empire, he realized that the victory through the war was not a real victory. Therefore, he stopped doing all such kind of violent acts anymore and started following Buddhist Dharma that probably was a primary step leading him to apply the basic principle of non-violence in Buddhism to govern the people in his empire. For instance, the rule of prohibition of the slaughter of animals, respect for all religious teachers, appointing the Dharma-mahāmātras or superintendent of Dharma etc. By applying the Dharma as the basic principal for his leadership, had changed him from someone who had been known by many people as Caṇḍāśoka (violent Aśoka) to Dharmāśoka (noblest Aśoka).
Second of all, he supports the community of Samgha to held the third Buddhist council and sends missionaries to spread Buddhism to different parts of the world. After the Buddha passed away, his disciples had faced several tough situations to unify the community of Samgha due to the disciplinary and doctrinal views. It had always been a hot debate over the discipline and doctrine in the community of Samgha for numbers of decades. Therefore, it is said that Aśoka had convened the third Buddhist council, prompted by his preceptor Moggaliputta Tissa, around 250 B.C. The results of the council are the new doctrine of Abhidharma, those holding heretical doctrines had been expelled from the orthodox community of Buddhist at Pataliputra, and seven groups of Buddhist missionary had been sent out from his capital to spread Buddhism to seven different places. Through the missionary efforts of Aśoka that Buddhism first becomes an international religion.
Third of all, he maintains Buddhism as a major religion in his kingdom. In the reign of king Aśoka, there was no religious discrimination against each other, all religious schools had been respected. In Rock Edict VII states that Aśoka wished members of all religions to live everywhere in his kingdom. However, Buddhism undeniably received more support from Aśoka than any other religious schools. Evidently, he built thousands of monasteries and stupas throughout his kingdom dedicating to Buddhism and ordered his ministers to install stone inscriptions and rock edicts describing the special events of the Buddha. Those stone inscriptions and rock edicts offer marvelous evidences for modern scholars who work in the field of Buddhist study.
In short, under his leadership, king Aśoka showed the world how important Buddhism was. He had used the basic principle of non-violence and compassion in Buddhism to organize the social welfare for his people. More importantly, through his missionary work, Buddhism had been spread throughout his empire as well as neighboring kingdoms.