In the 3rd century BC the great Mauryan emperor, Ashoka saddened by the bloodshed of war, became a Buddhist. The conversion of Ashoka the Great, was an important turning point in the history of Buddhism. He declared that hence-forth he would make the Buddha-Dhamma the basis of all his actions in the spiritual as well as temporal fields. Ashoka convened the third Buddhist council at Pataliputra (modern Patna) and he launched a vigorous campaign to preach and propagate the message of the Buddha. With his systematic and energetic efforts, Ashoka took out the gospel of the Buddha from caves and monasteries and made it a national religion.
The efforts of Ashoka to popularise the gospel of the Buddha created a stir amongst the Buddhist masses. The stupas and railings which we see today at Sanchi and Bharhut are the creation of the pious devotees of the Buddha who came about 50-100 years after Ashoka. The religion of the Buddha had, by the 2nd century BC become a force to reckon with. Its popularity further increased when the Greeks and the Kushans, embraced Buddhism.
The period (200BC-700AD) saw the emergence of a number of illustrious saint-scholars who made an immense contribution to the Buddhist philosophy and religion.
Ashvaghosha, a poet, dramatist, musician, scholar and debater went on foot from village to village, town to town and city to city playing on his instruments and singing songs in praise of the Buddha. Thus he took Buddhism to every hearth and home.
Nagarujana, who was a friend and contemporary of the Satavahana king-propounded the Madhyamika school of Buddhist philosophy, popularly known as Sunyavada.
Asanga and Vasubandhu, who were brothers, flourished in Punjab in the 4th century A.D. Asanga was the most important teacher of the Yogacara or Vijnanvada school founded by his guru, Maitreyanatha. Vasubandhu's greatest work, the 'Abhidharmahosa' is still considered an important encyclopedia of Buddhism.
Buddhaghosha, who lived in the 5th century A.D was a great Pali Scholars. The commentaries and the Visuddhimaga written by him are key to the 'Tripitaka' theory of Buddhism. (More details on Tripitaka in Sacred Scriptures)
Dinnaga, the last mighty intellectual of the 5th century, is well known as the founder of the Buddhist logic. He is often referred to as the father of the Medieval Nayaya as a whole.
Buddhapalita and Bhavaviveka were important exponents, in the 5th century, of the Sunyavada doctrine propounded by Nagarjuna.
The grand tradition of Vasubandhu, was continued by Chandrkirti, Sthrimati and the younger Dhammapala.
The Sunyavada doctrine was further interpreted by the distinguished thinkers like Aryadeva, Santideva, Santaraksita and Kamalasila.
Dharmakirti, who lived in the 7th century AD, was another great Buddhist logician. Dharmakirti was a subtle philosophical thinker and dialectician. His writings mark the highest summit reached in epistemological speculation by later Buddhism.
Harsha (606-647AD) was the last illustrious Buddhist ruler. He had to assume power of the Thanesar and the Kanauj dynasties under dramatic circumstances. During his period, there were about 10,000 monasteries and about 75,000 monks in India. After the death of Harsha in 647 AD, Buddhism began declining rapidly. By the 12th century AD, Buddhism in India was only confined to a small pocket in north-east India. When Muslim army advanced towards Bihar, sacked the Buddhist establishments, massacred most of the monks, the route of Buddhism was complete.
Simultaneously, with its spread in India, Buddhism also crossed the borders of India and gained firm ground. Beginning with the missionary activities launched by Ashoka in the third century BC, when he send his own son and daughters to Sri Lanka, on a Buddhist Mission, it gradually spread across much of Asia. Though Buddhism declined in India due to various reasons, it is still a living religion in almost all parts of south-east Asia.