Starting point: the middle Ganges plain
Buddhism began in the northeast of the Indian subcontinent, in the region of the middle Ganges plain, in the lifetime of the teacher known as the Buddha. Scholars differ on his dates; many place his life roughly in the 5th century BCE, while some older traditional reckonings put it earlier. The places most closely tied to his life are Lumbini, Bodh Gaya, Sarnath and Kushinagar, and the early community moved between towns of the old kingdoms of Magadha and Kosala, including Rajgir.
The movement began as a community of wandering monks and nuns with lay supporters. For its first few centuries it was one of several teaching traditions in India, and the evidence for exactly how it grew is thin. Much of what we know comes from texts written down later, from inscriptions and from archaeology.
Patronage and the first movement outward
A turning point in many accounts is the reign of the Mauryan emperor Ashoka in the 3rd century BCE. Inscriptions and later Buddhist chronicles associate him with support for the Buddhist community, with stupas and pillars, and with sending envoys and teachers. The details differ between sources and are treated carefully by historians. Around this time, and in the following centuries, Buddhism spread within India and into its northwest, and monastic centres grew up, including the great stupa complex at Sanchi.
Sites such as Sanchi, and later large teaching monasteries such as Nalanda, show how monastic life came to depend on royal and merchant support. Pilgrims were already travelling to the places of the Buddha’s life, and the stupas and shrines they visited helped give the faith a physical geography.
The southern route
Tradition holds that Buddhism reached Sri Lanka in the 3rd century BCE, associated with the monk Mahinda and the site of Mihintale. Sri Lanka became an important centre for preserving the Pali texts and for the community now called Theravada. From there, over many centuries and by uneven routes, forms of Buddhism took root in what is now Myanmar, Thailand, Cambodia and Laos, as well as in parts of maritime Southeast Asia. Early Southeast Asian Buddhism was often mixed with Hindu traditions and later Mahayana influences, and the later dominance of Theravada in the mainland region came gradually. This route is described in more detail elsewhere on this site, but the main point is that there was no single wave: it was a long series of contacts by sea and land.
The northern and Central Asian routes
Buddhism also moved northwest into Gandhara and across Central Asia. Merchants travelling the oases along the Silk Road Buddhism helped carry the faith, and monasteries and cave temples appeared along those routes. Monks translated texts from Indian languages into Central Asian languages and later into Chinese. The tradition usually places the arrival of Buddhism in China around the 1st century CE, though the first contacts were probably earlier and less formal.
From China, Buddhism reached the Korean kingdoms during the 4th to 6th centuries CE, and Japan during the 6th century CE, according to traditional accounts. In each country it combined with existing beliefs and political structures, developing distinct schools such as Chan (Chan Buddhism origins are debated), Seon, Zen, Pure Land and others. Dates given here are approximate and vary by source.
Tibet and the Himalaya
Buddhism came to Tibet from India, Nepal and China, with royal patronage in the 7th to 9th centuries CE being important in the usual account, followed by a second phase of transmission from the 11th century. This produced a Buddhism with a strong emphasis on Mahayana and Vajrayana ideas and on monastic institutions. From Tibet it spread into the Himalayan regions, Mongolia and parts of Russia and China. The standard narrative of how Buddhism reaches Tibet is simplified, as histories of this period were often written much later.
Decline in India and later movements
Over the later first millennium and into the second, Buddhism in much of India declined, for reasons that historians still debate, including changing patronage, competition with other traditions and political upheavals. Large monasteries such as Nalanda continued to attract students for several centuries, but the Buddhist presence in India was much reduced by the later medieval period. Interest in the ancient sites revived in the 19th century, when archaeologists and some Buddhist communities began to restore them.
In the modern era, Buddhism has also spread to Europe, the Americas and Australasia, through migration, through translation of texts and through teachers from many traditions. Today the religion has a worldwide presence, though the largest populations are in Asia.
What carried the teachings
Several kinds of people moved Buddhism across Asia. Monks and nuns travelled as teachers and translators, and some, such as the Chinese pilgrim monks who walked to India, returned with texts and relics. Merchants financed monasteries along trade routes and often became lay supporters. Rulers granted land and protection, and in some cases adopted Buddhist symbols and ideas in their own courts. Art and architecture also carried the message: stupas, cave temples, painted scrolls and statues allowed people who could not read the texts to meet the teachings. In every region, Buddhism adapted to local languages, customs and older beliefs, which is why a temple in Kyoto, Bagan or Lhasa can look so different from one in Sri Lanka.
Reading the history alongside the sites
A useful way to use this overview is to match each region with a type of place. Early India is represented by the places of the Buddha’s life and by stupa sites; Sri Lanka by ancient capitals and the sacred Bodhi tree; Southeast Asia by large pagodas and temple plains; Central Asia by caves and ruined oasis monasteries; East Asia by mountain temples and pagodas; and the Himalaya by monasteries, chortens and circuits walked on foot. Each reflects not only belief but also the patrons, materials and politics of its time.
A note on sources and pilgrimage
Almost every date above has caveats. Chronicles often reflect the aims of the communities that wrote them, and archaeology can support some details but not others. Treat any single tidy timeline with care. For travellers, the practical result is that pilgrimage sites in India, Sri Lanka, Southeast Asia, China, Korea, Japan and the Himalaya each reflect a different layer of this history, and local customs vary. Opening hours, access rules and conditions at the sites change, so check current official sources before travelling.