The Sinhalese withdrawal from the north is sometimes attributed to the cumulative effect of invasions from southern India (a rationale that has been exploited against the Tamils in modern Sinhalese politics). This interpretation has obvious weaknesses because after each of the south Indian invasions of the preceding centuries, the Sinhalese returned to the dry zone from the hills and repaired and revived the ancient irrigation system. K.M. de Silva suggests that the cumulative effects of repeated invasions "ate into the vitals of a society already losing its vigour with age." A civilization based on a dry-zone irrigation complex presupposes a high degree of organization and a massive labor force to build and maintain the works. The decline of these public works mirrored the breakdown in the social order. Another factor that seems to have retarded the resettlement of the dry zone was the outbreak of malaria in the thirteenth century. The mosquito found ideal breeding grounds in the abandoned tanks and channels. (Malaria has often followed the destruction of irrigation works in other parts of Asia.) Indeed, all attempts at large-scale resettlement of the dry area in Sri Lanka were thwarted until the introduction of modern pesticides.

During the thirteenth century, the declining Sinhalese kingdom faced threats of invasion from India and the expanding Tamil kingdom of northern Sri Lanka. Taking advantage of Sinhalese weakness, the Tamils secured control of the valuable pearl fisheries around Jaffna Peninsula. During this time, the vast stretches of jungle that cover north-central Sri Lanka separated the Tamils and the Sinhalese. This geographical separation had important psychological and cultural implications. The Tamils in the north developed a more distinct and confident culture, backed by a resurgent Hinduism that looked to the traditions of southern India for its inspiration. Conversely, the Sinhalese were increasingly restricted to the southern and central area of the island and were fearful of the more numerous Tamils on the Indian mainland. The fact that the Hindu kingdom at Jaffna was expending most of its military resources resisting the advances of the expansionist Vijayanagara Empire (1336-1565) in India enhanced the Sinhalese ability to resist further Tamil encroachments. Some historians maintain that it was the arrival of the Portuguese in the sixteenth century that prevented the island from being overrun by south Indians.

Foreign rulers took advantage of the disturbed political state of the Sinhalese kingdom, and in the thirteenth century Chandrabhanu, a Buddhist king from Malaya, invaded the island twice. He attempted to seize the two most sacred relics of the Buddha in Sinhalese custody, the Tooth Relic and the Alms Bowl. In the early fifteenth century, the Ming dynasty Chinese interceded on behalf of King Parakramabahu VI (1412-67), an enlightened monarch who repulsed an invasion from the polity of Vijayanagara in southern India, reunited Sri Lanka, and earned renown as a patron of Buddhism and the arts. Parakramabahu476 hu VI was the last Sinhalese king to rule the entire island.

During this extended period of domestic instability and frequent foreign invasion, Sinhalese culture experienced fundamental change. Rice cultivation continued as the mainstay of agriculture but was no longer dependent on an elaborate irrigation network. In the wet zone, large-scale administrative cooperation was not as necessary as it had been before. Foreign trade was of increasing importance to the Sinhalese kings. In particular, cinnamon--in great demand by Europeans--became a prime export commodity. Because of the value of cinnamon, the city of Kotte on the west coast (near modern Colombo) became the nominal capital of the Sinhalese kingdom in the mid-fifteenth century. Still, the Sinhalese kingdom remained divided into numerous competing petty principalities.

Data as of October 1988