Lanka
The medieval period of Sri Lanka begins with the fall of Anuradhapura. In AD 993, the invasion of Chola emperor Rajaraja I forced the then Sri Lankan ruler Mahinda V to flee to the southern part of the country. Taking advantage of this situation, Rajendra I, son of Rajaraja I, launched a large invasion in AD 1017. Mahinda V was captured and taken to India, and the Cholas sacked the city of Anuradhapura. Subsequently, they moved the capital to Polonnaruwa. This marked the end of the two great houses of dynasties of ancient Sri Lanka, the Moriya and the Lambakanna. Following a seventeen year long campaign, Vijayabahu I successfully drove the Chola out of Sri Lanka in 1070, reuniting the country for the first time in over a century. Upon his request, ordained monks were sent from Burma to Sri Lanka to re-establish Buddhism, which had almost disappeared from the country during the Chola reign. During the medieval period, Sri Lanka was divided to three sub-territories, namely Ruhunu, Pihiti and Maya.
Sri Lanka's irrigation system was extensively expanded during the reign of Parākramabāhu the Great ( AD 1153–1186). This period is considered as a time when Sri Lanka was at the height of its power. He built 1470 reservoirs – the highest number by any ruler in the history, repaired 165 dams, 3910 canals, 163 major reservoirs, and 2376 mini reservoirs. His most famous construction is the Parakrama Samudra, the largest irrigation project of medieval Sri Lanka. Parākramabāhu's reign is memorable for two major campaigns — in the south of India as part of a Pandyan war of succession, and a punitive strike against the kings of Ramanna (Myanmar) for various perceived insults to Sri Lanka.
After his demise, Sri Lanka gradually decayed in power. In AD 1215, Kalinga Magha, a South Indian with uncertain origins, identified as the founder of the Jaffna kingdom, invaded and captured the Kingdom of Polonnaruwa with a 24,000 strong army sailed 690
