warfare between Sinhala kings, pretenders and foreign invaders from South Indian dynasties (the Cholas, Pallavas and Pandyas). These South Indian dynasties were strongly Hindu and often sought to eliminate Buddhist influence. In time, South Indian Buddhism was wiped out, and this severed a key cultural link between Sri Lanka and South India. This era of the conflict saw the sacking of Buddhist monasteries and often made the situation difficult for Buddhism. However, in spite of the instability, this era also saw the expansion of Buddhist culture, arts and architecture. By the 9th century, Buddhist monasteries were powerful institutions that owned property, land, estates, and irrigation works. They had been granted these estates by kings and generally hold them in perpetuity. Buddhist monasteries at this stage of Sri Lankan history were basically self-sufficient economic units protected by the Sinhala kings. These Buddhist establishments were also often plundered during times of internal strife by Sinhala rulers competing among themselves, such as during the reigns of Dathopatissa I (639–650) and Kashyapa II (650–659). Between the reigns of Sena I (833–853) and Mahinda IV (956–972), the city of Anuradhapura saw a "colossal building effort" by various kings during a period of peace and prosperity, the great part of the present architectural remains in this city date from this period. However, this was followed by the invasion and conquest of the Anuradhapura heartland by the Chola empire (between 993 and 1077), a war which devastated Anuradhapura and brought an end to the kingdom. The Polonnaruva era The Sinhalese in the south of the island (mainly the kingdom of Rohana) continued to resist, and the island was fully reconquered by Vijayabahu I (1055–1110) by 1070 who established the Kingdom of Polonnaruwa. The state of Sri Lankan Buddhism was so bad at this time that he could not find five bhikkhus in the whole island to ordain more monks and restore the monastic tradition; therefore, he sent an embassy to Burma, which sent back several eminent elders with Buddhist texts. Vijayabahu is also known for building the Temple of the Tooth. The next influential figure in Sinhala Buddhism was Parākramabāhu I (1153–1186) who unified the island and set out to reform the Sri Lankan Buddhist sangha. De Silva notes that this significant reform event was traditionally seen as the triumph of the Mahāvihāra and the repression of the other schools, but that "recent research has shown this