This era of 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 who owned property, land, estates, and irrigation works. They had been granted these estates by kings and generally held 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).