Wikipedia
Pannai, Panai or Pane is a Buddhist kingdom existed around 11th to 14th century located on east coast of Northern Sumatra. The kingdom was located on the Barumun River and Panai River valleys, today located in Labuhan Batu Regency and South Tapanuli Regency, North Sumatra, Indonesia. Because of the scarcity of inscriptions and historical records, this kingdom is among the mysterious and least known polity in Indonesian history. Historian suggested that the Pannai kingdom was probably a principality or a vassal allied under the Srivijayan mandala and later to Dharmasraya kingdom. The historical records mentioning this kingdom can be found from Indian and Javanese sources.
Despite the lack of local historical records, on the upstream of these rivers however, 16 Buddhist Vajrayana temples were discovered. These temples today are known as Padanglawas temple compounds, one of them are Bahal temple. Experts suggest that the existence of the temples is related to the Kingdom of Pannai. The temples is the traces of Vajranaya Buddhism in Sumatra. The place is most probably a religious-complex for warrior-monks of and had a key role, being located mid-way in the Strait of Malacca in policing the trade within the area and repelling invading forces as well as providing spiritual guidance to any pilgrim from China, India or within the archipelago.
The state of Pannai, according to inscriptions found in India, fell after a surprise attack from the rear. Pannai did not suspect an attack from a Chola occupied Srivijaya, the mandala's capital.
Panay island in the Philippines is said to have been named after the state of Pannai, of which Visayan (descendants of Srivijayans) oral legends recount that their 10 Datus or Datuks (in Malay) that transited from Borneo, rebelled against the Rajah named Makatunao. Thus, mirroring the situation in Pannai-proper which was fell by the Hindu Chola dynasty, to which, the datus of the Visayan legend, the Maragtas, refused to bow to. Instead of bowing to the Maharajah's and his puppet rajah's domination, set out to other islands, together with their constituent nobles, soldiers and scholars. The Kedatuan of Madja-as may be thus considered as the successor-nation to the Pannai-state, as the Pannai itself underwent dissolution as it was attacked and eventually annexed by the Hindu Majapahit Empire.