of angering the Egyptian caliph Al-Hakim bi-Amr Allah, and is kept under house arrest from 1011 to 1021. During this time, he writes his influential Book of Optics. 1011: Under a new Rajah named Sri Bata Shaja, Butuan finally succeeded in attaining diplomatic equality with Champa after being denied in an older request made 4 years earlier to the Song dynasty court by sending the flamboyant ambassador Likanhsieh. 1014: The Byzantine armies of Basil II are victorious over Samuil of Bulgaria in the Battle of Kleidion. 1014: The Gaelic forces of Munster and most other Irish kingdoms under High King Brian Boru defeat a combined Leinster-Viking force in the Battle of Clontarf but Brian Boru is killed at the end of the battle. 1014–1020: The Book of Healing, a vast philosophical and scientific encyclopaedia, is written by Avicenna, Persian scholar. 1015: In the Battle of Nesjar in Oslofjord, Norway, the forces of Olav Haraldsson fought the forces of Sveinn Hákonarson, with a victory for Olav. 1018: The First Bulgarian Empire is conquered by the Byzantine Empire 1018: The Byzantine armies of Basil Boioannes are victorious at the Battle of Cannae against the Lombards under Melus of Bari. 1018: The Third Goryeo-Khitan War; the Korean General Gang Gam-chan inflicted heavy losses to Khitan forces at the Battle of Kwiju. The Khitan withdrew and both sides signed a peace treaty. 1019: Airlangga establishes the Kingdom of Kahuripan. 1020s 1021: the ruling Fatimid Caliph Al-Hakim bi-Amr Allah disappears suddenly, possibly assassinated by his own sister Sitt al-Mulk, which leads to the open persecution of the Druze by Ismaili Shia; the Druze proclaim that Al-Hakim went into hiding (ghayba), whereupon he would return as the Mahdi savior. 1025: the Chola dynasty of India uses its naval powers to conquer the South East Asian kingdom of Srivijaya, turning it into a vassal. 1025: ruler Rajendra Chola I moves the capital city of the empire from Thanjavur to Gangaikonda Cholapuram 1025: Rajendra Chola, the Chola king from Cholamandala in South India, conquers Pannai and Kadaram from Srivijaya and occupies it for some time. The Cholas continue a series of raids and conquests of parts Srivijayan empire in Sumatra and the Malay Peninsula. 1028: the King of Srivijaya appeals to the Song dynasty Chinese, sending a diplomatic mission to their capital at Kaifeng. 1020s: The Canon of Medicine, a medical encyclopedia, is written by Avicenna, Persian Muslim