Óengus I of the Picts and Eadberht of Northumbria attack King Dumnagual III of Strathclyde, at Dumbarton Castle (modern Scotland). However, Eadberht's entire force is subsequently wiped out, probably by the Britons. King Cuthred of Wessex dies after a 16-year reign. He is succeeded by his distant kinsman Sigeberht. Abbasid Caliphate Ibn al-Muqaffa', Muslim writer and thinker, is tortured at Basra (modern Iraq), on orders from Caliph al-Mansur. His limbs are severed and he is thrown, still alive, into a burning oven (approximate date). Chinese Empire January 18 – An Lushan Rebellion: The eastern capital of Luoyang falls to the 200,000-strong army of the rebel general An Lushan, who defeats loyalist forces under Feng Changqing. The rebels cross the Yellow River, and march on to capture the cities Chenliu and Yingyang (modern Zhengzhou, Henan). Battle of Yongqiu: A Tang garrison (2,000 men), under Zhang Xun, successfully defend their fortress against the rebel army at Yongqiu. Zhang achieves a victory after a 4-month siege, and prevents the rebels from capturing the fertile Tang territory south of the Huai River. February 5 – An Lushan declares himself emperor at Luoyang, establishing a new empire, called the Great Yan. He pushes on towards the primary Tang capital at Chang'an (now Xi'an). An decides to seize southern China, to cut off loyalist reinforcements. Meanwhile, numerous soldiers join the rebellion. May – Emperor Xuan Zong hires 4,000 Muslim mercenaries to help defend Chang'an against the rebels. Loyalist forces take defensible positions in the mountain passes, but chancellor Yang Guozhong gives orders for them to leave their posts. July 7– An Lushan crushes the Tang troops at the Tong Pass, leaving the road to the capital wide open. July 14 – Xuan Zong flees the capital of Chang'an (along with the imperial court) for Sichuan, as rebel forces advance through the Tongguan Pass toward the city. Meanwhile, An Lushan is ailing, perhaps with diabetes. He is nearly blind and suffers from extreme irascibility. July 15 – Xuan Zong is ordered by his Imperial Guards to execute Yang Guozhong, by forcing him to commit suicide or face a mutiny. He permits his consort Yang Guifei to be strangled by his chief eunuch. An Lushan also has other members of the emperor's family killed. August 12 – Xuan Zong abdicates the throne after a 44-year reign. He is succeeded by his son Su Zong, as emperor of the