sandalwood. He was appointed by Emperor Xuanzong (following the suggestion of Xuanzong's favorite concubine Yang Guifei and with the agreement of Chancellor Li Linfu) to be Jiedushi (regional military commanders) of three garrisons in the north—Pinglu, Fanyang and Hedong. In effect, An was given control over the entire area north of the lower reaches of the Yellow River, including garrisons about 164,000 strong. He took advantage of various circumstances, such as popular discontent with an extravagant Tang court, the synchronous Sogdian-involved Abbasid Revolution against the Umayyad Dynasty, and eventually the absence of strong troops guarding the palace coupled with a string of natural disasters. An Lushan was very influential in the Tang court, his close relationship with Emperor Xuanzong led to him being adopted by the imperial concubine Yang Guifei. The positions of power of Yang clan members (the family of the preceding Sui dynasty into which the Tang emperor had married) were important in this situation, especially complicated by the position of Yang Guifei's relative Yang Guozhong in the Tang governmental administration. Course of the rebellion The An Lushan Rebellion signaled a period of disorder spanning the reigns of three Tang dynasty emperors, beginning during the final (Tianbao era) period of the reign of Xuanzong (8 September 712 to 12 August 756), continuing through the reign of Suzong (12 August 756 to 16 May 762) and ending during the reign of Daizong (18 May 762 to 23 May 779), as well as spanning the four imperial claimants of the failed Yan dynasty. Revolt and capture of Luoyang At the end of 755 An Lushan revolted. On 16 December, his army surged down from Fanyang (near modern Beijing). Along the way, An Lushan treated surrendered local Tang officials with respect. As a result, more and more of them joined his ranks. He moved rapidly along the Grand Canal and captured the "Eastern Capital" city of Luoyang on 18 January 756, defeating the poorly supplied General Feng Changqing. There, on 5 February, An Lushan declared himself Emperor of the new Great Yan dynasty (大燕皇帝). His next steps would be to capture the Tang western capital of Chang'an and then to attempt to continue into southern China to complete his conquest. Battle of Yongqiu However, the Battle of Yongqiu, in the spring of 756, went badly for An Lushan. Although his army, under Linghu Chao, was numerous, it was unable to make