Quan's forces were preparing to launch an invasion of Yi Province ruled by Liu Zhang, his general Zhou Yu fell ill and died in 209. Zhou Yu's successor Lu Su convinced Sun Quan to let Liu Bei "borrow" Nan Commandery in order to stabilize the situation on the western frontier. Meanwhile, Sun Quan established his capital at Jianye, in modern Nanjing. Sun Quan's attempts to capture territory north of the Changjiang ended in failure both in 208 and in 215. However, when he demanded the "return" of Nan Commandery from Liu Bei in 215, and was denied, Sun Quan moved west and occupied the commanderies of Jiangxia, Changsha, and Guiyang. In 217 Cao Cao made a major attack on the south. Despite failing to achieve any real gains, Cao Cao stationed a substantial army in the area, threatening Sun Quan's territory forcing Sun Quan to act as a figurative subordinate to Cao Cao. In 219 Sun Quan's general Lü Meng attacked Guan Yu's position in Jing Province on advice from Sima Yi during Guan Yu's attack on Fan Castle. Guan Yu was caught off guard and killed while the whole province fell under Sun Quan's control. Liu Bei retaliated in 221 but failed to make any headway and the invasion was defeated by Sun Quan's general Lu Xun. In 226 Sun Quan launched attacks towards the south and annexed Jiaozhou. In 229, Sun Quan declared himself emperor of Eastern Wu, creating the last of the Three Kingdoms. For the next 20 years, Sun Quan conducted several military campaigns in the north as well as an expedition to Taiwan in 230, but nothing ever came of these ventures. Noted for his longevity, Sun Quan was nevertheless unsuccessful as a military commander in comparison to his peers Liu Bei and Cao Cao. He died in 252 and was succeeded by his son Sun Liang. Demise After the death of Sun Quan, the dynasty became paralyzed by infighting. Sun Liang assassinated his guardian Zhuge Ke under the influence of a distant relative Sun Jun. When Sun Jun died in 256, he was succeeded by his cousin Sun Lin. In 258 Sun Liang sought to rid himself of his overseers but failed and was dethroned. He was replaced by Sun Xiu, sixth son of Sun Quan, then 22 years old. Sun Xiu staged a coup against Sun Lin and seized power for himself. Sun