In 1054 Lý Thánh Tông changed his kingdom's name to Đại Việt and declared himself an emperor. He married an ordinary girl named Lady Ỷ Lan and she gave birth to the crown prince Lý Càn Đức. In 1072 the infant Lý Càn Đức became Emperor Lý Nhân Tông (r. 1072–1127), the longest-ruling monarch in Vietnamese history. During the early years of Lý Nhân Tông, his father’s military leader Lý Thường Kiệt, uncle Lý Đạo Thành, and Queen Ỷ Lan became court regents. From the 1070s, border tensions between the Song Empire, local Tai principalities, and the Việt kingdom arose into open violence. In winter 1075, Lý Thường Kiệt led a naval invasion of southern China. Việt troops wreaked havoc on Chinese border towns, then laid siege to Nanning and captured it one month later. The Song emperor sent a large counter-invasion of Đại Việt in late 1076, but Lý Thường Kiệt was able to fend off and defeat the Song advance at the Battle of the Cầu River, where half of Song forces perished in combats and diseases. Lý Nhân Tông then offered peace with the Song, and later all hostilities were ended in 1084; the Song recognized the Việt polity as a sovereign kingdom. According to a fourteenth-century chronicle, the Đại Việt sử lược, the Khmer Empire sent three embassies to Đại Việt in 1086, 1088 and 1095. The matured Lý Nhân Tông came to rule in 1085. He defeated the Cham ruler Jaya Indravarman II in 1103, built the Dạm pagoda in Bắc Ninh in 1086, and constructed a Buddhist temple for his mother called Long Đọi pagoda in 1121. He died in 1127. One of his nephews, Lý Dương Hoán, succeeded him and became known as Emperor Lý Thần Tông (r. 1128–1138). This marked the downfall of Lý family’s authority within the court.