fight a border war, with Vietnamese forces striking first on land and with their navy, and afterwards Song armies advancing as far as modern-day Hanoi, the capital, but withdraw after Lý makes peace overtures; in 1082, both sides exchange the territories that they had captured during the war, and later a border agreement is reached. 1076: the Ghana Empire is attacked by the Almoravids, who sack the capital of Koumbi Saleh, ending the rule of king Tunka Manin 1076: the Chinese Song dynasty places strict government monopolies over the production and distribution of sulfur and saltpetre, in order to curb the possibility of merchants selling gunpowder formula components to enemies such as the Tanguts and Khitans. 1076: the Song Chinese allies with southern Vietnamese Champa and Cambodian Chenla to conquer the Lý dynasty, which is an unsuccessful campaign. 1077: the Walk to Canossa by Henry IV of the Holy Roman Empire. 1077: Chinese official Su Song is sent on a diplomatic mission to the Liao dynasty and discovers that the Khitan calendar is more mathematically accurate than the Song calendar; Emperor Zhezong later sponsors Su Song's astronomical clock tower in order to compete with Liao astronomers. 1078: Oleg I of Chernigov is defeated in battle by his brother Vsevolod I of Kiev; Oleg escapes to Tmutarakan, but is imprisoned by the Khazars, sent to Constantinople as a prisoner, and then exiled to Rhodes. 1078: the revolt of Nikephoros III against Byzantine ruler Michael VII 1079: Malik Shah I reforms the Iranian Calendar. 1079: Franks start to settle around the Way of Saint James (Today, modern North Spain) 1080s 1080–1081: The Chinese statesman and scientist Shen Kuo is put in command of the campaign against the Western Xia, and although he successfully halts their invasion route to Yanzhou (modern Yan'an), another officer disobeys imperial orders and the campaign is ultimately a failure because of it. 1081: birth of Urraca of León and Castile future Queen of Castille and León. 1084: the enormous Chinese historical work of the Zizhi Tongjian is compiled by scholars under Chancellor Sima Guang, completed in 294 volumes and included 3 million written Chinese characters 1085: Alfonso VI of Castile captures the Moorish Muslim city of Toledo, Spain. 1085: the Katedralskolan, Lund school of Sweden is established by Canute IV of Denmark 1086: compilation of the Domesday Book by order of William I of England; it was similar