The 9th century was a period from 801 (DCCCI) through 900 (CM) in accordance with the Julian calendar. The Carolingian Renaissance and the Viking raids occurred within this period. In the Middle East, the House of Wisdom was founded in Abbasid Baghdad, attracting many scholars to the city. The field of algebra was founded by the Muslim polymath al-Khwarizmi. The most famous Islamic Scholar Ahmad ibn Hanbal was tortured and imprisoned by Abbasid official Ahmad ibn Abi Du'ad during the reign of Abbasid caliph al-Mu'tasim and caliph al-Wathiq. In Southeast Asia, the height of the Mataram Kingdom happened in this century, while Burma would see the establishment of the major kingdom of Pagan. Tang China started the century with the effective rule under Emperor Xianzong and ended the century with the Huang Chao rebellions. While the Maya experienced widespread political collapse in the central Maya region, resulting in internecine warfare, the abandonment of cities, and a northward shift of population. West Africa Southeastern Nigeria Around the 9th century, the Edo people of what is now southeastern Nigeria developed bronze casts of humans, animals, and legendary creatures. These bronzes, which were used as vessels, amulets, pendants, and sacrificial tools, are among the earliest made bronzes ever found in Nigeria. Most items were part of a burial of a nobleman culture in the northern part of the Benin Empire. Evidence of long-distance trade between Benin and Portugal was also discovered through the thousands of glass beads found at Old Cairo at the workshops of Fustat. The development of the Benin Kingdom can be attributed to the proficiency at advanced metallurgy seen in the bronze jewellery crafted by local artisans. Ghana Empire The Ghana (Wagadu) Empire (before c. 830 until c. 1235) was located in what is now southeastern Mauritania and western Mali. It is considered the first of the Sahelian Kingdoms, which would exist in some form until the early 20th century. Western Europe Britain and Ireland Britain experienced a great influx of Viking peoples in the 9th century as the Viking Age continued from the previous century. The kingdoms of the Heptarchy were gradually conquered by the Danes, who set up Anglo-Saxon puppet rulers in each kingdom. This invasion was achieved by a huge military force known as the Great Heathen Army, which was supposedly led by Ivar the Boneless, Halfdan Ragnarsson, and Guthrum. This Danish army first arrived in Britain