Alfred was also known as the "Great King of the West Saxons." He reigned 871-899 and prevented the Danish conquest of England, defeating them at Edington(878) after a campaign of guerrila warfare. After his victory he allowed the Danes to keep their conquests in Mercia and East Anglia provided that Guthrum, their King, was converted to Christianity. Alfred built a navy of Warships to defend the south coast against further Danish invasions (885-86; 892-96) and protected Wessex with a chain of fortifications. He took London and made it the capital (886), thus gaining control of all England except the Danish areas. He is considered the greatest English King and the founder of England's Civilization and Nationality. He wrote the Anglo-Saxon Chronicle the first written history in a modern language and founded Oxford University.