Old English developed as a language between 450-1150 AD during the Anglo-Saxon period of English history. The Germanic tribes of the Jutes, Angles, and Saxons invaded Britain and their language merged with the Celtic languages that were already spoken there to form Old English. Several important works of Old English literature were produced, most notably the epic poem Beowulf, which describes Germanic social conditions and ideals. Christianity was also introduced during this time which brought writing and literature to England.