Complex sentence: The "Historia Brittonum", a 9th-century Latin historical compilation attributed in some late manuscripts to a Welsh cleric called Nennius, contains the first datable mention of King Arthur, listing twelve battles that Arthur fought.
Split into simpler sentences: The "Historia Brittonum" is a 9th-century Latin historical compilation attributed in some late manuscripts to a Welsh cleric called Nennius. It contains the first datable mention of King Arthur, listing twelve battles that Arthur fought.