Alfred the Great's major achievement, and the one for which he recieved his honorific title, was to lead the Anglo-Saxon peoples of Wessex and other kingdoms in a series of campaigns against Danish invaders. He reformed Anglo-Saxon military practice, building a number of defensive outposts known as burhs, later called burghs.
This military reform led to fiscal reform. The lands around the burhs were organized into districts for the purpose of taxation, which local nobles were required to pay. He issued a uniform compendium of laws known as a domebook, which combined Roman law with traditional West Saxon law. He started schools associated with his court that sought to establish classical learning among West Saxon nobles, and encouraged a number of scholars from other lands to teach there. Alfred struggled throughout his reign to establish and maintain monasteries in the face of constant Danish assaults.