In medieval England, a burh could be
- a fortification, usually high on a hilltop.
- a town.
The earliest burhs were fortifications, usually remote, not necessarily designed for extended occupation and certainly not meant to be permanent residences, as castles were. Then, in the ninth century, King Alfred the Great became involved in an extended war with invading Danes. During a lull in the conflict, Alfred strengthened his position by creating a royal Navy and by constructing numerous fortresses.
Some of these fortresses were based on old Roman fortifications that were repaired and rebuilt; others used the sites of bronze age forts. Still others were freshly-constructed earthen ramparts, covered with wood or stone, and fronted by deep ditchs. Alfred called all three types of fortress burhs.
Men from the villages in the area of each burh were required to defend and maintain that burh, usually on the basis of one man per hide contained in the village. Then, should any further Viking raids ensue, the people in those villages and the surrounding countryside could take refuge in the burh. Inside the walls of some of burhs, there was enough land to divide up into plots for residental purposes, usually in a gridwork. These burhs would evolve into towns.
After Alfred's susccessful defense of Wessex from the Danes, thanks to the burhs and other measures, he was able to unify much of England under his rule. Because many of the fortresses he had strengthened or constructed were now populated, the term burh came to mean a town. The word itself would evolve into "bury," "burg" and "borough."