As castle design evolved, the great tower was eventually replaced by walled enclosures, which permitted more effective use of troops and better livin… - Marilyn Stokstad

Castles were more than military posts; they were the centers of political and economic power. As government headquarters they were built to impress the local population as well as visitors and rivals. While power was spread among great tenants-in-chief in a system of delegated government, castles in each territory were places where local lords collected taxes, settled disputes, and administered justice.

Richard the Lion Hearted, who became king of England in 1189, had inherited Aquitaine (western France) from his mother Eleanor and Normandy and Anjou—and England—from his father Henry. As Duke of Normandy and Anjou, Richard was a vassal of the king of France, but he controlled more land in France than did the French king. Although Richard had been an ally of Philip Augustus in the Third Crusade, in 1192 he went to war with the king over his French lands. Richard built Chateau Gaillard (he called it the “cocky castle”) on a cliff above the Seine north of Paris to defend his claims to Normandy. (...) Richard chose an excellent site, in the territory of the archbishop of Rouen, who objected strenuously until Richard paid him a handsome sum for the land. (...) Richard also raised money by selling rights of citizenship to residents of the town.

When a strong central authority protects borders and reduces internal crime, people have little need for fortified dwellings, although the rulers may build walls and towers to define legitimate residents and defend the country against external threats. When central authority breaks down, however, individuals are more likely to fortify their homes. The presence of castles in the landscape indicates a decline in stability and peace.