Castles
...al mound (motte) and protected by one or more circular walls and often by a moat, the castle consisted of the keep, a wood or stone tower, and whatever accessory buildings were necessary for the housing of the castle retainers. These were situated in the bailey, the open area within the castle walls. In later the castles walls were topped by a parapet that could be manned during an attack. The Tower of London in an extant example of the motte and bailey castle. Its White Tower is the original Norman keep. From the 12th century, castle design was influenced by the Crusaders, who introduced improvements copied from Byzantine fortifications. European castles became larger, and there fortified areas increasingly complex. A fortified was might have separated the keep from the bailey. The keep itself was often a rectangular rather than a circular tower, with buttressed, parapeted walls and its own system of defense. Such large castles were often built on a height or into the side of a mountain. The largest could support town-sized populations and, with an assured water supply and adequate provisions, were virtually impregnable. With the invention of gunpowder, the castle lost its impregnability. Attacking artillery, out of range of the archers on the castle walls, could pour cannon shot into the heart of the castle and take it without even breaching the walls. Thus, by the 16th century, the medieval castle could no longer fulfill a defensive function, and fortified buildings were now erected only for military purposes. The architectural style of the castle, however, continues to be used for its imposing and often beautiful effects. In Japan, the great era of castle construction occurred in the late 1500s under the rule of the warlords Nobunaga and Hideyoshi (the Momoyama period, 1573-1615). In 1576, Nobunaga built a fortress city, Azuchi, whose central structure, a seven-story tower, was surrounded by the great houses of his courtiers, th...