Overview of Castles
Castles were basically military structures built for regional defense against "outsiders" during periods of violent strife. The oldest types of Japanese castles were called ki (e.g., in 7th century northern Kyushu) or saku (in Japan's northeast). These were fortified with earthen foundations, stone walls and/or wooden palisades. In the medieval era, so-called "mountain castles" (yamajiro), built with great attention to defense and using to advantage the natural contours of mountainous areas, were built in many parts of the country.
In the 16th century era of exacerbated strife, various new factors came into play, including changes in fighting techniques brought about by the use of guns. Castles became symbols of the "glorious exploits" and authority of territorial overlords who had gained control over one or another region, and there developed the custom of residence by a considerable number of people within castle walls. Allied with these trends was the building of high towers dominating the central portion of castle compounds. With the development of these trends, castles became classified into so-called hirayamajiro (e.g., Himeji Castle), which made use of natural hills, and so-called hirajiro (e.g., Matsumoto Castle), built on level ground. In both cases, distinctive types of towns, known as jokamachi, were built in the areas immediately adjacent to the castles.
After the 16th century, the more important castles typically consisted of a so-called hommaru area in the center, occupied by a tower-like structure (tenshu) and the residence of the castle lord, surrounded, in a concentric or spiral-like fashion, by areas known as ninomaru and sannomaru, as well as so-called kuruwa areas occupied by storehouses and the houses of feudal retainers. Each of these areas was surrounded by stone ramparts and so-called tamon-yagura towers fortified by devices for hurling stones and having small "windows" known as yazama and teppozama through which arrows could be shot and guns could be fired. In the corners of each of these areas were watchtowers known as sumi-yagura. The tower-like tenshu structure in the hommaru area was at first an independent building, but it gradually developed into a compound structure with smaller annexes known as kotenshu. In the case of the Himeji Castle, the main tenshu was connected by a complex structure to 3 kotenshu annexes which included within them cooking facilities for a large number of people in case the castle came under long-term siege. The central tenshu structures often had 5 or 6 storeys. In the 17th century their outer walls were covered with a whitewashed cement-like overlay, which replaced black-painted wooden boards.
