Above is an example of the Rinkaku Style from the Shizuoka castle
A primary aspect that all castles shared was the strategic placement of a castle over/on a topographical region such as mountains, hills and rivers. These aspects helped a castle stay untouchable by enemies and give it a unique look. But all castles have a few things in common including the Kuruwa which is a system of many courtyards and enclosed spaces. The center of the Kuruwa was the "hon maru" (main bailey) which contained the keep (Turnbull, Strongholds of Samurai 14). There are 3 different styles in the arrangement of the Kuruwa.
Rinkaku Style- (left) has a hon maru in the center of the castle, a ni no maru and a sin ni maru arranged in concentric rings. This layout is great for defense but the area this layout takes up is very big and can cost a lot of money and resources to construct a Rinkaku style Castle, so they were very uncommon. The Tanaka, Shizuoka and Osaka castles are the closest approximations to this style (Turnbull, Strongholds of Samurai 14).
Renkaku Style- has the hon maru in the center, the ni no maru and the son nu maru on either sides. This offered little defense of the hon maru (exposed). The Mitu and the Sendai castles are example castles of the Renkaku Style (Turnbull, Strongholds of Samurai 14). Hashigokaku Style- this can only apply to a "Yamashiro" (mountain based) castle. The hon maru is at the apex, from there the ni no maru and the son no maru descend like steps. In large castles there would be even more protection with the three maru but then be encircled by 2-3 more for extra protection. This creates a maze of interlocking walls and gates which confuse the enemy (Turnbull, Strongholds of Samurai 14).
Castle Wall
This shows the stone base (bottom) and the plaster wall (top) with measures 30-40m
A large part of the great defense a Castle has is it's advanced and enigmatic wall layout. The Kuruwa and the maru were divided by moats, ditches and 2 walls- the small wall on top of the stone base and the massive base (wall). The stones of the wall (stone base) are very strategically placed so that each stone fits perfectly creating a compact solidness. Behind the primary layer of stone there are 2 layers of pebbles. The stone base could measure to be up to 40m. The Castles foundation is a series of stone bases holding up structures which are linked together by housed low walls. Walls were designed to resist earthquakes (Hitchcock, 3) The stone base is a great defensive aspect and the smooth plaster wall on top of the stone base wall has triangular cut outs in it for guns and arrows. The Hemeji and the Kumamoto walls are virtually impenetrable. Minor small walls are buttressed and usually there are rows of pine trees in front. These walls make the Castle complicated to navigate by a foreign eye.
Bridges and Gates
In order for a Castle to be secure it has to have interior and exterior monitoring of what comes in and goes out. Gates and Bridges allowed Japanese Castles to be more secure and to establish order within the castle. Ote was the entrance at the front of the castle and that was protected by the otemon (front gate). Postern gates where used as "sally parts" for surprise attacks. Bridges were usually made of wood (except for the Fukue castle which had stone bridges). Fixed wooden bridges tended to be cantilevered with a beam. Draw bridges were very uncommon in Castles. A gatehouse was the first structure that anyone encountered inside the castle. The gatehouses had micro-systems of defense where a pair of gates covered an entrance. At some times there were many rows of gates to ensure maximum security. Even along some walls were secret gate entrances.
Castle Keep
Above is a picture of a main tower or keep
The "Tenshu Kaku" or keep was the largest and most elaborate of the towers. A keep would range from 3 stories to 7 stories. The purposes of a keep are to:
Provide a vantage point
Act as a final line of defense
Symbolize the daimyo power
Provide secure storage space
The keeps however where very ornate structures, resembling corner towers. These made dramatic statements of a daimyo's power with their large imposing size and their lavish architecture. The keeps had palisades and gardens at the top of walls surrounding the Keep meaning to show the daimyo's wealth and to also protect the Keep from spies. It was a very complex structure. The roof was often designed with chidori hafu (triangular shapes) and kara hafu (curved with an apex) (Turnbull, Strongholds of Samurai 14). The roofs where always tilted with blue-grey tile. Osaka and Azuchi castles are known for their bright colored keeps with representations of tigers and dragons. The Keep was also confusing from an outside perspective since the layout outside did not match internal layout. For example, the second floor can look like the third floor from the outside, which tricked invaders. (Japanese Castle Architecture- 4) The windows where square and on the upper most story they were ornate koto modo windows with a balcony. The Keep is where the people of the castle would go in case of a siege or a infiltration of the castle. Most of the time this would be the sight for daimyo and other high leaders to do seppuku. (Japanese Castle Architecture- 4) The keep had food and water to last for a long time but eventually "when they can no longer hold out, they kill their women and children" (- Jesuit Joao Rodriguez) and then burn down the keep.
Defensive Layout of a Japanese Castle
Above is a stone path way that leads to the front gate. Walls surround the castle
The architecture of the castle was elegant and deadly for military function. The foundation and location of a castle is mainly based off of a defensive point of view from the castle. For example, the geographical location helped people in the fortress see where enemies came from so they knew how to prepare to defend the castle. Most castles were built on a yamashiro (mountain) scheme, because they would be able to see enemies approaching from a distance. It also made the castle look more intimidating/impressive from a distance. (Japanese Castle Architecture- 4)There is also the hirashiro (flat plain) and hirayamashiro (lowland hills) schemes which weren't uncommon and were better if you wanted to build a more permanent castle. (Japanese Castle Architecture- 4)Once you had the foundation of the castle, the steep walls around the castle and the deep moats would be very important for defending and attacking enemies. These walls didn't necessarily cover all of the castles surrounding buildings, but did play an important role. The walls and gates that surrounded the castle were built in a type of maze. The castle designers wanted the attackers to move in a path that was anticipated. In the path these attackers went in, the walls had many holes, windows, and platforms formed from planks so the castle could attack their incoming enemies. (Japanese Castle Architecture- 4) With these holes in the walls, there would be rocks, hot sand, and other deathly items being thrown down. They would have archers and gunmen ready to fire at the "stone throwing shelf", have caltrops scattered, bamboo spikes facing diagonally to spike into enemies, and even have trees so the attackers run pass them like an obstacle. (Japanese Castle Architecture- 4)These gates and walls were narrow and every turn would force you to turn in a bottleneck effect, slowing you down. You would have to follow this maze all the way until you got to the center of the castle. (Japanese Castle Architecture- 4) And in the towers around the palace they sometimes suspended logs from ropes to hit their enemies.
European vs. Japanese Castles
Since during the Middle Ages of Europe went through a feudal system, they also made many castles as well that had many similarities to the ones during this period. many of these similarities are in the architectural and defensive ideas on the castles. Some of these similarities are:
Having large & tall walls for protection
Having moats around the walls to discourage digging tunnels
Having narrow and steep stairways to make assaults difficult
Having port holes for guns and arrows
Having a main gate area and using it as a trap
usually having concentric rings of walls to give themselves multiple layers of protection
Capitalizing on the geographical features around them