Japanese castles weren’t just for admiration but also for a safe home for the daimyo. The stone walls of castles made them fire resistant and effective to artillery attacks. The sloped walls could pose a problem from invaders climbing them, so stone dropping holes were created to prevent that. Spikes facing downward were also added to prevent invaders from climbing the walls. There were 3 main types of fortifications for castles: tojo, yamajiro, and ki. Tojo or grid pattern cities were the base for many Japanese castles. This method of fortification began during ancient imperial periods such as the Fujiwara and Naniwa. It later became the layout for cities like Nara and Kyoto. These bases were more of a government or political defense, with a ten-foot wall that would disappear further into the city. Yamajiro or mountain fortresses were very common in northern Kyushu. This method included rows of ritual stones called Kogoishi and earthworks and moats where mountains meet. Lastly, ki or palisade were semi permanent fortresses constructed on plains and plateaus. They were common in northern Honshu in the 7th and 9th centuries. They were mainly constructed to defend against the ezo tribes and control the surrounding area.    

All castles followed a common layout which had the keep at the highest point of the area they all used the surrounding area to build the castles. For example “Nagashino castle was built on triangular rocks where two rivers joined”(Turnball 150-151). Also “Takashima and Zeke used Lake Suwa and Lake Biwa respectively to provide water defense in a style called fujo or floating islands”(Turnball 150-151).  There were three common styles of Japanese castles: rinkaku, renkaku, and hashigogkaku. All of these styles were centered around the hon maru. The hon maru was the center of multiple courtyards or kuruwa that contained the keep. Surrounding the hon maru were the ni no maru (second courtyard) and san no maru (third courtyard). Rinkaku included the hon maru in the center with the ni no maru and san no maru in a concentric circle around the hon maru. Rinkaku was a very common building style that was used to build the Shizouka, Tanaka, and Osaka castles. The main reasons for using this style of building were that the walls and moats were long while the hon maru was small, making it easier to defend. Building in the rinkaku style required lots of labor and money as well. Renkaku was a style that had the hon maru in the center with the ni no maru and san no maru on either side. In renkaku, the hon maru needed extra protection because it was more exposed. Some castles built in this style were Mito and Sendai. Hasigokaku style could only be built in a yamashiro setting, which means mountain castle. The hon maru was built at the apex of the castle while the san no maru and ni no maru make a staircase up to the hon maru. The hon maru is exposed on one side to a lake, river, or cliff. Some examples of this style are Aizuwakamastu and Inuyama.

The process of building a castle took a long time and was labour intensive. The stone base of the castle was one of the most important structures in a castle. The bases allowed for heavier structures to built on top. The stone prevented soil erosion damage and was strong enough to hold up against the earthquakes. The Masons of Anou in Omi province specialized in stone structures. They used trigonometry to build the curved and sloped walls. The curved walls directed the stress on the walls. There are 4 main steps to building these stone bases. 

1. Hillside is carved

2. Ne shi (root stones) are laid down depending on the wooden supports

3. Construction of the curved walls with pebbles rammed in the outer wall

4. The wall is complete, and the moat is filled

When building a castle, the most important step was scouting the possible site of the castle. After the area was looked at, architects sketched out a layout on paper. Before construction started, a religious ceremony was held by shinto priests. “This consisted ritually of cutting the first sod within a sacred enclosure formed by fastening four ropes to four green bamboo poles”(Turnball 159-161). Gohei or streamers were then hung from the ropes and salt and rice were used as a ceremonial offering. Workers would be supervised while they worked and used the architect's plans. Sometimes if it was necessary they would use a relief model. A vertical groove would be dug to be used as guidance for the construction. To excavate the surrounding area two main tools were used: an adze and a basket tied onto a pole. Stones were carried in many ways, if they were smaller two people would carry it and if it was larger 4 people would wheel it over. If the stone was too large for the people to carry oxen would be used to wheel it over. A timber base would be used to guide the stone, this was used for the outermost wall where the stone followed a long timber and was secured by wooden stakes. The most important stone of a wall or base was called the ne shi or root stone. It made sure the wall was strong and durable, after the root stone was placed larger stones would be placed around it. After the stone base was created the gatehouse, towers, and keep could be constructed. The main material used for these structures was wood. A timber frame would be created and then a white plaster layer would be applied to the framework to make the outer surface. In the case of ‘black castles’ like Kumamoto, Matsue, and Okayama black painted wood would be used to make the outer surface. The final steps of building the castle were tiling, decorating, gliding, and putting on the golden sachi.

Bridges and gates were usually built at the entrance of the castles. The entrance in front of the castle was called ote or meeting place. The ote led to another gate called otemon. There were side gates called karamete, which means “the place where prisoners will be captured”(Turball 154-155). They were called this because they used these side gates to escape during a surprise attack. Gates would also act as a micro-defense system, with multiple gateways covering the entrance. The first gateway of a castle would lead to roads and would sometimes have roofs. The second gate was set up at a right angle to the first gate so if there was an invader, they would need to make a sharp turn. If the castle was built on a hill, the second gate would be placed higher; an example of this is Hikone castle. The gates were placed to form a square called masugata. There were also small secret gates called uzumi. The actual gates of the castle were made from heavy timber on heavy hinges and were reinforced by iron hinges and spikes.  Bridges were usually made from wood, other than the stone bridge built at Fukue Castle. Most wooden bridges “tended to be of cantilevered construction and could be very graceful”(Turnball 154-155). Hikone, Yamagata, and Matsumoto castles all had curved bridges, while Hachioji had a straight bridge. No drawbridges survived in Japan, but were recorded in drawings and descriptions. 

Another important structure of a castle was the walls. Walls, moats, and ditches usually split the kuruwa (courtyards) and the hon maru, which contained the keep. Smaller walls were placed upon stone bases, and the stones were placed in geometric arrangements. Behind the stone were two layers of pebble and smaller rocks that filled in the gaps. Some castles had walls 40 meters high, and small white plaster walls were placed at the top as openings. These openings were specifically designed for bows and guns. For example, a triangular opening would be used for guns, while a rectangular opening was used for arrows. The walls weren’t just for defense, though, as they were also used for aesthetic appeal. Behind these walls would be a row of planted trees; these acted as a shield against arrows and guns and would be an emergency source of timber in case of an attack. Trees were also planted in front of the outer wall to conceal the movements of the soldiers. 

Finally, the keep or tenshu was the most important structure in the castle.  Tenshu translates to “high heavenly protector” (Turnball 156-159). It is usually the first thing people see and is the highest point of the castle. They are usually 5-7 stories tall. 

Functions of a keep

1. “To provide a vantage point” (Turnball 156-159). 

2. “To act as the final line of defense” (Turnball 156-159). 

3. “To symbolize the daimyo’s power” (Turnball 156-159). 

4. “To provide secure storage” (Turnball 156-159). 

The first keeps that were built looked like the corner towers of a castle. The windows, gables, and roofs were built in an arranged pattern. The roof was built in an ornate pattern. The roofs were tiled and made of blue-grey tiles. There were two main styles for roofs: chidori hafu and kara hafu. Chidori hafu was a style with a triangular-shaped roof, and kara hafu was a style with a curved roof. The windows of a keep were square, but the windows on the top floor were made in a shape called katomodo. Older castles had keeps with thatched roofs, for example, Iwakuni Castle. The ridge at the top had a metal or tile sachi. The sachi was a tiger fish that was believed to fend off evil spirits and fires. Keeps were usually white and made of white plaster. Azuchi and Osaka castles are known to have bright colors and designs of dragons and tigers. ‘Black castles’ like Matsue and Okayama had keeps made of black painted wood. The mon or family crest was engraved at the apex. The ideal base shape was a rectangle, but some locations didn’t allow that, so that created an unusual base shape. An example of this is Wakayama Castle. Other castles made adaptations to create a rectangular base. For example, Kuramoto Castle’s first story overhangs the base to make a rectangle, and Bitchu-Matsuyama has stone walls integrated with the surrounding rocks to make the base.