Revolutionizing Castles: Nobunaga’s Vision in Warriors Building Castles

The concept of castle changed with Nobunaga.

“Castles” are popular. There was a time when it was referred to as a trend, but events like the “Castle EXPO,” held annually in Yokohama, draw nearly 20,000 fans, showcasing its enduring appeal. Numerous books about castles have been published, most of which focus on the structures of fortifications, making them somewhat inaccessible to beginners. Historian Atsushi Kawai has released a book titled “Warlords Build Castles” (Poplar Shinsho), which takes a unique approach by discussing the charm of castles from the perspective of the warlords who built them. What were the thoughts behind the construction of these castles? What kind of warlords were considered masters of castle building? I spoke with Kawai.

Since ancient times, structures resembling castles have existed to protect living spaces, such as the moated settlements of the Yayoi period. In ancient times, there were also water castles in Dazaifu and mountain castles (Korean-style), and the residences of armed samurai can be considered, in a sense, castles. During the Nanboku-chō period of unrest, many mountain castles were built throughout the country, and during the Sengoku period, various daimyō constructed numerous fortifications within their territories. However, a person who significantly changed the concept of castle during the late Sengoku period was Oda Nobunaga. The characteristics of castles that began with Nobunaga and were inherited by Toyotomi Hideyoshi are said to be threefold.

“Firstly, the impressive stone walls, exemplified by Azuchi Castle, were constructed entirely of stone. Secondly, when building structures, they shifted from using post-and-beam construction to using large foundation stones to support the pillars. Thirdly, while buildings were previously thatched with reeds, they transitioned to tiled roofs.

On the other hand, some experts argue that Nobunaga was revolutionary in that the main keep and his residence were placed at the top of a hierarchical arrangement of his retainers’ houses. In any case, it’s undeniable that Nobunaga had a significant impact on the history of castles.”

 

 

With Hideyoshi’s unification of the country, the Nobunaga style spread nationwide.

During the Sengoku period, the design of castles varied significantly by region. While castles with stone walls and tiled roofs were common in Nobunaga’s domain, the Kanto region saw little use of stone walls. For example, the Hojo clan’s Odawara Castle was an earthen castle, and Tokugawa Ieyasu reportedly did not possess a stone-walled castle early in his career.

“However, as Hideyoshi inherited Nobunaga’s castle style and various regional warlords became his vassals, castles equipped with stone walls and keep towers began to spread. It was Nobunaga who first constructed a proper keep, but during his time, people truly lived there.

As the Sengoku period drew to a close, it became inconvenient to reside in the keep, and people began to settle in the main palace, which was more spacious and livable. The keep also evolved into a storage space or armory, and during the Edo period, there were instances where keeps burned down due to fire, and reconstruction was deemed unnecessary. Edo Castle is a prime example of this.”

Following Hideyoshi’s era, the construction of castles across the nation underwent significant advancements.

“For instance, the development of stone walls progressed greatly. In Nobunaga’s time, there was no technology to stack stones high all at once, so they built stone walls in tiers, known as dan-zukuri. However, over time, the ability to construct tall stone walls emerged.

They shifted from the ran-zumi method, which involved stacking natural stones and filling gaps with smaller stones, to the kirikomi-tsugi method, which involved shaping stones and fitting them together without gaps. The stone walls built by Kiyomasa are particularly notable for their impressive curvature and height, as well as their beauty.”

 

 

Who was the man who had the greatest influence on castles during the Edo period?

However, during the Edo period, as the country entered a time of peace, there were fewer opportunities for castles to evolve significantly. The role of castles shifted from being places of defense to serving as administrative centers. So, who is the person most credited with the history of castles?

“I believe the person who had the greatest influence on castles during the Edo period was Tōdō Takatora. He served Toyotomi Hidenaga and his brother Hideyoshi, and it’s likely that he honed his skills while watching and assisting in the construction of various castles. The person who made the most use of his castle-building techniques was Tokugawa Ieyasu.

As Ieyasu unified the country, he ordered many daimyo to construct castles in various regions. The design and construction of the castles for the ruler of the land were primarily undertaken by Tōdō Takatora. He was involved in many castles, including Kameyama Castle, Edo Castle, Sunpu Castle, and Nagoya Castle.

Takatora’s castles were characterized by high stone walls, wide moats, and a unique entrance design called masugata toraguchi. This masugata toraguchi entrance structure surrounded the enemy entering through the castle gate with stone walls and strong gates on three sides, allowing for attacks from above. He also developed the five-story keep and created a combined keep design that featured a large keep alongside smaller ones, as well as surrounding structures resembling longhouses (multiple gates) to establish an impenetrable defense. This type of castle construction became a foundational model for later designs. It’s clear how significant Takatora’s influence was.”

Furthermore, figures like Katō Kiyomasa and Katō Yoshiaki also constructed impressive castles. According to Kawai, their castle-building techniques were honed during the invasions of Korea.

 

 

“While enduring fierce battles in Korea, various innovations emerged, which significantly influenced their skills. Japanese warlords constructed many castles known as ‘Wajo’ in southern Korea. When they returned to Japan, they brought back the techniques they acquired and materials like Korean tiles to apply to their new castles.

However, it doesn’t seem that they directly adopted the castle-building techniques of Korea or Ming China. The distinctive tiled roofs show Korean influence, but the unique structures of the Wajo suggest that the Japanese warlords, gathered in one place, likely influenced each other.”

What was impressive about the castle-building masters?

So, what qualities made these military commanders, known as castle-building masters, so exceptional?

“They possessed knowledge and had a group of skilled engineers at their disposal. For instance, Takatora had senior vassals who specialized in castle construction. Having such experts among his subordinates was significant.

Kiyomasa Kato’s Kumamoto Castle features turrets named after his vassals, such as the ‘Iida-maru Five-Story Turret.’ He had his retainers construct them. However, there are records indicating that Kiyomasa provided very detailed instructions regarding the stone walls, so he was evidently well-informed himself, and the builders were also quite skilled.”

However, there are very few records regarding where they actually learned their castle-building techniques. It is believed that they likely learned by observing Hideyoshi during his construction projects or by being instructed to participate in those efforts, gradually developing their own skills and innovations. By the way, none of the buildings constructed by Hideyoshi still exist today (Osaka Castle was rebuilt by the Tokugawa after the fall of the Toyotomi clan), and only a few stone walls remain at Nagoya Castle in Hizen.

Tips for Beginners to Enjoy Castles

So, what are some enjoyable points for beginners visiting a castle?

“One of the easiest things to understand without much study is the stone walls. You can infer the era based on the way they are constructed, and if they’re high and have a curve, it indicates the style of Kiyomasa. It’s interesting to see differences in the construction methods between the original parts and the renovated sections. Unfortunately, most buildings, including those from the Edo period, have not survived, and only 12 keep the main tower still exist today. In that sense, the stone walls convey the essence of the time and are also quite easy to appreciate.

For example, the stone walls of Shirakawa Castle feature a section (called otoshi-zumi) that is constructed in a semi-circular arc, which is beautiful. Kanazawa Castle has a wide variety of stone walls, famous for its colorful stones that mix red and blue. Also, the stone walls leading up the stairs from the ‘Otemichi’ of Azuchi Castle, which have been excavated and restored, are breathtaking. And then there’s Kumamoto Castle. Although it is still under restoration, I think the curvature of the shinobi-kaeshi of the stone walls is truly impressive.”

Sometimes, it might be nice to take a moment to quietly gaze at the castle and reflect on the samurai warriors of the Warring States period.

The Warlord Builds a Castle” (Atsushi Kawai, author, Poplar New Book 263)