Edo Castle Stone Quarries
The Stone Quarries and Kokuin of Edo Castle
Everyone, well most Jcastle geeks that is, has marvelled at the immense stone walls of castles like Edo Castle, Osaka Castle, and Nagoya Castle. But, have you ever really thought about how they were built? Where did all that stone come from? It wasn't just found on the site. Who actually built those walls? Stone pilings were used to prevent erosion and to strengthen earthen embankments for a long time. Big stone walls were built by Nobunaga and Hideyoshi, but the Tokugawa took that to a whole new level building bigger and more vast walls than had ever been attempted before. Big keeps, beautiful gates and towers (yagura) may be magnificent to behold, but the strength of any one castle really comes down to it's network of moats and walls.
After years of war and strife an unstable peace was brought to Japan with the founding of the Tokugawa Bakufu. In order to maintain that peace (and their control) the Tokugawa kept all regional daimyo too busy to war with a series of infrastructure projects called Tenkabushin. Constructing castles for the Tokugawa was the most famous example, but there were also a number of other projects around the country to improve roads, river ways and some temples and shrines. At some point it came to be called "tenkabushin", perhaps to emphasize the role in the Tokugawa's master plan to control all Japan, but at the time they were simply called 公儀御普請 (Kougi go-fushin) or 手伝普請 (tetsudai fushin), basically "public infrastructure projects". Sankin Kotai, which is often cited as a way for the Bakufu to force daimyo to spend a lot of money preventing them from raising armies, actually began in 1635 after the stone wall construction of Edo Castle was nearly complete (1604-1636).
The castles built under the tenkabushin umbrella are listed below:
If you consider this a network of castles controlled by the Tokugawa, it's also a giant wall of defensive structures around central Japan (with a few exceptions for Tokugawa strongholds in the East). The role of these castles was to prevent the western daimyo who were defeated at the Battle of Sekigahara from rebelling or making any major incursions into the rest of Japan and Tokugawa held territories.
Many of the Tenkabushin castles listed above are also famous for their impressive and extensive stone walls. Stone walls were such an important feature of Tokugawa castles that they established a group of specialized stone wall builders, called the 公儀穴太頭 Kougi anoutou. They were drawn from the anoushuu (穴太衆) stone wall building masters of the Omi Domain (in Sakamoto) that caught Tokugawa's attention for their work on Hideyoshi's Osaka Castle. They did not necessarily build the walls but directed their construction at all these castles.
The rest of this article describes the building of stone walls for Edo Castle, but parts of the story are applicable to many others.
Stones for Edo Castle 〜石材〜
Look at the photos below. Notice the white stones on the corner of the left photo compared to the darker stones behind. While walking around Edo Castle, I've mistakenly heard people think the white stones must be concrete to replace ones that were broken or were damaged in the war. Actually, the white looking stones are a different type of stone called kakogan (granite) as opposed to the darker ones which are andesite (anzangan). The second photo shows the Edo Castle main keep foundation which is a combination of bright colored granite with a few andesite stones in the front. The last photo is of Osaka Castle which uses much more granite because it is more readily available around the Osaka area. In the case of Edo Castle, the granite blocks are used on the corners because they are marginally harder than the andesite.
The andesite, which has a wide variety of differing characteristics that make it possible to identify the place it came from, is from the Izu Peninsula. The source of the granite, on the other hand, is harder to identify. Some of the white stones at Edo Castle come from islands in the Seto Inland Sea. Stories say the beautiful white stones were brought all the way from the Seto Inland Sea to impress the Shogun. Some granite may have also been brought from granite locations near Edo like Gunma and Tochigi. The granite for the main keep foundation you see today (4th main keep, never built) was brought by Maeda Tsunanori from Inujima (Okayama Pref) in the Seto Inland Sea.
Stone Wall Construction at Edo Castle 〜石垣普請〜
The construction of Edo Castle's magnificent stone walls began in 1604 and lasted through three Tokugawa Shoguns (Ieyasu, Hidetada, Iemitsu). The Tokugawa utilized most of the daimyo to some extent to build the stone walls of Edo Castle over roughly 30 years. The Western Daimyo tended to get the more labor intensive and more expensive jobs while allies got lighter duties.
Assignments were split into two major types:
Moat Construction (堀方/horikata): Typically, the Eastern daimyo were responsible for digging the trenches, moats and creating the foundation for stone walls.
Stone Wall Construction (石垣方/ishigakikata): Typically the Western Daimyo, were responsible for quarrying the stone and building the walls. Under the third Shogun Hidetada, this was further broken down to those responsible for stone quarrying (寄方/yosekata) and those building the walls （築方/tsukikata）
The image below shows diagrams of parts of the outer moat. The diagram on the left displays assignments for creating the moat foundation by the Horikita daimyo. The image on the right shows those daimyo responsible for creating the stone walls. This section of the outer moat was completed in the third phase of construction (1635-1637). Click the photo to enlarge it for more detail.
The first round of stone wall construction at Edo Castle lasted from about 1604-1606 involving 28 of the Western daimyo. In just over 2 years, the first walls of the Honmaru, Ninomaru, and Sannomaru were completed. Some of these well-known daimyo; including Kato Kiyomasa (Kumamoto), Maeda Toshimitsu (Kanazawa), Mori Hidenari (Hagi), Ikeda Terumasa (Himeji), Horio Yoshiharu (Matsue), Fukushima Masanori (Hiroshima), among others got very good at building huge stone walls in a short time and went on to build their own impressive castles in the same manner. The Maeda took this concept of dividing up the responsibilities for the vast walls of Kanazawa Castle. That's why you'll see many kokuin there too.
The photos of the following screens are from the stone wall exhibit at Ichigaya Station in Tokyo. The illustrations depict the construction of stone walls at Sunpu Castle but the concept is the same. Enlarge the photos and look closely to see various scenes of carrying stones and building walls.
Stone Quarries 〜石丁場〜
Ishigakikata daimyo were assigned to areas of Izu to quarry the stone, but had to find and lay claim to their specific quarry sites. The stone was cut, shaped and then transported to ports along the coast. The stone was shipped by boat from these ports to Edo. Once they arrived in Edo, the stone was offloaded and again transported overland to each daimyo's stockpile which was sometimes their own Edo residences. In fact, the daimyo in charge of gathering stone were not allowed to use stone in building their own residences until they filled their quotas. Throughout this process, the daimyo themselves were responsible for acquiring (building, buying or borrowing) the ports, ships, and locations to stockpile their stone.
Boundary Marker Stones 〜標識石・境界石〜
The stone quarries were very close to each other and you may see several on a single mountain. The individual quarries were marked off by large boundary marker stones (境界石) indicating the borderline between quarries. These may have been marked with a single large kokuin on a large stone, several stones lined up with kokuin in them, or the name of the daimyo carved. A few large stone with the daimyo's name have been found centrally located in quarries too.
Stone Splitting 〜石割り〜
Before splitting a stone, dotted draft lines are carved into the stone to mark how it should be cut. Ya-ana holes (arrow holes, wedge holes) are then carved along the line to prepare the stone for splitting. Since stones are typically split along the dotted lines, it is quite rare to see such a line remaining on any stone, but there are several at the Heda Stone Quarry
The actual splitting of the stone used a couple techniques. In the illustration on the left, a block of dried wood was placed in the hole. Water poured into the hole would cause the wood to expand and split the stone. In the second method, metal wedges were hammered into a stone to split it. People who study stone walls often look at the size of these wedge holes/ya-ana to guess how it was split and when. The wood method is thought to be a little older and required larger wedge holes, but obviously both techniques are used throughout the quarries for Edo Castle.
The illustration below shows how large blocks were cut from the bedrock to be further split and shaped into rectangular corner stones for the stone walls. The photo on the right shows the ruins of almost the exact same scene 400 years later. This site is the only such scene that I've personally found. It's an amazing find because you can easily imagine how a big block was cut away just like in the illustration. This must have been early in the process of mining a quarry so it is natural that few, if any, other such sites remain.
Transporting Stones 〜石の運搬〜
Stones were transported to the ports pulled on a sledge (修羅 shura).
If you happen to find what looks like a well worn trail along the edge of a stone quarry, it may have been what's called an ishibikimichi/ 石曳き道 (stone pulling trail), also known as a "sledge trail" (修羅道 shuramichi), that was used to transport the stone to ports. As mentioned earlier, there were often multiple quarries closely grouped together or on the same mountain. These trails were often shared between the quarries they bordered.
In the left photo below you see a map of Izu with some of the main quarry areas highlighted with orange dots. The lighter green shades are areas with good andesite stone. The green line along the coast also indicates the route to Edo. The second photo illustrates loading large cornerstones onto a boat. Only 2 of these large stones could be loaded on a single boat. The large cornerstones are also known as "100 Man Stones" (百人持ち石) because it took a 100 men to move them. At the peak, 3000 boats per day were making the trip twice a month. It may have been easier than transporting stone over land, but it was by no means safe. Many boats sunk in the process and to this day you can still see stones that were bound for Edo Castle on the bottom of the sea.
Each daimyo who was assigned to quarry stone was also given a quota based on the size of their domain. As the stones were cut and prepared for shipping to Edo, the stones were marked with the daimyo's sigil or other marking so that the Tokugawa officials could tabulate how much stone was provided and make sure the daimyo met their quotas. These marks, called kokuin, also served to prevent other daimyo from stealing previously cut stones or laying claim to another daimyo's stone. Quarrying such stone is hard dangerous work. Even if it wasn't sanctioned by the daimyo, it is possible that the workers may have laid claim to another daimyo's stone given the opportunity. I read in one account of the Ohkawa Yato-no-iri Stone Quarry that there were so many injuries that the stream through the quarry was often tinged red with blood. Kokuin are sometimes mistakenly thought to be the kamon (family crest) of a daimyo but that is not always the case. The kokuin may be that of a retainer, it may indicate a specific quarry, or it may be the foreman in charge of the quarry. Unfortunately, it can be difficult to connect a kokuin to a specific daimyo. The same marks were used by different daimyo in different areas and times. The best way to connect a daimyo to a kokuin and specific quarry is actually through historical accounts.
Markings on the stones of stone walls are often put into one broad category called kokuin, but not all kokuin had the same purpose. In addition to the markings mentioned above, you will also find other markings on stones that were made at the ports or in tabulating quantities, marks used by the builders during construction of the walls, daimyo names, and even symbols or words meant to protect the castle.
Back at the castle, you can see kokuin all over Edo Castle if you know where to look. The first thing to note is that not every stone will have a kokuin. Some have been erased by time and weathering, some were simply not on the outside face of the stone, and some stones were also reshaped on site. Futher, kokuin were intentionally erased from areas of high visibility. You would not want to show favoritism to any one daimyo, especially a tozama daimyo, by prominently displaying his mark for all to see. For that reason, the best places to see kokuin are actually using a zoom lens to look across the moats. There are also places where the kokuin were hidden by walls and buildings that no longer exist making them more visible today.
At Edo Castle, kokuin tend to be mixed up. There are some areas where you tend to see a lot of the same marks, but rarely do you find a spot that is exclusively one mark. This is something you will see more often at Osaka Castle where the quarrying and building of sections of the stone walls was done by the same daimyo. As mentioned earlier, the walls built under Hidetada as well as repairs and changing of some of the walls at Edo Castle over time led to the kokuin being more generally mixed together. In a few places you can find a section of wall where there is a clear break between one daimyo and another. The left photo below is particularly interesting. Enlarge the photo and you'll see a clear break between the kuyo (nine stars) kokuin on the right and the wachigai (overlapping circles) kokuin on the left. We know that the stone walls behind the honmaru around the Kitahanebashi Gate were some of the earlier walls built at Edo Castle so I would surmise that this spot was both quarried and built by the respective daimyo.
Visiting Stone Quarries 〜石丁場を訪ねる〜
If you've read this far into this kokuin journey, let's go visit some of the former stone quarries in Izu.
Ito City has taken some steps to make a bit of tourism out of the Usami stone quarries. They have developed some hiking trails and maps to get to the sites. There is also a trail around the town where kokuin stones have been intentionally displayed for visitors. There are also several locations up and down the Izu coast where leftover stones have been found or moved to small parks for you to visit too. Several of these are documented below, but it is not an exhaustive list.
Exploring the ruins of former stone quarry sites is actually great fun and the quarries themselves are a much under appreciated part of castle building history. Walking the quarries, you can really imagine them being an active site. Depending on the site, there are stones in all stages of being cut and formed, including mistakes or incorrectly split stones. After visiting a few sites, you can imagine the full range of activities at such stone quarries. You will see stones that were left behind and never carried off to Edo, called zan'nen seki. There are "leavings" (as I call them) which are the leftover bits carved off a stone that have many ya-ana (arrow holes). Most of these sites have no trails or signs so it's up to you to explore. Check each side of a stone and sometimes clean them off to see if there is anything under the fallen leaves or weeds. You could probably spend a full day at any one of these sites. Explore my photos of these quarries below to see what you might find too!
One of the fun aspects is to match kokuin from a quarry with kokuin found at Edo Castle. Many of the photos above showing kokuin at Edo Castle were intentionally selected because they show kokuin that may be found in the albums of the quarries documented here. Two examples are shown below.
Stone Quarry Profiles 〜石丁場の概要〜
Several years ago, I befriended a retired researcher who had a special interest in the stone quarries of Izu and helped to get those around Usami and protected as a National Historic Site in 2016. I joined him on some travels to re-visit some of these sites over the past few years. A very few of these photos from Usami and Heda were posted to Facebook at the time, but most are seeing the light of day for the first time. The photos are also GPS tagged and I'm providing maps of these photos and quarries for reference purposes only. Many of these are on private land and the owners do not appreciate people walking around their woods without permission (risk and liability claims). Please refer to the descriptions of each quarry for more details about access.
The best quarry visited. If you only look at one quarry gallery on this site, see these photos. The site seems to be in the early the process of removing stone so there are a lot of large stones in different stages of being shaped and many kokuin marked stones.
One of the most fascinating and accessible quarry sites. It is right on the coast where they carved out large blocks of stone. You can also find other interesting features only seen here.
The best site for anyone to visit. There are a lot of stones and kokuin along a nice trail that is easily accessible from the station. This is probably the only quarry that has been partially developed for tourism.
A coastal quarry where some of the big boulders were split up for castle stone. A few ya-ana holes and a few kokuin remain, but well scattered. The main site is the huge stone in the photo here.
A few stones left behind from the former quarries that have now been developed over. The most interesting part is the border marker stone for the Mito Tokugawa, click through to read why.
The site was discovered during road construction so a small bridge was built over the site. There is a sign along the roadside and a few large stones are preserved under the bridge.
This site is interesting because it is nearly quarried out. You will see some flat areas and no remaining exposed bedrock nor boulders, just a few broken stones left behind.
A few stones have been placed around town making a walking trail. They are mostly stones that were left behind while being taken to the port or placed here intentionally. The large boulders and stones of the coast were also shaped and taken to the castle.
Author's note: I started writing this article some time (years) ago and have stopped and started several times since. It seems once I get caught up on updating castle visits I come back to this topic but never quite finish it as I inevitably visit more castles that need to be updated. With the long State of Emergency this winter 2021 due to COVID-19 I tried to pull this information together into one cohesive article. It originally started as a project to document all the little places around Tokyo where you can find remains of the original Edo Castle stone walls and other interesting castle wall trivia. That article morphed into a showcase of kokuin, but I can't talk about kokuin without talking about "why" the stones were marked. That leads to tenkabushin and stone quarries and that gave me the perfect showcase to dig out and organize my stone quarry photos. If the article seems a little disjointed, that's why. It followed my own journey down this rabbit hole. Now that I have this "starter" article out of the way, I'll flesh out some of the other topics that have been dropped along the way, but for now, here is the (hopefully) first article in a series about Edo Castle Stone Walls. If anyone wants to sponsor me to write a book about the stone walls of Edo Castle, please reach out and I'll get it done much faster! I think I probably have enough content for a whole book stored in PDFs, photocopies, Evernote and random trivia locked up in my memory.
April 18, 2021