The nature of the first Japanese castles illustrates another factor that arose from Japan’s isolation from continental Asia – the development of a very different tradition of defensive architecture from that of China and Korea. The biggest variation lay in the almost total absence from Japan of the walled town, which was where the wealth of Ancient China was concentrated.
With no barbarian hordes to fear on their islands, the threat to Japan came mainly from internal rebels, who tended to establish themselves in purely military strongpoints. As the Japanese landscape is predominantly wooded and mountainous, it is not surprising to find these two factors combined in the design of most of Japan’s earliest fortresses. A multitude of hilltop sites provided both the defensive topography and the building materials that were needed to strengthen their natural positions. The result was the development of a style of castle known as the yamashiro (mountain castle), which was to continue being built in remote areas long after the introduction of stone castles, due to reasons of convenience and availability.
For the earliest yamashiro (and for simple fortresses right throughout the period) little was done to alter the overall shape of the existing mountain or hill other than stripping the summit of enough tree cover to provide building materials and to allow good fields of view and arcs of fire. The slopes of the steeply sided hill or ridge would be allowed to retain their forested cover to prevent soil erosion and to provide another defensive barrier. Firm footpaths would be constructed linking different peaks together, thus producing a yamashiro complex that consisted simply of a number of stockaded hilltops joined to each other.
There are several illustrations of yamashiro castles in the picture scrolls of campaigns and battles fought during the Later Heian Period, from about AD 950 onwards. In all cases the landscape has been used intelligently and economically. This leads to numerous variations of yamashiro depending on location, with great differences between those located in mountainous areas and those built in flatlands surrounded by rivers and flooded rice fields, where the castle would be referred to as a hirajiro (plain castle). A mixture of the two styles was known as hirayamajiro (a castle on mountain and plain). On the excavated hilltops there would be built quite intricate arrangements of wooden palisades, decorated wooden towers, gateways and domestic buildings. The solid wooden walls of the palisades were pierced with arrow slits, and in some cases rocks were slung by ropes through holes. In the event of an attack the rope would be cut, allowing the rocks to fall against an enemy. Towers were enclosed at the top with wooden walls or portable wooden shields, and from these vantage points archers fired longbows and crossbows, or simply threw down stones, the only other missile weapons available. Domestic buildings thatched with rice straw would also be built from wood, and acted as quarters for the garrison, reception and command areas for the general, as well as stables and stores.
The moat and part of the walls of the mighty Osaka castle, built by Toyotomi Hideyoshi in 1586. This image shows the interesting contrast between the seemingly haphazard arrangement of stones in the main sections of the walls and the neat dovetailing of fully dressed stones where the walls intersect to form exterior corners.
A detail from the picture scroll of the Gosannen War, showing the wooden tower of a yamashiro that has been attacked by arrows. Rocks ready for dropping hang by ropes through holes in the tower.
The main defensive purpose of the yamashiro was to restrict a hostile forces access to an area, and also to keep his forces under surveillance. Communication between the hilltop redoubts was vital so that troops could be moved along the mountain paths from one sector to another as required. Also, if a lower section of the yamashiro complex was lost, then the overall design was supposed to permit the garrison to launch a counterattack with ease, or at the very least isolate the now hostile portion of the castle. With no stout walls like those round Chinese cities to batter down, the Japanese had no need of siege catapults, for which quite a science existed in China. Instead any siege machines used, such as large crossbows, tended to be employed in an anti-personnel role prior to an infantry assault. Thus we read of the use of oyumi (crossbows) in northern Japan that the arrows ‘fell like rain’, killing hundreds of samurai and causing fires, but not that they broke down any walls. This was the style of Japanese castle that played such a vital role in the Gempei Wars of 1180–85.
The above description of a fairly rudimentary wooden fortress on top of a hill continued to apply for many years, and a daimyô’s smaller outposts during the Sengoku Period would have resembled it almost exactly. But as time went by many changes occurred. The first was a more creative use of the natural slopes afforded by the wooded hillsides: the forest cover was stripped away almost entirely and the gaps between adjacent ridges were further excavated to make ditches. In such a way a roughly concentric series of mountain peaks could be converted into a number of natural inner and outer baileys, each overlooking the one below it, utilising not only the tops of the hills but different intermediate levels also. As this technique developed, the tops of successive baileys were levelled or even enhanced to create interlocking fields of fire by shaping the mountainside. The result was a series of sculpted earth bastions reminiscent of the ‘Old Dutch’ developed in the Netherlands at roughly the same time, but with two important differences. Firstly, the Dutch fortifications were built on flat and low-lying surfaces and, secondly, they were created by adding to the landscape rather than removing considerable sections of it. Some ingenious sculpted forms were created in Japan. Ditches were strengthened by having vertical cross pieces built through them at right angles to the inner walls. Near perpendicular sections were made more dramatic by having long channels cut out of them, down which rocks could be rolled. Mountain streams were diverted into gullies to create moats, and entrances to gateways were offset to allow an enemy’s approach to be covered completely.
This exhibit within the Uto tower of Kumamoto castle shows how the plastered walls of a castle keep were constructed on a type of wattle and daub arrangement. Bamboo poles were placed over a stout beam and lashed together both vertically and horizontally. A layer of plaster, which was remarkably fireproof, was applied to the surface, and painted white. A similar, but cruder method was used for the small walls that appear on the tops of the stone bases of a castle.
The interior of a section of small wall at Kakegawa castle. The triangular gun ports and the rectangular arrow ports can be seen, as well as the wooden supports inside the walls, over which planks could be laid to create firing platforms, and the tiles that gave protection from the weather.
Shikizan castle, 1550
This plate shows Shikizan castle, which was owned by Matsunaga Hisahide. He died here following the siege by Oda Nobunaga in 1577, after which the site was abandoned. Shikizan shows the culmination of the sengoku yamashiro style common before the widespread use of stone-clad bases. A roughly concentric series of mountain peaks has been converted into a number of natural inner and outer baileys by carving up the mountain. Each layer overlooks the one below it, utilising not only the tops of the hills but different intermediate levels also to create interlocking fields of fire. The result is a series of sculpted earth bastions. Ditches have been strengthened by having vertical cross pieces built through them at right angles to the inner walls, and near perpendicular sections are made more dramatic by having long channels cut out of them, down which rocks could be rolled. Mountain streams have been diverted into gullies to create moats, and entrances to gateways are offset to allow an enemy’s approach to be covered completely. Walls have been built using a form of wattle and daub construction plastered with a mixture of red clay and crushed rock. Arrow ports were cut at regular intervals. Outbuildings and towers are simple structures.
At the same time more elaborate walls and buildings were raised, and in place of the loose wooden palisades of the old days more substantial surrounding walls were built using a form of wattle and daub construction. Stout vertical wooden posts were driven into the earth at six-foot intervals with bamboo poles placed between them and bundles of bamboo, lashed together with rope, as the core. The resulting structures were plastered with a mixture of red clay and crushed rock, and were often whitewashed, giving a Japanese castle its characteristic appearance. Arrow ports were cut at regular intervals. To keep weather damage to a minimum the walls were topped with sloping thatch, wooden shingles, or even tiles. In many cases the walls were supported on the inside by a series of horizontal and vertical timbers, and at times of attack planks were laid across them to provide platforms from which guns or bows could be fired over the walls. Similar platforms could also be fitted to gates.
The great weakness of the sengoku yamashiro model was the inherent instability of the natural foundations created from a sculpted hillside, particularly where the forest cover had been removed. Three storeys was the absolute maximum that could be risked for an enclosed tower with rooms, and outlook towers tended to be mere skeletal structures. To bind the soil on exposed sections grass was allowed to grow, but the torrential rain of Japan took a heavy toll of foundations and structures alike. Even if there were no typhoons, earthquakes or sieges to create additional havoc, normal wear and tear demanded that the plastered walls be routinely repaired at least every five years. If stronger, and therefore heavier, structures such as keeps and gatehouses were to be added, then something more substantial than a grassy bank was needed as a castle base, and the solution to the problem was to provide the Japanese castle with its most enduring visual features. These were the great stone bases, a fundamental design element that can be identified in even the most ruined castle site. So strong were these creations that the foundation walls of the castle of Naha in Okinawa was able to withstand a bombardment by the US Navy in 1945!
The particular feature to be noticed here in this reconstructed section of the walls of Shoryuji castle is the grassy bank, which in the later forms of castle was replaced by the massive stone bases. This is a simple corner tower with a stone dropping port and very rudimentary stone reinforcements to the wall.
It is the stone base that defines the Japanese castle. This example, from Iga Ueno, shows the dramatic curve of the stone base as it descends into the moat. The keep is just visible above the line of trees that have been planted to shield the interior of the castle from prying eyes.
To a large extent it is these stone bases that are the essence of ‘Japanese castles’ of the Sengoku Period, because many never had elegant tower keeps, such as those at Himeji and Hikone, raised above them, simple wooden buildings and plastered walls were often enough to augment the stone bases. It is also with these stone bases, rather than any superstructure, that comparisons can be made with the European bastions of the trace italienne. However, as has already been stated, the evolution of the Japanese form was very different from that of Europe, especially with regard to construction techniques. A European bastion was built from scratch, either completely from stone or from earth (whether the earth was clad in stone or brick revetments or not), while a Japanese one tended to be carved as in the descriptions above and then clad in stone. The result in either case was the same – an immensely thick defensive wall.
It must not, however, be thought that the new style of stone castle immediately supplanted the earlier models. Apart from financial considerations, there was also the added complication that few daimyô relied on one castle alone, and instead maintained networks of ‘satellite’ castles. The central castle in a daimyô’s territory was called the honjô (main castle), which was supported by a number of shijô (satellite castles). In some cases these shijô would operate independently of the honjô, and in the fief of the Hojo family, for example, they were used for administering occupied territories. Shijô were invariably commanded by members of the daimyô’s own family or his most trusted hereditary retainers. Some shijô would be miniature versions of the honjô, demonstrating a similar use of stone bases and wooden towers, but related to them would be another network of sub-satellite castles, which would probably be old-style sengoku yamashiro with sculpted hillsides and plastered walls, but little else in the way of elaboration. Finally, these sub-satellites would themselves be supported by small stockade fortresses indistinguishable from the time-honoured yamashiro. These little castles were not necessarily permanently garrisoned, but weapons would be stored there and part time soldiers would take control on declaration of an emergency situation. The Hojo’s Gongenyama castle, for example, had a strength of 252 men, so they were more than just lookout posts. As a result of the satellite system, therefore, even as late as the 1590s, it was possible to see examples from all the different periods of Japanese castle development still in use.
The ‘snout’ of the corner of the stone base-cum-wall of Hirado castle is shown here. Note the massive stones, the ne ishi or root stones, at the foot of the wall. The harbour of Hirado can be seen in the distance, and there are the traditional pine trees planted behind the line of the wall.
The striking red bridge of Matsumoto sets off the beauty of the keep that lies behind it. Unlike most castles, which were built on hills, Matsumoto is a hirajiro, ’a castle on the plain’, except that the immediate plain is beside the wide river that forms its moat. The complex we see today consists of the keep (built in 1597) and an attached northern tower that perfectly balances it. Both in its external appearance and its perfectly preserved interior, Matsumoto is the Japanese equivalent of the Taj Mahal.
Kakegawa castle, 1610
A welcome trend has in recent years been the rebuilding of Japanese castle keeps using the correct materials and based on the plans that the daimyô was required by law to keep. This plate is of the outstanding example provided by Kakegawa castle.
Total floor space: 304.96m2
Height above ground: 19.78m
The introduction of stone as a building material not only combated the problem of soil erosion and weather damage, it also allowed castle designers to raise new structures that would previously have been thought impossible, leading to the Japanese castle as we know it today. Stone castle bases sloped dramatically outwards, as did European artillery bastions, but the geometrical reasoning behind them was very different. The horizontal geometry of a European bastion was primarily concerned with discovering the ideal angle for providing covering fire with no blind spots, and its vertical geometry was designed to keep to a minimum the amount of soil that would spill out after bombardment (thus affording a ramp to the enemy), and to provide a sufficient angle to make scaling ladders impossibly long. The Japanese considerations were more ones of strength, both to hold back the inner core (which in the case of a stone castle on a flat surface, such as much of Osaka castle, had to be artificially created) and to take the weight of a keep. There was also the constant threat of earthquakes, which occur frequently in Japan, and it was found that long and gently sloping stone walls absorbed earthquake shocks very well.
The keep of Hikone castle, first erected at Otsu in 1575, is one of the finest of the original keeps left in Japan. It has a characteristic stone base, and the windows of its upper storey are finished in kato mado style with an external balcony. It was the seat of the Ii family.
The foremost exponents of stone base construction were the masons of Anou in Omi Province. They had specialised for centuries in the building of stone bases for temple buildings and pagodas, and their clever use of trigonometry revolutionised Japanese castle design. Through the use of massive shaped stones the base could not only be sloped, but could also be given a curve. This ensured that the stresses could be directed very accurately to give the solid foundation that was sought. The Anou masons appear to have come on to the scene in 1577, by which time several tower keeps had already been experimented with. The daimyô Matsunaga Hisahide is credited with the first tower keep at his castle of Tamon in 1567, but nothing of it has survived. Maruoka’s keep was built in 1576 and survived almost intact until 1948 when it was levelled by an earthquake, but has since been reconstructed using the original materials. The oldest original keep is probably the beautiful Matsumoto, which can be reliably dated to 1597. Older keeps exist, but they have all been relocated to their present sites. Hikone’s keep, for example, started life as Otsu castle in 1575 and was moved to its present location in 1606. Of castles in existence in situ prior to the siege of Osaka in 1615, Inuyama, which looks down dramatically on the Kiso River, dates from 1600, Matsue, on the coast of the Sea of Japan, from 1611, and the peerless Himeji was built between 1601 and 1610.
All these examples, therefore, date from a time when wars were still continuing, so the popular view that consigns Japan’s extant castles to a time when wars had ceased is far from the truth. Quite elaborate structures existed during the age of samurai warfare, and this can be confirmed by pictorial sources, in particular the painted screens produced to commemorate famous battles in which their patrons took place. One important source is the Nagashino screen in the Tokugawa Art Museum in Nagoya. This shows the famous charge by Takeda Katsuyori (see Osprey’s Campaign 69: Nagashino 1575 by the same author), and in the right-hand corner there is a representation of a castle. The actual castle of Nagashino was probably a simpler structure than the stylised one shown here, as it was a frontier emplacement out in the country, but the castle on the screen may be justifiably regarded as a good example of the developed form that would be used as a daimyô’s honjô. One other very important source is the screen of the Summer Campaign of Osaka, 1615. Here the representation of the keep tallies very well with what is known of its contemporary appearance.
Far from being a product of the peaceful Edo Period, therefore, the elaborate tower keep, designed as much to impress an enemy by a display of the daimyô’s wealth as for military considerations, was an integral part of Japanese castle design almost as soon as the techniques were developed to allow it to be built. In fact one of the most spectacular keeps of all was one of the earliest. This was Oda Nobunaga’s glorious castle of Azuchi, burned by rebels at the time of Nobunaga’s murder in 1582. Nothing remains of Azuchi above its stone base, but enough illustrations and descriptions of it have survived to allow its appearance to be reconstructed with some confidence. One feature of Azuchi, never repeated anywhere else, was the building of an octagonal tower as the uppermost of its seven storeys.
In 1586 Toyotomi Hideyoshi, who succeeded Nobunaga, commissioned Osaka castle, which was to add its own chapter to the history of Japanese castle building. It was built on the ‘great slope’ (o-saka) that had formerly housed the fortified cathedral of Ishiyama Honganji, the headquarters of the fanatical Ikko-ikki sect who had defied Oda Nobunaga for ten years in Japan’s longest ever siege. The solid base, although of modest height, lay in the midst of a bewildering maze of rivers, reed beds and ever-changing islands that made up the estuary of the Kiso River where it entered Osaka Bay. This topography, the classic hirajiro situation, was cleverly exploited in the construction of Osaka. Concentric rings of huge stone walls built around earth cores provided multiple layers of defence with little height advantage until one moved closer to the central keep, which was of such a size as to dominate its surroundings completely.
Inuyama castle holds a dramatic and romantic position above the Kiso River. It is still owned by the same family who built it in the 17th century.
As noted above, it is the existence of the huge stone bases, rather than any particular superstructure on top of them, that essentially defines the Japanese castle. However, the passage of time has made it increasingly difficult to study them properly. This is sometimes because of neglect of the site or alternative use of the land (which is often prime city-centre real estate), and in some cases the site has been harmed by the rebuilding of the original castle tower in concrete. This has happened, with less than perfect results, at Nagoya and Osaka, and some reconstructions elsewhere have not even been built in the original place.
Curiously, one of the best places to see Japanese castles in their original state is not Japan at all but South Korea. When Japan’s invasion of Korea in 1592 faltered in the face of Chinese and Korean counterattacks, the Japanese forces raised a series of coastal forts called wajô (the castles of Wa, i.e. Japan) to protect their communications. As the native Korean castles had fallen so easily to their blitzkrieg advance the Japanese turned to their own tried and tested method of carving up a hillside and cladding it with stone to produce a fortress. The immense amount of labour required to produce such structures in a short time was provided by press-ganged Koreans or Japanese peasants shipped across the sea. As there was no time to raise huge tower keeps on these structures (and Ulsan castle was besieged even before it was finished) only the simplest of towers were added, although a European visitor remarked on how lavish the interior decoration of the domestic buildings could be. The wajô had a very short lifespan, four years at the most, and were abandoned to the elements when the Japanese finally departed in 1598 and they remain in the same state to this day.
The defence of the earthwork Sanada barbican at Osaka, 1614
Primitive-looking earthworks and wooden palisades formed the main element of the barbican built out to the south of Osaka castle to strengthen its defences prior to the great siege of 1614/15. It was named the Sanada-maru after the castle commander, Sanada Yukimura, and saw much action in the winter of 1614. On top of the earth bastion a simple but effective two-storey wooden wall with firing platforms was constructed. The earth absorbed the Tokugawa cannon balls.
There is a considerable body of evidence to suggest that walls of earth formed part of some Japanese castle designs. As in the European context, earth bastions had the advantage of speed and economy, although they were always a temporary solution. The most important example of the use of earth ramparts by the Japanese occurred in Korea in 1593. Being faced with the rapid advance of a Chinese army with a formidable artillery capability against P’yongyang, the Japanese army abandoned the native Korean stone walls of the city and took to the spade to throw up earthworks outside the walls. The Ming commanders, proud of their Great Wall of China, scorned these ‘burrows’ as the creations of barbarians until they felt the arquebus balls discharged from behind them, and in any case when winter came the earth ramparts froze as solid as stone.
Earthworks also formed the main element of the barbican built out to the south of Osaka castle to strengthen its defences prior to the great siege of 1614/15. It was named the Sanada-maru after the castle commander, Sanada Yukimura, and saw much action in the winter of 1614. On top of the earth bastion a simple but effective two-storey wooden wall with firing platforms was constructed.
When Japan’s invasion of Korea in 1592 faltered in the face of Chinese and Korean counterattacks, the Japanese forces raised a series of coastal forts called wajô to protect their communications. This is one of the best preserved examples, the wajô of Sosaengp’o.
The Sanada-maru was essentially a temporary structure to meet the demands of the moment, and was not copied elsewhere. Instead the final flourish in Japanese castle design went to the other extreme, and by the time of the fall of Osaka in 1615 the keeps that now grace the Japanese landscape had all been completed. Like so many other things in Japanese military history, with the establishment of the Pax Tokugawa developments in castle architecture came to an end. The castles might be rebuilt after fires or earthquakes, but until the coming of Europeans in the 19th century forced a reaction, the Japanese castle remained as the most visible and attractive symbol of past military glory.
