last revised: January 10, 2005

A Brief History of the Castles of the
Oishi Clan in Western Tokyo

Home | Index by Charles T. Keally

photos are after text

Castle building in Japan began at the dawn of Japanese history, but the most active time for castle building was the Medieval Period (1185-1568), especially the later half, also called the Sengoku Jidai, or Warring Nation Period (1482-1558). Few of these castles still have buildings, and most of the present buildings were constructed after the Medieval Period, many in recent times. Most ancient castles are seen today as unnatural terraces on hills or mountainsides, brush-filled ditches where the dry moats were, and eroded earthen walls or embankments. A brief look at the history of the castles of one minor clan in western Tokyo will give some idea of what was happening in other regions of the country and among the much more powerful daimyo, or lords of fiefs.

Oishi Nobushige(note 1) moved his main residence from the central mountains to western Tokyo in 1356, in order to be closer to his 13 fiefs in Tama-gun and Iruma-gun in Musashi-no-kuni.(note 2) This residence is known today as Ninomiya-jo, or Ninomiya castle. Its location once was thought to be at the Ninomiya Shrine in Akiruno City in western Tokyo. But excavations at the shrine have found no trace of any castle or even manor house. Most likely this "castle" was a simply fortified manor on a lower terrace a bit to the southeast of the shrine and near the confluence of the Aki and Tama rivers.(note 3) The Ninomiya Shrine itself dates from the Nara Period.

But conditions in the country were unstable at this time, as the Kamakura Shogunate was being destroyed and the new Ashikaga Shogunate was not fully in power. For increased safety, in 1384, Oishi moved to a true castle in the low mountains along the Jimba Kaido highway in the Ange district in western Hachioji City. This castle is called Matsutake-jo,(photos) or Senteyama-jo.(note 4) Matsutake-jo probably already existed when Oishi moved there; its original construction date is not known. This castle was constructed by cutting platforms or terraces into the mountainside, and by digging some dry moats where useful. This terracing can still be seen today. (enlarged map of Matsutake-jo)

Even at this time, the Jimba Kaido was a major route connecting the Kofu basin to the west with the Kanto Plain (Tokyo area) to the east. However, defending this highway probably was not an important matter at this early date. But two centuries later Matsutake-jo likely was important to the defense of the plain from forces invading from the west, although history gives us little to confirm this idea.

In 1458, the Oishi clan moved their main residence to Takatsuki-jo,(photos) a hilltop castle just across the Aki River from the probable location of Ninomiya-jo. The hill is about 40 m high. The west side is a sheer cliff dropping to rice paddies along the Aki River. The north side is a steep slope coming up from the Tama River. This slope is terraced for defense and is the path to the top of the hill today, and probably also was the path when the castle was in use. About two-thirds of the way up is a small spring that would have provided water even when the castle was under attack. The east side drops steeply into a ravine that opens onto the Tama River floodplain. The south side is a narrow ridge leading deeper into the hills; it was cut off by a deep dry moat that can still be seen today. The main castle buildings were on the relatively flat top of the hill, the Hon-maru, or Main Enclosure. Apparently the top of the hill was naturally quite level, because the Early Jomon site there does not seem to have been damaged much by the the castle construction. Medieval ceramic shards can be found today in the agricultural fields on the Hon-maru.note 5

Sixty-three years later in 1521, Oishi Sadashige moved the main residence to Takiyama-jo,(photos) about 1.5 km further east on the ridge of the hills along the southern side of the Tama River. This castle was much bigger than Takatsuki-jo, and about 70 m above the river floodplain. The Hon-maru enclosure was on the highest point of the ridge. Across a deep dry moat was the Naka-no-maru, or Middle Enclosure. There also was a Ni-no-maru (Second Enclosure), San-no-maru (Third Enclosure), and several other named enclosures with residences of various retainers. The north side of the castle was a nearly vertical cliff dropping to the Tama River floodplain. The east and west sides extended along the ridge and were defended by dry moats. The south side was a gentle slope and shallow ravines. The slope was cut to make a number of defense platforms or terraces.note 6 (enlarged map of Takiyama-jo)

The final Oishi lord of Takiyama-jo, Sadahisa, had three daughters and no sons, in a strictly patrilineal society. So his oldest daughter married Hojo Ujiteru, the second son of the lord of Odawara-jo in Kanagawa Prefecture near Mt. Fuji. Oishi Sadahisa then adopted Ujiteru as his own son in 1558. At this time, the Odawara Hojo had effective control over most of Musashi-no-kuni, and the Oishi clan was under them. This marriage sealed the loyalty. Ujiteru made considerable renovations to Takiyama-jo.

Takeda Shingen's forces attacked Takiyama-jo in 1569. Takeda was the major power in Kai-no-kuni, centered in the Kofu Basin in the mountains west of Tokyo in today's Yamanashi Prefecture. Takeda (generally called by his personal name Shingen) was one of several very powerful daimyo vying for control of Japan near the end of the Sengoku Period. When he attacked Takiyama-jo, he camped his 20,000 troops around the hamlet of Haijima in today's Akishima City, across the Tama River from the castle. That put his forces on the best-defended side of the castle, the side with the river and a sheer cliff for defense. Nevertheless, Shingen's forces advanced nearly to the Hon-maru. But Takiyama-jo did not fall. As a result of this attack, and the growing strength and threat of Takeda Shingen, Ujiteru decided to move his main residence to a more defendable castle.

In 1572, Ujiteru began construction of the mountaintop castle known as Hachioji-jo,(photos) and moved there in 1584-1587. The Hon-maru of Hachioji-jo is a small space on the peak of the mountain, over 200 m up the steep sides from the valley below. There are terraces and pathways cut into the sides of of the mountain over an extensive area. Unlike any of the other castles or fortifications in this part of Musashi-no-kuni, Hachioji-jo had numerous stone retaining walls, some of which are still visible -- to those hikers with some mountaingoat genes. Quite near the top of the mountain is a good spring, and there were, and still are, wells in the upper enclosures of the castle. It was a good location for defense and for enduring a seige. But, when Toyotomi Hideyoshi's forces attacked Hachioji-jo in 1590, the castle fell in half a day, with great loss of life.note 7 (enlarged map of Hachioji-jo)

Hideyoshi's forces took some of the captives from Hachioji-jo to their seige forces around Odawara-jo.(note 8) When the defenders at Odawara-jo saw these captives, they know that Hachioji-jo had fallen and decided to surrender with no further fighting. This effectively marks the end of the Sengoku Period and the reunification of the nation, under Toyotomi Hideyoshi.(note 9)

  1. Names of persons are given with family name first, in the native Japanese order. Gun (-gun) means county, or a major section of the ancient provinces of Japan. Musashi-no-kuni, Musashi Province, covered much of the western parts of today's Kanagawa, Tokyo and Saitama prefectures. The name remained in use from the Ancient Period until the Meiji Restoration; the major plain of Tokyo and southern Saitama prefectures is called the Musashino Upland today.

  2. The Oishi clan came to Tama and Iruma from Shinano-no-ku, Shinano Province, present-day Nagano Prefecture, where they probably lived in the hamlet of Oishi-go.

  3. The remains of some buildings dating to the time of Ninomiya-jo were found during an excavation on this lower terrace. But no evidence of significant fortification was reported. The site is completely covered with houses today.

  4. An historical marker at the site says this castle was called Jofukuji-jo, or Ange-jo, Senteyama-jo or Nii-jo.(enlarged map of Jofukuji-jo)

  5. Takatsuki-jo was excavated once a long time ago, but I have never seen the excavation report.

  6. Takiyama-jo is part of a city park and has lots of visitors every year. The park is a very good area for hiking. The city -- Hachioji -- has conducted some excavations at the site, and it is generally well maintained. No buildings have been reconstructed, but some bridges have been built across dry moats where they probably existed in Medieval times. Large panels with maps and numerous identification markers make a visit to this site rather informative.(enlarged map of Takiyama-jo)

  7. Hachioji-jo is a Designated National Historic Site. Nevertheless, the government is now digging an expressway tunnel straight through the heart of the castle mountain. Hachioji City has excavated parts of the site and reconstructed the bridge, stairway and gate for a residential enclosure at the foot of the mountain. Vistors to this site are numerous, especially on weekends.

  8. The Odawara Castle has been rebuilt and can be visited today, not far from the Odawara train station, about 80 km southwest of Tokyo.

  9. This is the view from Hachioji. There was, however, at least one major holdout yet to be defeated, the Nambu clan at Kunohe-jo, or Fukuoka-jo, in today's Ninohe City in northern Iwate Prefecture far to the north of Hachioji-jo and Odawara-jo. This castle was built by the Abe clan in 1569. It then was taken over by the Nambu clan. The Nambu were among the few daimyo in northern Japan who did not align with Hideyoshi, but instead continued to resist. Hideyoshi's forces defeated them in 1591. In the view of Ninohe, this is the real end of the Sengoku Period.

    Kunohe-jo is a flatland castle built on a terrace above a river, unlike the other castles discussed here which were built on the tops of hills or mountains. Kunohe-jo's overall plan is a large square. The various parts are smaller square and rectanglar enclosures, defined by earthen walls and dry moats. Because the other castles are on hills or mountains, their forms are dominated by curved lines. As an accident of my own history, the first castle in Japan that I learned anything about was Kunohe-jo. That happened as a result of a motorcycle trip to the narrow gravel roads of the far north in 1962. In 1967, when I was looking for a topic for my graduation thesis, I came across a newspaper aritlce about castles near my home in western Tokyo. These were the ones discussed above and the next castles that I learned anything about. But, while pondering the location of Ninomiya-jo, I stumbled into an archaeologcial excavation at the Ninomiya Shrine. They were digging the large Jomon site there. Thus, after nearly completing the research for a thesis on the Medieval castles of western Tokyo, I changed the topic to the "Jomon Site at Ninomiya" and became an archaeologist instead of an historian.

1 Distant view of the mountaintop Matustake Castle from beside the Jofukuji temple in Ange, Hachioji City. (enlarged photo)
1 Distant view of the hilltop Takatsuki Castle from near the Ninomiya "castle".
2 The Hon-maru (Main Enclosure) of the Takatsuki Castle today.
3 A small terrace (defense enclosure) just below the Hon-maru.
4 Part of the winding path up to the Hon-maru.
5 View to the west from just below the Hon-maru.
6 The small spring about midway up the path to the Hon-maru.
1 Distant view of the Takiyama Castle from the Tama River floodplain on the north side.
2 The highest part of the Hon-maru, with a modern torii gate and shrine.
3 View from the Hon-maru looking north across the Tama River.
4 The well and earthen walls, or embankments, on the Hon-maru.
5 The reconstructed bridge across the dry moat between the Hon-maru (right) to the Naka-no-maru (Middle Enclosure, left). (enlarged photo)
6 The reconstructed bridge across the dry moat looking toward the Naka-no-maru.
7 A dry moat between the Naka-no-maru and some of the enclosure for retainers' residences.
1 Distant view of the late Medieval mountaintop Hachioji-jo castle in western Tokyo.
2 The reconstructed Hikibashi bridge across a creek to the main residence at the bottom of the mountain.
3 The narrow, crooked entrance at the residence end of the bridge. It is constructed this way for defense. This entrance area has been partially reconstructed after excavation.
4 The stairway leading to the residence from the crooked entranceway. These steps have been partially reconstructed after excavation.
5 The gate to the main residence area viewed from the terrace where the buildings were located.
6 A section of the original stone walling on the late Medieval mountaintop Hachioji-jo castle in western Tokyo. The stones for the wall were gathered from the talus on the side of the mountain where the wall was constructed. (enlarged photo)
7 A section of the original stone walling on the late Medieval mountaintop Hachioji-jo castle in western Tokyo. (enlarged photo)
8 A section of natural stone wall, which is a common feature on the steep side of the castle mountain. (enlarged photo)
9 The Hon-maru at the peak of the mountain. The total area is only about the size of the ground floor of a standard Japanese house today. (enlarged photo)
10 The shrine and related buildings on the wide terraces just below the Hon-maru.
11 Sacred Mount Takao seen from the terrace just below the Hon-maru. Mount Takao is one of Japan's oldest sacred mountains, pre-dating the construction of Hachioji Castle.
12 The view east across the Kanto Plain to and beyond downtown Tokyo, taken from the path just beyond the terraces below the Hon-maru. (enlarged photo)
13 A map of the terracing on the Hachioji Castle mountain. (enlarged photo)