Looking across the Hikiji River at the hill that was once the site of Oba Castle.
A samurai lord sits on a hillside, still dressed in his armor, looking across the swamp that stretches before him. Ise Sozui, known to history as the great Hojo Soun and founder of the mighty Late Hojo Clan, looks out across the wetlands at the small castle that has held his forces at bay. For days, this small, forgotten Usesugi outpost had stopped the powerful Hojo army from marching on to Edo. Yet, Oba Castle hadn’t always been the unimportant border fort that Hojo Soun had expected to steamroll on his way to bigger and better things. Centuries prior, it had been the seat of power for a great clan and the administrative center for one of the most important districts in Sagami Province at a time when Sagami Province was one of the most important in all of Japan. This is the story of Oba.
The current main hall of Oba Shrine.
People have lived in and around modern day Fujisawa for longer than history records. Archeologists have found the remains of shell mounds and villages dating back thousands of years. But our story starts in 927, when a local village built a shrine on a hillside southwest of Kamakura which they called Oba Shrine. A small village grew up around the shrine and in 1104, a warrior and hero of the recent Three Years’ War, Kamakura Kagemasu, recruited a group of vagabond samurai to establish the Oba Mikuriya, or Oba Agricultural District, with Oba village at its center. Created as a temporary, though often repeated, donation to the great Ise Shrine, this Oba district and its 12 villages became one of the largest and most important suppliers of food and goods to the imperial court in Kyoto. This was not a peaceful time in Japan though, and the Three Years’ War was far from the only conflict Japan would see in the late Heian period. After all, this was the time of the rebellions that would lead to the Genpei War, and the Oba would be party to many of the major events of the time. And even under the protection of Ise Shrine and the Emperor, the Oba Mikuriya wasn’t safe. In 1144, after the Minamoto Clan took control of Kamakura, Minamoto no Yoshitomo declared that the Oba district should be part of his estates. To support his claims, he began raiding the land and attacking villages. As a result, Oba Kagemune,Kamakura Kagemasu’s nephew (or maybe his cousin. Or is son? Or his adopted heir? No one really knows.), built the fortifications of Oba Castle to defend the Oba lands while they appealed to the Emperor and Ise Shrine for help. And while an edict from the Emperor in 1145 stopped the raiding, at some point, the Oba Clan would shift their allegiances to Minamoto no Yoshitomo.
Cherry blossoms around one of the baileys of Oba Castle
This brings us to the most influential and famous of the Oba samurai, the brothers Oba Kageyori and Oba Kagechika. In 1156, the brothers were called to aid Yoshitomo in putting down the Hogen Rebellion, where Kageyori was forced into semi-retirement after taking an arrow to the knee. No joke, Yoshitomo’s half-brother, Minamoto no Tametomo shot him in the knee with an arrow, which shattered his kneecap and left him with a bad limp for the rest of his days. This left his younger brother Kagechika as the defacto head of the clan while Kageyori retreated to modern Ibaraki prefecture to recuperate. Kagechika went on to serve Yoshitomo throughout the 1150s until the near complete destruction of the Minamoto Clan in the Heiji Rebellion of 1159, after which, he went home to Oba Castle.
The grave of Minamoto no Yoritomo
Following the Heiji Rebellion, rather than punish the clans that had backed the Minamoto uprising, the new Taira dominated government went on a huge public relations push, actively recruiting their former enemies to their cause. This created a rift in the Oba Clan, as Kageyori, still disabled from his arrow to the knee, remained loyal to the shattered Minamoto while Kagechika, as head of the clan, took the Taira up on their offer and became one of the most influential samurai lords in Sagami and the commander of a Taira army. This wouldn’t last, however. In 1180, one of the three surviving sons of Yoshitomo, Minamoto no Yoritomo, managed to escape his exile with the help of his Taira father in law, Hojo Tokimasa, and on the orders of Prince Mochihito. Kagechika responded to this news by raising his Taira army to put Yoritomo back into his box. After all, the Oba now had a really good thing going, and Kagechika didn’t need another Minamoto/Taira war to ruin that. At Mt. Ishibashi, in the south of modern day Odawara, Kagechika ambushed a greatly outnumbered Yoritomo and his handful of warriors in the night during a fierce thunderstorm. According to legend, Yoritomo was forced to hide in a hollow tree trunk while his supporters fought and led Kagechika’s forces away before he could finally escape into the night. Yoritomo eventually made it down from the mountain to Sagami Bay, where a boat took him to his Miura Clan allies and from there to Musashi province where he raised a huge army. The Genpei War was back on, not that Kagechika would survive very long. Two months after crushing Yoritomo at Mt. Ishibashi, Oba Kagechika was rushing to link up with main Taira forces coming up from Kyoto when he was cut off and surrounded by Yoritomo’s much larger force. Seeing no other option, he disbanded his army and fled, hoping that the main Taira army would relieve him and allow him to break out. When that Taira force was soundly defeated at the Battle of Fuji River, Kagechika knew he was out of options. He surrendered to Yoritomo, and after his brother Kageyori declined to beg for his life, he was executed on the banks of the Katase River, not far from where I currently sit and write this article.
Stones that mark the foundation post holes of one of the buildings within Oba Castle
Of course, Kageyori had not been idle in all of this. He was one of the many samurai to flock to the Minamoto banner once it had been raised again, serving as one of Yoritomo’s advisors. When Yoritomo re-established his residence in Kamakura, it was Kageyori who was tasked with building his new palace. He also had a hand in creating the pond at the famous Tsurugaoka Hachiman Shrine in the center of Kamakura. Under Kageyori’s renewed leadership, the Oba Clan saw continued success in the new Kamakura Period as retainers to the new Shogun, Minamoto no Yoritomo. Sadly, this would be the high water mark of the Oba Clan and of Oba Castle. For, soon after Yoritomo established his new Shogunate in 1189, Kageyori finally retired fully, becoming a monk and naming his son, Oba Kagekane to succeed him. He would be the last of the Oba samurai to live in Oba Castle.
Under the new Shogunate, Minamoto no Yoritomo’s father-in-law, the head of the Hojo Clan exercised great influence over the new government and court. And over time, the influence and control of the Hojo clan only grew, with Hojo Tokimasa eventually serving as the first regent to the Kamakura Shoguns after plotting and deposing Yoritomo’s eldest son in favor of his 12 year old youngest son. This did not sit well with many of the other influential clans, and thus 1215, a plot was hatched to overthrow the head of the Hojo Clan and limit their power. Whether Oba Kagekane was part of this conspiracy or how much of a part he may have played is unknown. What is known is that, when the plot failed and the resulting Wada Rebellion was immediately crushed, his name was put forward as one of the primary instigators. Facing certain death at the hands of the now all-powerful Hojo, the Oba Clan did the only thing they could. They fled the resulting purge and scattered, with Oba samurai later turning up in Chikugo (modern day Fukuoka) and Bingo (Hiroshima) provinces in the following years. The clan would persist in some form for centuries after, but it is believed that at some point during the Sengoku Period, they were either absorbed into another clan or died out completely.
The entrance to Oba Castle Park, Obajoshi Koen. The small welcome center had an exhibition about the details of the castle’s history which was very helpful for writing this article.
Following the fall of the Oba Clan, the Oba Mikuriya and Oba Castle passed to the Miura Clan for a time before they too fell from grace. Ultimately, by the end of the Kamakura period, the Hojo Clan controlled the area directly, making it the most influential district in Sagami Province. The castle, meanwhile, remained a modest fortification which was entirely bypassed when the Ashikaga Clan attacked Kamakura in 1333 during the revolt of Emperor Go-Daigo and the ultimate fall of the Kamakura Shogunate. Under the Ashikaga Shogunate and into the Sengoku Period, the castle passed to a branch of the Usesugi Clan, during which time, the great castle builder Ota Dokan – who built the original Edo Castle – took possession of Oba Castle and thoroughly updated and remodeled the fortifications. When Dokan died, however, a power vacuum was formed in the Kanto plain and a young upstart son of a retainer within the Imagawa Clan decided to strike out on his own and stir up some trouble. His name was Ise Sozui, but history will remember him by the posthumous name his son gave him, Hojo Soun, founder of the Later or Go- Hojo Clan, Lord of Odawara, and one of the great samurai commanders of the Sengoku.
A topographical map of the area around Oba Castle (the hill in the center of the frame) from the 1970s. The blue area is low land mostly used for rice farming. It is easy to see how a dike or damn to the south (left) of the castle would turn this low land to swamp.
Hojo Soun set out from Imagawa lands and quickly carved out a place for himself, winning battle after battle, taking the Odawara Castle and expanding it into his primary stronghold. In or around 1512, however Soun decided to march his armies north to take Edo and Kawagoe Castles and cement his control over the Kanto Plain. To reach Edo, however, he would have to march through Oba and thus, he laid siege to Oba Castle. Soun had an overwhelming force at his back when he arrived in Oba, but Dokan’s upgrades to the castle were effective. According to the legend of the Funejizo (a small shrine located near the castle dedicated to the battle), the castle was surrounded by swamp and wetlands from where the nearby Hikiji River meets another, smaller river that flows from the opposite side of the castle. As a result, the Soun’s forces could only attack the castle from a narrow land bridge which negated their advantage in numbers. After several days of failed attacks, it is said; Soun was standing on a hillside, looking over the swamps and fuming in rage when an old woman approached selling small meat buns. She saw Soun’s frustration and asked the mighty Daimyo what was troubling him. Hearing his situation, the old woman remarked that there was a dike a short distance down river which held the water back. If Soun could breach that dike, the water in the swamp would drain away and he would be able to attack the castle from all sides across dry land. Suon, seeing that the old woman spoke the truth thanked her for her help, and then promptly killed her to make sure she could not alert his enemies that he had learned their secrets. He had the swamp drained and quickly took the castle. The old woman is memorialized by the nearby Funejizo monument I mentioned before.
The Funejizo (boat statue) that sits in memorial to the old woman who told Hojo Soun how to defeat the castle.
Initially, the Go-Hojo takeover of Oba Castle meant upgrades and further expansion of the castle, but that didn’t last long. Once Tamanawa Castle was completed nearby and other, more formidable defenses were constructed along the Go-Hojo’s ever expanding borders, Oba Castle became ever more irrelevant. Archeology shows that by the Siege of Odawara in 1590 and the Tokugawa takeover of the entire region, many of the moats had been filled in and the site gradually converted to more of an administrative center than a fortified position. Once Tokugawa Ieyasu took over and established his residence in Edo, Oba Castle was abandoned completely. By the 1970s, when Fujisawa city established a park on the site, the hilltop that had been the central baileys of the castle was tilled farmland, and only a few moats and ditches remained. Archeology also found the remains of the foundation posts of one of the buildings. Today, that is all that remains of what, at one time, was the seat of a great and proud samurai clan.
This small tori gate leading to Oba Castle supposedly collapsed in the 1923 Great Kanto Earthquake and was never repaired.
What of the Oba Mikuriya then? After the Kamakura Period it falls out of the records that I could find. Eventually, it was broken up with each village becoming independent within Sagami Province until the Meiji Restoration and the late 1800s, when many of the smaller villages were merged together under the administration of the newly created Kanagawa Prefecture. Today, those lands now make up the cities of Fujisawa and Chigasaki, as well as parts of the surrounding cities, like Yamato, Yokohama, and Kamakura. Oba village is now just a district within the northern part of Fujisawa, a half hour walk from Zengyo Station and most easily reached by bus. Oba Shrine still exists, with an additional dedication to Oba Kagechika. But it went from one of the important Sagami Shrines to a largely forgotten satellite shrine administered by Tsurugaoka Hachiman Shrine in Kamakura. One of the small Torii Gates that lead to the main shrine building was toppled in the Great Kanto Earthquake in 1923 and still lays in pieces beside the path, with no one willing to put the time or effort into repairing it.
And so ends the story of Oba, once it was the seat of a great samurai clan and the center of one of the largest districts that supported and fed the Imperial Court. Yet, today, it is just a footnote in history, largely forgotten even by the people who live there. But I still remember, and I hope you will remember too.
If you want to visit, I suggest visiting during the first week of April when the cherry blossoms are in full bloom as the main bailey of the castle is full of cherry trees. It can be accessed to the west of Zengyo Station on the Odakyu Line along with the Hikiji River Park and Oba Shrine.
Sources:
The History of Kanagawa by the Kanagawa Prefectural Government – https://archives.pref.kanagawa.jp/www/contents/1643172091517/
Displays found at the Oba Castle Welcome Center
Japanese Wikipedia and other Japanese language history sites.