Yamanaka Castle, established by Hojo Ujiyasu in the 1560s, is located in what is now eastern Mishima, Shizuoka Prefecture. This castle served as the first line of western defense for the main Hojo Castle at Odawara. Carved into the side of a 586-meter-high mountain, Yamanaka Castle was strategically positioned along the Tokaido Highway, offering superb views of nearby Mt. Fuji, the ocean, and the road leading to Odawara.
The castle featured five baileys: the Honmaru, Ni-no-Maru, Kita-no-Maru, Nishi-no-Maru, and the Daisaki-de-Maru. These compounds were fortified with well-defended gates, log palisades, and wooden walls equipped with gun and arrow slits. Intricately designed dry moats and steep slopes further protected the castle. Notably, Yamanaka Castle’s unique Shoji-bori and Une-bori moats, which are waffle-shaped with narrow ridges surrounding square depressions, can still be seen and appreciated today. These dry moats were necessary as sourcing and maintaining water at the top of the mountain was impractical.
In 1587, as Toyotomi Hideyoshi neared the complete unification of Japan, he set his sights on the Hojo clan, who had not yet submitted to his rule. As he raised large armies against them, the Hojo fortified their smaller outlying castles, including Yamanaka, which was commanded by Hojo Ujikatsu and supported by around 4,000 samurai. However, these fortifications were incomplete when Hideyoshi made his move in 1590. The Toyotomi army, numbering around 67,000, vastly outnumbered the Hojo defenders at a ratio of 16 to 1. Despite this, the Hojo troops fought valiantly, inflicting heavy losses on the Toyotomi forces. The battle, which lasted barely half a day, or according to some accounts, as little as two hours, ended in the deaths of most defenders and the destruction of the castle. Hojo Ujikatsu and his top generals fled to assist in the defense of Odawara Castle. This battle marked the first skirmish in the Siege of Odawara, leading to the downfall of the Hojo clan.
Declared a National Historic Site in 1934, Yamanaka Castle had reverted to forest, prompting preservation projects to restore its remains. Although no structures remain, the distinctive Shoji-bori and Une-bori moat systems are still visible and appreciated. These moats, with their narrow ridges, ensured attackers could only cross in single file, making them easy targets for defenders. The ridges likely featured wooden spikes and tied ropes to further hinder attackers. In 2006, Yamanaka Castle was listed among the Top 100 Castles of Japan.
See also
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Kubota Castle
The founder of the castle is considered to be Satake Yoshinobu (1570–1633). Yoshinobu was one of the six great generals of Toyotomi Hideyoshi. During the Odawara Campaign of 1590, he took part in the siege of Oshi Castle under the command of Ishida Mitsunari, with whom Yoshinobu developed a good relationship.
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Kavanhoe Castle
Kawanoe Castle is located on the small Wasi-yama hill near the port area of the Kawanoe district in the city of Shikokuchuo, occupying a central position along the northern coast of Shikoku Island. Kawanoe was also known as Butsuden Castle. The term “butsuden” in Japan refers to temple halls, and for this reason it is believed that a Buddhist temple once stood on the site before the castle was built. Due to its location at the junction of four provinces on Shikoku Island, Kawanoe held significant strategic importance and was repeatedly targeted by rival forces seeking military control over the region.
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Yokote Castle
The founder of the castle is considered to be the Onodera clan. The Onodera were originally a minor clan from Shimotsuke Province and served Minamoto no Yoritomo (1147–1199), the founder of the first shogunate. The Onodera distinguished themselves in battle against the Fujiwara clan of the Ōshū branch and were rewarded with lands around Yokote. Around the 14th century, the Onodera moved to Yokote as their permanent residence. Their original stronghold was Numadate Castle, but after a series of clashes with the powerful Nambu clan, they relocated their base to the site of present-day Yokote Castle. It was likely during this time that the first fortifications appeared at the castle.
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Wakayama Castle
Wakayama Castle was built in 1585, when Toyotomi Hideyoshi ordered his uterine brother, Hashiba (Toyotomi) Hidenaga, to construct a castle on the site of the recently captured Ota Castle. The purpose of this construction was to secure control over the likewise newly conquered Province of Kii. Following an already established tradition, Hidenaga entrusted the project to his castle-building expert, Todo Takatora. Takatora carefully inspected the future castle site, personally drew up several designs, created a model of the planned castle, and took part in the work of laying out the grounds (nawabari). For the construction he brought in more than 10,000 workers and completed the large-scale project within a single year, which was considered extremely fast by the standards of the time.
Toyama Castle
Toyama Castle is located almost in the very center of the former province of Etchū and is surrounded by a wide plain with a large number of rivers. The very first castle on the banks of the Jinzu River was built in 1543 by Jimbo Nagamoto. The Jimbo clan were vassals of the Hatakeyama clan and governed the western part of Etchū Province. The eastern part of the province belonged to their rivals, the Shiina clan, who were also Hatakeyama vassals. Beginning in the 15th century, the influence of the ancient Hatakeyama clan gradually weakened, and as a result, the Jimbo and the Shiina fought constant wars for control of the province. Meanwhile, the forces of the Ikkō-ikki movement periodically intervened, helping first one side and then the other.
Takada Castle
During the Sengoku period, the lands where Takada Castle would later be built were part of Echigo Province and were controlled by the Uesugi clan.
Kishiwada Castle
The celebrated 14th-century military commander Kusunoki Masashige (1294–1336), who owned extensive lands south of what is now the city of Osaka, ordered one of his vassals, Kishiwada Osamu, to build a fortified residence. This order was carried out around 1336. These fortifications became the first structures on the site of what would later become Kishiwada Castle. From the beginning, the castle stood in a strategically important location—roughly halfway between the cities of Wakayama and Osaka, south of the key port of Sakai. Because of this position, it changed hands several times during periods of warfare.
Kaminoyama Castle
Kamino-yama Castle stood at the center of an important logistics hub, in the middle of the Yonezawa Plain, which served as the gateway to the western part of the Tohoku region. Roads connecting the Aizu, Fukushima, and Yamagata areas intersected here.
