Kushina Castle (1)
Alias: Shin-Shikano Castle
Location: Washimine, Shikano-cho, Tottori City, Tottori Prefecture, Inaba Province
Type: Mountain Castle
Remains: Kuruwa (enclosures), horizontal moats, vertical moats, horikiri (trench cuts), earthen ramparts, kirigishi (steep cliffs), koguchi (castle gates), foundation stone building sites, stone masonry, throwing stones, etc.
Main Castle Lords: Yamana clan (Tajima branch, Inaba Shugo), Amago clan, Mori clan, Kamei Korenori
Designation: No cultural property designations such as national, prefectural, or municipal historic sites.
──The "Other Shikano Castle" that emerged in Western Inaba
──A microcosm of the Inaba Sengoku history
Chapter 1: The Other Shikano Castle
The area around Shikano-cho, Tottori City, located in Keta District of Inaba Province, possesses complex terrain where four major valley lines (Osaka-dani, Katsu-dani, Mizuho-dani, and Hougi-dani) created by steep north-south mountain ridges and river erosion intersect like spread fingers. Because this limits visibility and movement in the flatlands, it was a significant challenge for the lord governing this region in terms of surveillance and defensive design.
The early modern Shikano Castle (elevation approx. 150 meters), located at the summit of Mt. Myoken overlooking the castle town, boasts a location as a base for governing the castle town and for provincial administration during peacetime. However, due to the influence of the mountain ridges blocking the east and west, the view from Shikano Castle was limited to the Mizuho-dani and Hougi-dani on the east side, and it was impossible to visually confirm movements in the Osaka-dani or Katsu-dani on the west side.
Kushina Castle, which stands on a ridgeline at an elevation of approximately 349 meters (approx. 350 meters), was constructed in a position to complement this blind spot in visibility. Kushina Castle is located at a higher elevation, retreated further south and behind Shikano Castle, ensuring a wide field of view that can overlook all four valleys that make up the Shikano district. Furthermore, the Kawachi-Miyasa Highway, a major trunk road connecting Inaba Province and Hoki Province, passes directly below, creating a structure that controls traffic on the national border. From Kushina Castle, it was possible to visually confirm Obata Takao Castle, which was a base for the Amago side, and Miyayoshi Castle of the Mori side, confirming that it played a role in wide-area control.
What becomes apparent from this geographical contrast is the reality that both castles were not competing entities, but rather in a "mutually complementary relationship": Shikano Castle, which was responsible for peacetime operations and castle town governance, and Kushina Castle, which was responsible for wartime bases, wide-area surveillance, and border defense.
[Shikano Castle (Mt. Myoken) - Kushina Castle (Northern foot of Mt. Washimine)]
Elevation and Site Occupation -Elevation approx. 150m (low mountain/adjacent to flat land) - Elevation approx. 349m (independent peak-like high ground)
Directly Visible Area -Shikano castle town, Mizuho-dani, Hougi-dani - Osaka-dani, Katsu-dani, Mizuho-dani, Hougi-dani (entire area)
Main Surveillance Targets -Castle town economy/administration, peacetime governance of the people - Kawachi-Miyasa Highway, Inaba-Hoki border, enemy castles (Obata Takao Castle, etc.)
Mobility and Defensibility -Easy access to the foot of the mountain, excellent mobility - Difficult to climb, but excellent in defensibility and wide-area visibility
Structural Division of Roles -"Castle that governs the castle town" (peacetime base) - "Castle that monitors and controls the entire region" (wartime base)
Chapter 2: Coexistence of a Combat Fortress and a Large Palace
A key feature of the structure of Kushina Castle is that fortress facilities and buildings serving as residences for high-ranking samurai coexist within a single enclosure. Surveys by the Tottori Prefectural Buried Cultural Property Center also evaluate this situation as a 'structural imbalance'.
Looking at the defensive design of the main castle, it was constructed with vigilance against enemy intrusion from the western slope. Directly below the enclosure, a box-moat-style 'horizontal moat' approximately 60 meters long was excavated, and 'vertical moats' were continuously integrated in a way that connects directly to it. This moat structure functioned as a shielded passage for soldiers within the castle while simultaneously having the effect of restricting the free movement of the attacking side in both vertical and horizontal directions. Furthermore, the perimeter of the main enclosure is covered by steep cliffs with height differences ranging from 4 to over 15 meters, and 'throwing stones (accumulations of river stones),' which are offensive projectile weapons, have been detected at a total of four locations on the cliff edges and earthen ramparts overlooking the enemy's approach routes.
In the highest enclosure (30 meters by 22 meters), located at the center of this tense combat environment, the remains of a large foundation-stone building were detected, measuring 5 bays in length (average column spacing of 197 cm) by 4 bays in width (average column spacing of 202 cm) with eaves on three sides. The scale of the main building alone, excluding the eaves, reaches 9.9 meters by 8.1 meters, and it is composed of rows of foundation stones with the flat surfaces of natural stones neatly facing upward. Since no roof tiles were included among the excavated artifacts, it is estimated that this building had a board-roofed or cypress-bark-roofed roof, and it has been determined that it was not a temporary barracks or warehouse, but a palace-style building for use as a meeting hall, main hall, or for conducting administrative affairs.
The format of placing such residential and administrative facilities in the main enclosure on the mountain summit is consistent with the evolutionary trajectory of mountain castles seen from the mid-to-late 16th century. As the power of the Sengoku daimyo strengthened, Kushina Castle tells the story of how mountain castles, which were previously merely temporary forts or military bases, transformed into 'political spaces' capable of demonstrating political prestige and conducting routine administration and receptions.
This building, equipped with eaves on three sides, is the first discovery of its kind in a Sengoku mountain castle within Tottori Prefecture, and it is highly likely that it was a residence for a Sengoku daimyo or a local lord-class individual.
Kushina Castle -Main enclosure (349m above sea level at the summit) - 5 bays x 4 bays (with eaves on three sides) - Non-tiled roof (estimated board/cypress bark roof) - Late 16th century (eve of the Toyotomi-Oda period mountain castle)
Shikano Castle -Nishinomaru (150m above sea level at the summit) - 8 bays x 7.5 bays - Tiled roof (drip tiles, tiles with Kobiki B marks) - Early 17th century (Kamei Korenori development period)
Shimizuyama Castle -Main enclosure (Shiga Prefecture, 210m above sea level) - 6 bays x 5 bays (with eaves on three sides) - Non-tiled roof (estimated board/cypress bark roof) - Late 16th century (Takashima Shichito Etchu clan period)
Chapter 3: The 'Three-Stage' Expansion Process Revealed by Excavation Surveys
Through the analysis of the intersection relationships of the remains obtained from excavation surveys, the analysis of embankment layers, and the chronological comparison of excavated ceramics, it is confirmed that Kushina Castle was not built in a single period, but was formed through at least 'three stages' of expansion and renovation in response to changing circumstances.
The first stageis the initial phase positioned from the mid-15th century to the first half of the 16th century. The remains of this period have enclosures left in the outer perimeter, consisting of small, stepped enclosure groups that utilized the undulations of the terrain as they were, and cliffs with low height differences and gentle angles. Excavated artifacts include Chinese celadon bowls from the late 15th century, Seto/Mino Tenmoku tea bowls, Bizen ware mortars, and earthenware plates with thread-cut bottoms, proving that a certain level of residence and daily life existed from this stage.
The second stageis the stage of large-scale fortification in response to the rising military tensions from the mid-to-late 16th century. Through this renovation, embankment modeling and leveling expansions were carried out, and at the same time, steep cliffs ranging from 7 to 15 meters in height were carved out around the enclosures. Furthermore, the construction of horizontal moats covering the western slope, continuous vertical moats, and the addition of earthen ramparts were carried out, significantly increasing defensive capabilities in combat, such as by forcing the siege route to the main area to make a long detour to the outer perimeter.
The third stageis the final development of the main enclosure and the addition of political functions in the late 16th century. The flat surface of the main enclosure was elaborately reconstructed, and a large foundation-stone building was constructed. Along with this, a slope-shaped entrance paved with flat stones connecting the enclosures was newly established, and a dignified approach to the palace was prepared.
Chapter 4: The End of the Inaba Yamana Clan and the History of Changing Ruling Powers
The transition of Kushina Castle vividly reflects the history of the turmoil that swept through Inaba Province from the end of the 15th century to the end of the 16th century.
According to documentary sources and traditions, it is said that around the 8th year of Oei (1401), Yukiyasu Sanjuro, the orphaned child of Yamana Mitsuyuki, built a castle on Mt. Washimine, and it is pointed out that it functioned as a base for governing Keta District under the power of the Tajima Shugo Yamana clan during the Eisho and Tenbun eras. It is believed that when Yamana Toyokazu and others, the Tajima-line Inaba Shugo, withdrew from Fuse Tenjinyama Castle in the 7th year of Eiroku (1564), the mountain castle in Shikano where they took refuge was this Kushina Castle during its renovation period. In other words, it can be inferred that this castle was the 'last mountain castle' in the process of the Inaba Yamana clan's authority collapsing.
After that, hegemony over Inaba moved rapidly to the Amago clan and then the Mori clan. In the 4th year of Genki / 1st year of Tensho (1573), Mori Terumoto ordered Nomura Shiezu, who was stationed at Shikano Mountain Castle, to rebuild it as a 'castle for partitioning Inaba and Hoki,' and it is presumed that the renovations leading from the second stage to the third stage were carried out by the Mori side during this period. The castle that was called 'Shikano' or 'Shikano Shin-yama' in primary historical sources at the time was the true identity of Kushina Castle.
Kamei Korenori, who entered Shikano under the Toyotomi administration as a general for the Oda side, carried out an attempt to give names related to Buddhism to the geography and castles within his territory. Along with Osha Castle (early modern Shikano Castle) and Kongo Castle, the name "Kushina Castle" was named after the ancient Indian Buddhist holy site "Kushinagara (Kushinagara)."
What is interesting here is the fact that roof tiles made using the "Kobiki B technique" used when the Kamei clan developed the early modern Shikano Castle during the Keicho era, as well as "drip tiles" from after the Korean expeditions, have not been excavated from Kushina Castle. This confirms that the foundation stone building in the main enclosure was constructed before the Bunroku Campaign (1592), that is, from the end of the Mori rule to the early period of the Kamei clan's entry (Tensho era). Therefore, it can be concluded that the remains of Kushina Castle were formed as a result of step-by-step renovations by each daimyo family, from the Yamana clan to the Amago clan, the Mori clan, and finally the Kamei clan, according to their own requirements.
Chapter 5: Summary - Supreme Value as a Complex Mountain Castle
The full picture of the Kushina Castle ruins holds an impact that shatters the view of mountain castles as mere local fortresses.
This castle shows a form that has come to fruition as a complex of "military, political, and residential" functions in the late Sengoku period, incorporating a political residence that embodies the authority of a Sengoku daimyo (third-stage large foundation stone palace) while maintaining its military nature as a fierce fighting castle (second-stage moats, steep cliffs, and throwing stones). Furthermore, its structural transition can be said to be a "microcosm of the Sengoku history of Inaba" that accurately records the dramatic change of lords in West Inaba from the twilight of the Yamana clan in the 15th century to the entry of the Kamei clan at the end of the 16th century.
The geographical environment where "two Shikano Castles"—the early modern Shikano Castle and Kushina Castle, which represents the culmination of medieval mountain castles—exist right under our noses is a rare cultural asset in the history of Japanese castles. Through the re-organization of excavated artifacts and further investigation of temple ruins at the foot of the mountain (such as the Hogetsu-ji temple ruins in Kobutsudani), it is expected that the mysteries of the Sengoku turmoil in West Inaba will be further unraveled in the future.
【Video of the Sengoku Mountain Castle Kushina Castle by the Tottori Prefectural Archaeological Center】
This content was created based on Gemini through repeated dialogue with the poster.
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