Kanki Castle

• Alternative names: Manai Castle, Nakosho Castle

• Location: Kanki, Higashikanki-cho, Kakogawa City, Hyogo Prefecture (current area around Jorakuji and Shinshuji temples), Harima Province

• Type: Flatland castle (enclosed-style flatland castle)

• Remains: Most of the castle area has become a settlement, and there are no clear remains.

• Main castle lord: Kanki clan (a branch of the Akamatsu clan)

• Designation: No cultural property designations such as national, prefectural, or municipal historic sites

──A key point in Eastern Harima that drew out the entire main force of the Oda army
──Must not be dismissed as merely a "branch castle of Miki Castle"

Introduction: The overall picture of the Miki Campaign and the positioning of "Kanki Castle"

In the Harima Campaign led by Hashiba Hideyoshi, which unfolded from 1578 to 1580, the "Miki no Higoroshi" (starving out of Miki), where Miki Castle, held by Bessho Nagaharu, was besieged and starved, is known as a milestone in the history of warfare. However, in the understanding of later military chronicles, attention has focused solely on the defense of Miki Castle and the formation process of the "Miki-tsukishiro-gun" (group of siege castles around Miki), while the various castles of local powerful clans placed in the surrounding area have tended to be regarded as "vanguard bases subordinate to the main castle (Miki Castle)" or "branch castles that fell easily in the preliminary stages of the siege."

However, the development of recent castle archaeology and the critical analysis of primary historical sources such as the "Shinchoki" are overturning this conventional view. A case in point is "Kanki Castle," a flatland castle with a sogamae (outer enclosure) built on a terrace on the right bank of the Kako River.

The battle for Kanki Castle was more than just a skirmish at a local fortification. It was a "total war in Eastern Harima" where Oda Nobunaga gathered the main units of the Oda family, including his eldest son Nobutada, Akechi Mitsuhide, Niwa Nagahide, Takigawa Kazumasu, Araki Murashige, and Hosokawa Fujitaka, all in one place. Furthermore, the Oda army deployed the full extent of cutting-edge siege weapons and engineering tactics, including large cannons, watchtowers, tunnel excavation by miners, artificial hills, and filling materials.

This content will clarify the Eastern Harima defense line held by Kanki Castle, while also examining the advanced nature of its sogamae, which boasted impregnability despite being a flatland castle, the consistency between primary sources and archaeological remains, and the castle defenders Kanki Yorisada and Kanki Todayu as depicted in military chronicles such as the "Banshu Taiheiki."

Geographical selection and history of Kanki Castle

Kanki Castle is located in Kanki, Higashikanki-cho, Kakogawa City, Hyogo Prefecture, and was situated on the western edge of a terrace extending narrowly from east to west, sandwiched between the Kako River and the Hokesan-dani River. Despite being low-lying terrain with an elevation of about 13m and a relative height of about 3 to 8m, it was a location with natural advantages, accompanied by steep, cliff-like slopes in front and a wetland area on the lower terrace. The ancient Sanyo-do road and the early modern Saigoku-kaido road ran just to the south of the castle, and the Kako River, an artery for north-south water transport, flowed to the east, allowing Kanki Castle to function as a node controlling both land and water distribution and military movement lines.

There are multiple conflicting traditions regarding the construction period and early history of Kanki Castle, and views differ depending on the historical source. While it is common knowledge that the Kanki clan, a branch of the Akamatsu clan, resided there for generations, theories range from construction by Akamatsu Noritsugu (Kande Shikibu-no-Taifu Motomori) during the Northern and Southern Courts period to theories of restoration during the Bunmei era after the Onin War.

• Akamatsu Shoke Taikeifu (Genealogy of Akamatsu Branches) / Nihon Jokaku Taikei (Compendium of Japanese Castles) -Bunwa era (1352–1355) Akamatsu Noritsugu (Kande Shikibu-no-Taifu) - A theory that Noritsugu, the eldest son of Akamatsu Mitsunori, took possession of Kanki-no-sho and built the castle. His descendants took the name Kanki and achieved military merit for the Shogunate.

• Kanki-mura Zatsunoroku (Miscellaneous Records of Kanki Village) / Nihon Jokaku Zenshu (Complete Collection of Japanese Castles) -Bunmei 1st year (1469) Kande Shikibu-no-Taifu Motomori - A theory that he took possession of 10,000 koku in Kanki-no-sho due to his merit in the vanguard and built the castle. After the Onin War, he restored it and organized the Honmaru, Ninomaru, Nakamaru, and Nishinomaru.

• Miki Senki (Chronicle of the Miki War) -Kenmu era (1334–1338) Akamatsu Suketoshi - A theory that Akamatsu Suketoshi was granted Kanki-no-sho for his military service during the Kenmu era and built the castle. It continued for 11 generations and 220 years thereafter.

• Kakogawa City History (Ishino Genealogy / Inryoken Nichiroku) -Muromachi period (15th century) Akamatsu Norizane (Minbu-no-Shoyu) - Genealogy of Yutoshi (Dairin), grandson of Akamatsu Norisuke. Recorded in the entry for Bunmei 18 (1486) that "the four families of Shikata, Nakamura, Eho, and Kanki are of the same surname."

Although various traditions exist, all historical documents tell the history of the Kanki clan as a prestigious family of the Akamatsu clan, deeply rooted in the Kakogawa River basin of eastern Harima, establishing regional dominance while coordinating with the Bessho clan and the main Akamatsu family.

Geopolitical and strategic value in the eastern Harima defense line

In the early stages of the Miki Campaign, the forces of Nagaharu Bessho constructed a wide-area defense line connecting the four castles of eastern Harima—Kanki Castle, Noguchi Castle, Shikata Castle, and Takasago Castle—functioning as a breakwater against the Oda army from the west.

• Kanki Castle - Higashikanki-cho, Kakogawa City - Control of Kakogawa water transport and the Sanyo Road, a field defense base using a 'sogamae' (outer enclosure) - Its fall led to the breakthrough of the center of the defense network and the severance of the western supply line to Miki Castle.

• Shikata Castle - Shikata-cho, Kakogawa City - A rear support and communication base located 2.6 km north of Kanki Castle - Opened its gates and surrendered under pressure from the Oda army the day after Kanki Castle fell.

• Noguchi Castle - Noguchi-cho, Kakogawa City - The frontline outpost of eastern Harima - The first to be captured by the Oda army's initial offensive.

• Takasago Castle - Takasago-cho, Takasago City - A port base for receiving maritime supply networks facing the Harima Sea - Neutralized in conjunction with the fall of Kanki Castle and Shikata Castle.

In March of Tensho 6 (1578), Hideyoshi Hashiba began the siege of Miki Castle, but the fortress was well-defended, and he struggled to make progress. In response, the Bessho side planned a pincer attack in coordination with the various castles of eastern Harima. Late on the night of April 4, Tensho 6, Yorisada Kanki, lord of Kanki Castle, personally led over 300 men to sortie toward Miki Castle, joining forces with the lords of other castles (totaling about 1,000 men) at Omurazaka. On the night of April 5, they launched a simultaneous attack on Hideyoshi's camp, dealing a significant blow to the Oda army.

Taking this defeat seriously, the Oda army temporarily abandoned the offensive against Miki Castle and changed its strategy to a phased siege, aiming to 'chip away at the surrounding strong branch castle defense line one by one to completely isolate Miki Castle.' In parallel with the capture of eastern nodes centered on Awaga Castle and religious cities and distribution routes such as Mt. Shosha and Mt. Niu, Kanki Castle emerged as a target for the Oda army, standing as a barrier after the fall of Noguchi Castle. Kanki Castle was not merely a satellite for the defense of Miki Castle, but a vital point holding its fate, as 'if this castle falls, the defense line of eastern Harima will collapse, and the complete isolation of Miki Castle will be achieved.'

'It doesn't fall despite being a flatland castle': The fusion of advanced 'sogamae' and natural terrain

In the common understanding of medieval castles, mountain castles (fortresses) were considered to have superior defensive capabilities compared to flatland castles. However, Kanki Castle, despite being a flatland castle, held back the large Oda army for several weeks and inflicted massive damage. The source of its defensive power lay in the fusion of natural low-lying wetland terrain and an advanced 'sogamae' (outer enclosure).

The layout of Kanki Castle was a complex fortification that surrounded the main enclosure group (main castle) with dry moats, steep cliffs, and waterways, and further incorporated villages and farmland into an 'outer enclosure (sogamae).' The description of the castle structure recorded in the primary source 'Shinchō Kōki' matches the reconstruction diagrams based on modern micro-topographical analysis (such as the 'History of Kakogawa City' and surveys by the Hyogo Prefectural Board of Education).

The 'main castle' appearing in 'Shinchō Kōki' corresponds to the central section composed of enclosures in the ruins survey, and the steep cliffs and moats surrounding it formed the defense line as the 'moat of the main castle.' The main enclosure (site of Joraku-ji Temple) corresponds to the 'Naka-no-Maru' (command center), the enclosure to its west (site of Shinshu-ji Temple) corresponds to the 'Nishi-no-Maru,' and the enclosure corresponds to the 'Higashi-no-Maru.'

The 'outer enclosure' that surrounded the further outside of the castle was a structure that collectively enclosed the entire fields and villages spreading from the west to the south of Kanki Castle at the time with waterways, dry moats, and earthworks, showing an advanced 'sogamae' structure that leads to the defense of castle towns in the early modern period.

Also, in the entry for July 16, Tensho 6 in 'Shinchō Kōki,' there is a description: 'Attacked into the Naka-no-Maru, killed Minbu-no-Shoyu Kanki, and set fire to the Tenshu, burning it down.' While there is debate over whether this 'Tenshu' was a multi-story castle tower of later generations, it indicates that a complex turret equipped with symbolic architecture or command functions was towering in the Naka-no-Maru at the time, telling of the Kanki clan's excellent technical and economic foundation.

The Oda army's total war: Excessive firepower and 'comprehensive siege weapon testing ground'

The scale of the Oda army deployed for the siege of Kanki Castle far exceeded what was necessary to attack a local flatland castle.

Commander-in-Chief

• Oda Nobutada

Oda Clan Members

• Oda Nobukatsu

• Oda Nobukane

• Oda Nobutaka

Famous Generals and Senior Retainers

• Akechi Mitsuhide

• Niwa Nagahide

• Takigawa Kazumasu

• Hosokawa Fujitaka

• Araki Murashige

• Inaba Ittetsu

• Ujiie Naomichi

• Ando Morinari (Mino Triumvirate)

• Sakuma Nobumori

• Hayashi Hidesada

• Tsutsui Junkei

• Hachiya Yoritaka

• Shunhide Muto

and other core famous commanders and senior retainers of the Oda clan were all included.

The background to the Oda army deploying such an excessive, massive force (over 30,000) included not only the disgrace at Omurazaka in April, but also the tension caused by the Mori clan's approach to Harima and the anti-Nobunaga encirclement network formed by the Ishiyama Hongan-ji and the Uesugi clan. Stagnating at Kanki Castle would have meant the defection of the local lords throughout Harima, so it was necessary to demonstrate military power and quickly crush the encirclement.

In the general offensive that began on June 27, Tensho 6, the Oda army deployed every latest siege technology and engineering weapon conceivable in the Sengoku period. The Battle of Kanki Castle was, in effect, an 'experimental ground for the Oda army's cutting-edge siege weapons.'

Nagahide Niwa, Kazumasu Takigawa, and others constructed two tall 'Joro (large, modular siege towers for shooting)' at the east gate and the southeast part of the castle, and from them, they fired 'Oteppo (large-caliber matchlock guns)' repeatedly into the castle, destroying walls and turrets. Additionally, Kazumasu Takigawa's unit mobilized miners (mining engineers) to dig tunnels from underground into the castle, attacking the base of the turrets from both above and below ground to burn them down.

For the castle's moat, which was blocked by wetlands and dry moats, they threw in large quantities of 'umekusa' (filling material made of grass, trees, and earth) to fill it in. Furthermore, they used rapid construction to build 'tsukiyama' (artificial mounds) as shooting positions overlooking the interior of the castle. Against the intense fire from the defenders, they adopted a close-quarters tactic of pushing 'take-束' (bamboo bundles), which served as bulletproof shields, to the front lines, gradually closing in on the castle walls.

The truth of the 'fall of the castle' legends dismantled through historical source criticism

Regarding the fall of Kanki Castle, there are discrepancies between the descriptions in military chronicles compiled in later ages and contemporary primary sources. By dismantling and reconstructing this dissociation from the perspective of historical source criticism, the true reality of the castle's fall emerges.

【Primary Source: 'Shinchoki' - Military Chronicles: Descriptions in 'Banshu Taiheiki', etc. - Verification by Modern Historiography (Kakogawa City History, etc.)】

• Siege Tactics -Approaching using bamboo bundles, filling the moat, and attacking with large matchlocks from artificial mounds and siege towers. - A special tactic called 'Choda-kuzushi' (Long Snake Collapse), where soldiers were placed inside giant tubular bamboo structures. - 'Choda-kuzushi' is a later creation and embellishment. The historical reality was standard bamboo bundle approaches and a war of attrition.

• Movements of Totayu Kanki -Holed up in the West Bailey. After the main castle fell, he was pardoned and left through the mediation of Murashige Araki and Nobumori Sakuma. - A great villain who responded to Hideyoshi's bribery, assassinated the lord Yorisada, and sold the castle. - The reality was a fall due to a war of attrition that could not be matched. Totayu's betrayal and assassination are fictional creations in the stories.

• Factors of the Fall -Destruction through artificial mounds, large matchlocks, tunnel excavation, and continuous assaults on the East and Middle Baileys. - Self-collapse due to internal collusion and assassination. - The result of the Oda army's overwhelming material superiority and forceful tactics using engineering weapons.

In military chronicles such as 'Banshu Taiheiki', a special operation where soldiers were hidden inside giant bamboo tubes made from bamboo cut from the Kakogawa riverbed to advance is called 'Choda-kuzushi' and is exaggerated as a brilliant strategy by Hideyoshi. However, 'Shinchoki' only contains descriptions of standard siege weapons like bamboo bundles, and there is no mention of the name 'Choda-kuzushi' or any such bizarre weapons.

An even greater distortion of historical fact is seen in the movements of Totayu Kanki, the uncle of the lord Yorisada. In military chronicles, Totayu is depicted as a 'great villain' who, blinded by rewards, assassinated Yorisada and surrendered by offering his head. However, according to 'Shinchoki', Totayu continued to hole up and resist in the West Bailey until the very end. After the Middle Bailey fell and Yorisada was killed in battle, he made a 'plea for surrender' through Nobumori Sakuma and Murashige Araki, with whom he had previously been acquainted, and was formally pardoned before leaving the castle. Records such as 'Buko Yawa' also state that Totayu led his subordinate soldiers to Shikata Castle and Miki Castle to continue the resistance.

In academic research, it has been concluded that the fall of Kanki Castle was not due to internal assassination plots, but rather the result of the Oda army's overwhelming material superiority and engineering weaponry. The betrayal of Todayu found in military chronicles is merely a creative invention that transformed the tragic historical reality of the siege into a morality play of a 'tragic young warrior (Yorisada) and a despicable traitor (Todayu).'

From Defeated General to Renowned Commander: The Assessment of Yorisada Kanki and the End of the Eastern Harima Defense Network

The lord of Kanki Castle, Minbu-no-Shoyu Yorisada Kanki, was a young warrior of only 29 at the time of the battle in the 6th year of Tensho (1578). In traditional narratives, he has often been treated as a 'local warlord who was instantly defeated by a massive army,' but when tracing the casualties on the Oda side and the progression of the battle, the true image of Yorisada as an outstanding commander emerges.

While the Kanki Castle garrison consisted of approximately 2,000 soldiers, the attacking Oda army was a massive force exceeding 30,000. Despite a 15-fold difference in troop strength, Yorisada repelled the Oda army's vanguard, the Nobutaka Kanbe unit, preventing an immediate capture on the first day, and further depleted the Oda army's firepower by deploying blinding sand and engaging in close-quarters combat at the moats.

According to records such as the 'Honganji Kennyo Letter' and the 'Ietada Diary,' it is proven that the Oda army suffered numerous casualties in the fighting from June 26th through July, and that Kazumasu Takigawa, a senior retainer of the Oda clan, was himself wounded. Yorisada, who held back the main force of the Oda clan for nearly three weeks with only 2,000 soldiers and inflicted damage on the attackers, should be evaluated as a renowned commander rather than a 'defeated general.'

On July 16th, in the 6th year of Tensho, after intense fighting, the keep of the inner bailey (Naka-no-maru) caught fire, and Kanki Castle fell. Yorisada died in battle in the inner bailey, and the siege reached a tragic conclusion with the majority of the garrison killed in action or burned to death.

The fall of Kanki Castle triggered a chain reaction in the war situation of Eastern Harima. The news that Kanki Castle had been breached shocked Masayasu Kushihashi, lord of Shikata Castle to the north, and when the Oda forces pushed toward Shikata Castle the following day on the 17th, the Shikata side, realizing resistance was impossible, immediately surrendered hostages and opened the gates. Takasago Castle to the south was also isolated and surrendered after its supply lines were cut, causing the Eastern Harima defense line to collapse in an instant. The capture of Kanki Castle was the turning point that completed the Miki Castle encirclement (the 'starving out of Miki').

Conclusion: The Legacy of Kanki Castle, a Pioneer of the Sogamae Flatland Castle

The Battle of Kanki Castle holds historical facts that rewrite the traditional interpretation of it being a 'subordinate branch castle hidden in the shadow of Miki Castle.' Kanki Castle was not merely a forward outpost; it was a core hub of a wide-area defense line that controlled the Kakogawa water transport and land routes, supporting the entirety of Eastern Harima alongside Noguchi, Shikata, and Takasago castles.

In an era where mountain castles were dominant, the fact that it achieved impregnable defensive capabilities as a flatland castle by adopting 'Sogamae' (comprehensive enclosures) that included natural low-lying wetlands, artificial steep cliffs, dry moats, and settlements, marks the culmination of castle development history in Eastern Harima. Furthermore, it stands out in the history of Sengoku battles as a 'cutting-edge siege weapon testing ground' where the Oda army's boasted military engineering and material tactics—including large iron cannons, castle towers, mining tunnels, artificial mounds, and bamboo bundle approaches—were fully mobilized.

When the fiction of the 'betrayal and assassination plot' fabricated by military chronicles is discarded, the true pride and fierce fighting of the Kanki clan, including Yorisada Kanki and Todayu, who engaged in a bloody battle against a massive army and advanced weaponry, rightfully emerge. Today, the remains of Kanki Castle are buried in the residential areas of Kakogawa City and the grounds of Joraku-ji and Shinshu-ji temples, but the tombstone of Yorisada Kanki standing at Joraku-ji, the stone monuments of the clan, and the subtle micro-topography of the original layout quietly convey the spectacular memory of the Sogamae flatland castle that mobilized the main forces of the unifiers Nobunaga Oda and Hideyoshi Hashiba.

This content was created based on Gemini and through repeated dialogue with the contributor.

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