Iwamura Castle

Timeline

1. ca. 1185

   Toyama Kagetomo founds Iwamura

   Toyama Kagetomo, eldest son of Minamoto no Yoritomo's vassal Kato Kagekado, takes up the Toyama estate in eastern Mino and builds a flatland stockade that becomes the seat of the Iwamura Toyama clan.

2. 1337

   Castle of Mist named in the Taiheiki

   An entry in the Taiheiki on the battle at Kanegasaki names 'Toyama Saburo of Mino Castle of Mist,' the earliest written sign that a Toyama castle on this ridge was already known across the provinces.

3. 1572

   Otsuya-no-kata becomes female castellan

   After lord Toyama Kageto dies of illness, Oda Nobunaga's aunt Otsuya-no-kata takes charge of the castle as regent for the infant adopted heir Boshimaru, Nobunaga's fifth son.

4. 1573

   Surrender by marriage to Akiyama

   Besieged by the Takeda retainer Akiyama Torashige while Nobunaga could not relieve her in time, Otsuya-no-kata surrenders on the condition of marrying her besieger, and Iwamura passes under Takeda control.

5. 1575

   Nobunaga retakes Iwamura; crucifixions

   After the Takeda are broken at Nagashino, Nobutada leads a six-month siege to retake the castle; Nobunaga then rescinds the quarter and has Akiyama and Otsuya-no-kata crucified upside-down on the Nagara riverbank.

6. 1582

   Headquarters for the Kai campaign

   Nobunaga receives reports of his Kai campaign from Iwamura; after Takeda are extinguished, Kawajiri Hidetaka becomes castellan, and Dan Tadamasa is killed within months by the Honnoji Incident.

7. 1601

   Matsudaira Ienori founds Iwamura Domain

   After Sekigahara, Matsudaira Ienori enters Iwamura and founds Iwamura Domain (20,000 koku), moves the lord's residence from the summit to the foot, and lays out the castle town.

8. 1702

   Founding of the Chishinkan domain school

   Matsudaira Norinori enters from Komoro in Shinano and establishes the Bunbusho, later renamed Chishinkan, only the third domain school in Japan and the cultural anchor of eastern Mino.

9. 1718

   Toyama earthquake and repair drawings

   The Toyama earthquake of the seventh month of Kyoho 3 damages over fifty sections of stone wall; lord Matsudaira Norikata's repair drawings survive as Gifu prefectural cultural properties.

10. 1873

    Abolition order and dismantling

    Under the Meiji abolition order all wooden buildings of Iwamura are dismantled, leaving only stone walls; several gates including the Fumei-mon and the Toki-mon survive as temple gates in the town below.

11. 1990

    Residence buildings rebuilt in timber

    At the foot of the mountain, the Omote-gomon front gate, hira-shigeto secondary gate and taiko-yagura drum tower of the daimyo residence are rebuilt in timber, restoring the Edo entrance after 120 years.

12. 2006

    Japan 100 Famous Castles inscription

    Iwamura is selected for the Japan 100 Famous Castles by the Japan Castle Foundation, complementing earlier listings as one of the three great mountain castles and one of the 100 Hidden Landscapes of Japan.

Detailed History

Iwamura's history begins around 1185, when Toyama Kagetomo, eldest son of Minamoto no Yoritomo's vassal Kato Kagekado, was sent to the Toyama estate in eastern Mino and built an early stockade on the flatland below the ridge. The transformation into a full mountain castle came only in the late sixteenth century, jointly under the Iwamura Toyama and the invading Takeda. A 1337 entry in the Taiheiki, naming 'Toyama Saburo of Mino Castle of Mist,' shows a Toyama castle on this ridge already known across the provinces. In 1570 the Takeda retainer Akiyama Torashige struck east, defeated at Kamimura by the Oda commander Akechi Mitsuyuki. Two years later lord Toyama Kageto died of illness, and Oda Nobunaga installed his fifth son, the boy Boshimaru, as adopted heir, with his own aunt Otsuya-no-kata acting as regent female castellan. Linked with Takeda Shingen's Totomi campaign, Akiyama besieged Iwamura again, and Otsuya-no-kata surrendered on the condition of marrying him. The castle passed under Takeda control. After Katsuyori broke at Nagashino in 1575, Nobunaga sent his heir Nobutada to retake the ridge in a six-month siege. The promised quarter was rescinded; Akiyama, Otsuya-no-kata and three others were crucified upside-down on the Nagara riverbank. Iwamura then passed through Oda allies Kawajiri Hidetaka and Dan Tadamasa, both dying within months. Mori Nagayoshi and then his son Tadamasa took it, and senior retainer Kagami Mototada spent some seventeen years turning Iwamura into a modern stone-walled castle. In 1601, after Sekigahara, Matsudaira Ienori founded Iwamura Domain (20,000 koku), moved the lord's residence from the summit to the foot and laid out the castle town. Niwa rule from 1645 was followed in 1702 by the return of the Ogyu-Matsudaira under Norikata, who founded Chishinkan, only the third domain school in Japan. The Hoei earthquake of 1707 and the Toyama earthquake of 1718 damaged more than fifty sections of stone wall, prompting the famous repair drawings now held as Gifu prefectural cultural properties. The 1873 abolition order had every wooden building dismantled, leaving only stone. In 1990 the front gate and drum tower of the residence were rebuilt in timber, and in 2006 Iwamura was inscribed on the Japan 100 Famous Castles list.

Cultural Significance

Iwamura is counted, alongside Takatori in Nara and Bitchu-Matsuyama in Okayama, as one of Japan's three great mountain castles, with its main bailey at 721 meters above sea level the highest daimyo seat in the country. It also forms a regional trio with Naegi Castle in Nakatsugawa and Kaneyama Castle in Kani as the three mountain castles of Gifu, and is protected as a Gifu prefectural historic site. The nickname Kirigajo, Castle of Mist, comes from the autumn sea of clouds that hides the summit each dawn and symbolises the natural defence that confounded even Kamakura-era envoys. The tragic story of Otsuya-no-kata is preserved locally as 'Iwamura, village of the female lord,' and her name lives on in the local sake Onna-jōshu brewed by Iwamura Brewery, where corridor timbers from the main bailey survive in the brewery's hallway. The town centre is a nationally designated Important Preservation District (selected in 1998), with about 350 meters of Edo-period machiya lining the main street, and the front gate and Sekiten Hall of the Chishinkan school stand on the residence grounds as Gifu prefectural cultural properties. The site was added in 2006 to both the Japan 100 Famous Castles and the Japan 100 Hidden Landscapes, fixing its place as one of the country's most evocative encounters of Sengoku tragedy and mountain-castle scale.

Architectural Details

Iwamura's plan is a teikaku-style mountain castle climbing the city-named hill in concentric tiers. The main bailey at 721 meters is the highest daimyo seat in Japan and is ringed by a second bailey, a western demaru advance bailey, and a third bailey. There was no tenshu donjon; two-storey turrets stood on the main bailey, while a three-storey 'arrival turret' at the third bailey gate served as a substitute keep. The most celebrated feature is the six-tiered stone rampart on the north flank of the main bailey, where Mori-era engineers stacked steep cliff faces in six receding ledges. The face traces the evolution of Japanese stone-walling: rough nozura-zumi of natural stones at the lower courses, half-dressed uchikomi-hagi in the middle, and dressed kirikomi-hagi at the upper bands, spanning late Sengoku through early Edo. Senior retainer Kagami Mototada is credited with seventeen years of this transformation. As of the 1873 survey the main bailey held a yagura gate, a nando-yagura storehouse turret, east and west taman corridors, hira-shigeto and tana gates, while the second bailey added a hishi diamond turret, weapons and rice stores, and two-storey turrets. All wooden buildings were dismantled under the abolition order. At the foot the residence grounds regained their Edo frontage in 1990 with the timber rebuild of the front gate, hira-shigeto and taiko-yagura drum tower.