Iwakura Castle was a hira-jiro, or flat-land castle, located in the plains that would become Iwakura City, Aichi Prefecture. At one time, it rivaled Kiyosu Castle in size and stature. Constructed in 1479, it covered an area of 900 meters north to south and 400 meters east to west. Two sets of moats encircled the castle: the outer moat, about 10 meters wide, and the inner moat, about 15 meters wide, separated by a 10-meter-wide strip. These moats surrounded the Honjo, or main castle precinct, which measured about 170 meters north to south and 90 meters east to west. To the north and directly east of the castle flowed the Gojo River.
The castle's Ote-mon, or main gates, faced southeast, with the rear gates to the north. Directly south and to the northeast were large areas, roughly the size of the central precinct, designated for samurai housing.
During the Sengoku period, Owari Province was ruled by two main factions of the Oda clan. The Iwakura Oda clan held the northern districts of Owari, while the Kiyosu Oda clan ruled the southern areas. The famed Oda Nobunaga belonged to the Shobata Oda clan, a branch of the Kiyosu Oda family.
Nobunaga increased his power by defeating and overtaking the Kiyosu Oda. In opposition, the Iwakura Oda formed an alliance with Nobunaga's brother, Nobuyuki. However, they were defeated by Nobunaga at the Battle of Ukino in 1558, after which Iwakura Castle was attacked.
In June 1558, Oda Nobunaga surrounded Iwakura Castle with palisades, set the castle town ablaze, and placed it under a siege that lasted for two to three months. During the ensuing battle, Yamauchi Moritoyo, a vassal of the Iwakura Oda, was killed. His son, Katsutoyo, was temporarily unemployed until joining Nobunaga’s forces around 1567, later becoming the master of Kakegawa and Kochi Castles.
Nobunaga continuously launched fire-arrows and fired rifles into the castle, employing various tactics to wear down the defenders. Eventually, the besieged Iwakura forces found it too difficult to hold the castle and decided to surrender. The defenders left and dispersed, and shortly thereafter, Nobunaga had the castle destroyed, returning to his castle at Kiyosu, having achieved the unification of Owari Province.
Unfortunately, nothing remains of Iwakura Castle except for a monument standing on the site of the rear gates to the main enclosure.
See also
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Shinpu Castle
Shinpu Castle was a Japanese hirayama-style fortress from the Sengoku period, situated in what is now Nirasaki, Yamanashi Prefecture. It served as the main stronghold of warlord Takeda Katsuyori. Designated as a National Historic Site in 1973, the castle occupies a strategic position on a mountain with steep cliffs, overlooking the Kamanashi River to the west of Kofu, where Takeda Shingen’s Tsutsujigasaki Castle once stood.
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Takato Castle
Takato Castle, located in the city of Ina in southern Nagano Prefecture, Japan, was a notable stronghold during the Sengoku period. By the end of the Edo period, it was the residence of a cadet branch of the Naito clan, the daimyo of the Takato Domain. Also known as Kabuto Castle, it was originally constructed in the 16th century and is now mostly in ruins.
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Takatenjin Castle
Takatenjin Castle was a yamashiro-style fortress from Japan's Sengoku period, situated in the Kamihijikata and Shimohijikata districts of Kakegawa, Shizuoka Prefecture. Designated a National Historic Site in 1975, with an expanded protected area in 2007, its ruins remain a significant historical landmark.
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Yoshida Castle
Yoshida Castle is renowned worldwide, particularly through the intricate woodblock prints by Edo Period artist Hiroshige. His famous series, depicting the 53 stages of the Tokaido—the historic route between Kyoto and Edo (modern-day Tokyo)—includes the 34th print, which shows workmen repairing a castle overlooking a wooden bridge crossing a wide river. This scene captures the Toyokawa River at Toyohashi in southeast Aichi Prefecture, and the castle is Yoshida Castle.
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Yamato Koriyama Castle
The impressive ruins of Koriyama Castle sit atop a small hill, surrounded by two rivers. The strategic positioning and strong layout of the castle served it well through the final years of the Sengoku period and the peaceful days of the Edo period.
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Yamanaka Castle
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.
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Uwajima Castle
Uwajima Castle, located in Uwajima City, Ehime Prefecture, Shikoku, is one of the 12 remaining Japanese castles with an original keep. Known for its small size, Uwajima Castle is relatively difficult to access, which means it is less frequented by tourists.
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Ueda Castle
Ueda Castle in Nagano Prefecture once stood prominently on a cliff overlooking the Saigawa River. Also known as Amagafuchi-Jo, Isesaki-Jo, Matsuo-Jo, and Sanada-Jo, it was built around 1583 by its first master, Sanada Masayuki. This sturdy yet small fortress cleverly utilized the surrounding natural defenses, including the river, steep rocky cliffs, the layout of the town below, and the strategically designed waterways to hinder attackers. Ueda Castle was fortified with seven defensive yagura (watchtowers) atop robust stone walls and had two large gates with watchtowers above them.
