Iwasaki Castle, often overlooked in history books and tourist guides, is located in modern-day Nisshin City, approximately 15 kilometers southeast of Nagoya City. Positioned on a hill, it offers clear views of the surrounding plain.
The castle is believed to have been built by Oda Nobuhide, father of Oda Nobunaga, in the early 16th century to protect his eastern borders and support his base at nearby Shobata Castle. In 1529, Matsudaira Kiyoyasu, Tokugawa Ieyasu’s grandfather, seized the castle by force. Six years later, Kiyoyasu was killed by one of his retainers during a misunderstanding, and his son, Matsudaira Hidetada (Ieyasu’s father), entrusted the castle to Niwa Ujikiyo.
Iwasaki Castle played a significant role in the Battle of Komaki and Nagakute in 1584. Ikeda Tsuneoki led the Toyotomi Hideyoshi forces against the Tokugawa-held castle. The Toyotomi strategy aimed to bypass Tokugawa lines and attack Ieyasu’s stronghold at Okazaki, making quick strikes on small castles along the way to confine them. However, at Iwasaki Castle, Ikeda’s forces were fired upon, and Tsuneoki himself was shot, falling from his horse. Enraged and humiliated, he commanded a full-scale assault. Despite a strong defense, the castle fell with heavy casualties, including over 300 dead. This delay allowed Ieyasu’s forces to catch up and defeat the Toyotomi at the Battle of Nagakute.
The Niwa clan held the castle for nearly 60 years until the Battle of Sekigahara in 1600, after which they were awarded a castle in present-day Toyota City, leading to Iwasaki’s abandonment. Reconstructed in concrete in 1987, the castle is now surrounded by two hectares of preserved parkland. Despite its visual appeal, the reconstruction is not historically accurate. An excavation revealed the remains of a well and a lookout tower. The structure below the keep now houses a museum dedicated to the history of the castle, the battle, and the Niwa clan.
See also
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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.
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Tsuyama Castle
Tsuyama Castle, located in Tsuyama City, Okayama Prefecture, is celebrated as one of Japan's top three major hilltop (Hirayama) castles, alongside Himeji and Matsuyama Castles. Originally, Tsuyama Castle comprised 77 structures, including the main keep, various yagura (watchtowers), gates, palaces, and living quarters. For comparison, Hiroshima Castle had 76 structures, and Himeji had 61. The first castle on this site was built in 1441 but was soon abandoned. The large-scale construction that we recognize today began in 1603 under the orders of Mori Tadamasa. The castle served as the administrative base for the Tsuyama Han daimyo, the Mori clan from 1603 to 1697, and the Matsudaira clan from 1698 to 1871.
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Tsu Castle
Tsu Castle, located in Tsu City, Mie Prefecture, was originally built by Hosono Fujiatsu in 1558 and was known as Anotsu Castle, named after the old region. The site was strategically chosen at the confluence of the Ano and Iwata Rivers, which naturally formed a moat around the castle, while the nearby port served as a vital trade route.
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Sasayama Castle
Tamba Sasayama Castle, also known as Sasayama or Kirigajo (Mist Castle), is a flatland castle (hira-jiro) situated on a gentle rise in the Tamba region of Hyogo Prefecture. It was constructed in 1608 as part of Tokugawa Ieyasu's strategy to prepare for an attack on Osaka, aiming to bring an end to the Toyotomi clan. Ieyasu ordered the castle's construction using the Tenka Bushin system, engaging 20 former enemy daimyo and their forces to complete the complex within six months. This system kept the former enemies close and preoccupied, financially straining them and limiting their capacity for further conflict. The stones used in Sasayama Castle feature engravings called kokumon, indicating who made each part of the walls and preventing theft by other lords' men.
