Oiwayama Fort

The castle site itself is quite small and requires only about 20 minutes to view it in its entirety. To reach the castle you need to either hike 2km downhill from Shizugatake Fort or 1.1 km up from Iwasakiyama Fort. The main enclosure is well maintained and signposted but the side baileys a

History

Oiwayama Fort was the middle of three key mountaintop positions in Hideyoshi’s second defensive including Shizugatake Fort.

The fort was commanded by Nakagawa Kiyohide (中川清秀), one of Hideyoshi’s most trusted retainers. On the morning of April 20, Shibata Katsuie’s general Sakuma Morimasa (佐久間盛政) launched a bold flanking attack, bypassing the well-defended Shizugatake summit and striking directly at Ōiwayama via the lakeside route. In a brutal and chaotic fight, Nakagawa was killed in action, making Ōiwayama Fort the first and only major position on Hideyoshi’s line to fall during the battle.

The loss of Kiyohide was a heavy blow, but it also triggered Hideyoshi’s famed counteroffensive. On his return from Ogaki, Hideyoshi quickly assessed the situation, gathered his troops at Tagamiyama Fort, and launched a rapid pursuit that routed Sakuma’s forces and turned the tide of the campaign.

Field Notes

The castle site itself is quite small and requires only about 20 minutes to view it in its entirety. To reach the castle you need to either hike 2km downhill from Shizugatake Fort or 1.1 km up from Iwasakiyama Fort. The main enclosure is well maintained and signposted but the side baileys are overgrown and hard to get into.

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Gallery

Nakagawa Kiyohide's grave

Castle Profile
English Name	Oiwayama Fort
Japanese Name	大岩山砦
Founder	Toyotomi Hideyoshi
Year Founded	1583
Castle Type	Mountaintop
Castle Condition	Ruins only
Historical Period	Pre Edo Period
Features
Visitor Information
Access	JR Yogo Station
Hours	mountain trails, well signposted
Time Required	20 mins
Location	Nagahama, Shiga Prefecture
Coordinates	35.52077, 136.20507
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Admin
Added to Jcastle	2025
Contributor	Eric
Admin Year Visited	2024
Admin Visits	April 29, 2024
Friends of JCastle
Jokaku Horoki

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