The 1580 Battle of Omosu (Omosu no Tatakai) was one of many conflicts between the Hojo and Takeda clans during Japan's Sengoku period. What sets this battle apart is its rarity as one of the few naval engagements in pre-modern Japan. The conflict occurred off the coast of the Izu Peninsula, involving the fleets of Hojo Ujimasa, the leader of the Hojo clan, and Takeda Katsuyori, the head of the Takeda clan.
In a covert operation, the Fūma ninja, led by Fūma Kotarō, infiltrated and attacked a Takeda camp during the night. This surprise assault created chaos and confusion among the Takeda forces, leading them to turn on one another, causing significant casualties.
As the naval standoff continued, the land armies of both clans advanced towards each other. Ultimately, the Hojo clan emerged victorious.
See also
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The Second Siege of Gassan-Toda Castle (1564–1565)
Mori Motonari (1497–1571), head of the powerful Mori clan, was one of the most influential daimyo in the Chugoku region, located in western Honshu. During the turbulent and violent Sengoku Jidai period, he waged continuous wars in an effort to expand his domain and strengthen his clan's power.
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The Siege of Inabayama Castle
The two-week-long siege of Inabayama Castle marked the dramatic climax of Oda Nobunaga’s campaign to assert control over Mino Province and decisively crush the Saitō clan. It was during this operation that Toyotomi Hideyoshi, then known as Kinoshita Tōkichirō, first shone brightly in competition with Nobunaga—emerging as the future heir to Japan’s unification.
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The Siege of Wado Castle
In 1335, the Shiina clan built Uozu Castle as an auxiliary stronghold supporting Matsukura Castle. By 1570, it had fallen under the control of the Uesugi clan, rapidly emerging as a strategic fortress in Etchū Province. For many years, Kawada Nagataka served as its commander.
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The siege of the Ishimama Honganji monastery
In Japanese history, the siege of Ishiyama Hongan-ji — the main stronghold of the Ikkō-ikki movement during Oda Nobunaga’s campaign — is considered the longest, lasting from August 1570 to August 1580.
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The Battle of Norada
The Battle of Norada is a striking example of a clash during the Sengoku Jidai period, when numerical superiority did not always guarantee victory, even in open battle.
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Battles of Kawanakajima
The Battles of Kawanakajima were a series of fierce conflicts during Japan's Sengoku period, waged between Takeda Shingen of Kai Province and Uesugi Kenshin of Echigo Province from 1553 to 1564. These battles centered around the strategic Kawanakajima plain, lying between the Sai and Chikuma rivers in northern Shinano Province, now within Nagano City. The rivalry began when Shingen took control of Shinano, forcing Ogasawara Nagatoki and Murakami Yoshikiyo to seek refuge with Kenshin, prompting repeated clashes.
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Siege of Odawara 1590
The Third Siege of Odawara in 1590 was a pivotal moment in Toyotomi Hideyoshi's efforts to neutralize the Hojo clan as a challenge to his authority. In the months leading up to the siege, the Hojo made significant, hurried improvements to the castle's defenses as Hideyoshi’s intentions became clear. However, despite Hideyoshi's overwhelming force, there was little actual combat during the siege.
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Battle of Tenmokuzan
The Battle of Tenmokuzan in 1582 is remembered as the final stand of the Takeda clan in Japan. This battle marked the last attempt by Takeda Katsuyori to resist Oda Nobunaga's relentless campaign against him. Fleeing from his pursuers, Katsuyori set fire to his fortress at Shinpu Castle and sought refuge in the mountains at Iwadono, a stronghold held by his loyal retainer, Oyamada Nobushige. However, Oyamada betrayed Katsuyori, denying him entry. Left with no other option, Katsuyori committed suicide alongside his wife, while the remnants of his army made a valiant effort to hold off their attackers.
