Battle of Omosu

Battle of Omosu
Date March 1580 Location Suruga Bay, Izu Province 35°01′12″N 138°53′17″E Result Hōjō victory
Belligerents
Hōjō forces	Takeda forces
Commanders and leaders
Hōjō Ujimasa Fūma Kotarō	Takeda Katsuyori Ohama Kagetaka
class=notpageimage| Location within Shizuoka Prefecture Battle of Omosu (Japan)

The 1580 battle of Omosu (重須の戦い, Omosu no Tatakai) was one of many battles fought between the Hōjō and Takeda clans during Japan's Sengoku period. It is distinguished, however, as one of the very few naval battles to be fought in pre-modern Japan.

In 1580, after Takeda Katsuyori joined the force to support Uesugi Kagekatsu and forced Uesugi Kagetora killed himself, later Ujimasa built a new alliance with Oda Nobunaga and Tokugawa Ieyasu. Ujimasa invaded the territory of the Takeda clan in Suruga from both sides attacked Katsuyori, which triggered the Battle of Omosu.

The battle took place off the coast of the Izu peninsula between the navies of Hōjō Ujimasa, the head of the Hōjō, and those of Takeda Katsuyori, the head of the Takeda. While the navies battle faced off, the land armies of each clan advanced towards one another. In the end, the Hōjō were victorious.

Popular Culture

During the battle, the Fūma ninja led by Fūma Kotarō covertly infiltrated and attacked a camp of the Takeda clan forces at night, succeeding in causing severe chaos in the camp, which resulted in massive casualties among the disoriented enemies as they attacked each other.