Lit.: "the island within the river"; a plain located in Shinano Province, very near modern Nagano, on which Takeda Shingen and Uesugi Kenshin fought five major battles in 1553, 1555, 1557, 1561 and 1564. In the battle of 1561, Takeda with 20,000 men won over Uesugi's force of 18,000. 12,400 and 12,960 men were lost by Takeda and Uesugi respectively, a loss of life greater than in any other battle in the Sengoku period