The Tokyo Bay Fortress is the group of artillery batteries constructed and deployed around the mouth of Tokyo Bay area to defend metropolis Tokyo and Yokosuka Naval Base from aggressors. This fortress construction started in Meij13(1880) firstly from No. 2 Kannonzaki artillery followed by that of No.1 and the first No.1 Sea Fort construction started in Meiji 14 (1881).
Then the Imperial Army decided to construct two sea forts between Futtsu Peninsula and Kannonzaki separating each other in equal distance of ca. 2.6km taking the effective firing range of cannons into their consideration.
These artillery batteries and sea forts were the pioneer of modern fortress constructions taking introducing modern western technology based on Japanese traditional technology.