Yura Fortress
The Kitan Strait is of strategic significance because it controls access to Osaka Bay. When Japan started modernizing after the 1868 Meiji Restoration, it faced potential threats from Russia, China, and the colonizing Western powers, and in the 1890s it built three separate groups of fortifications to defend the strait. Collectively known as the Yura Fortress, they were located in Yura, a port on Awaji Island directly across the strait from here; on the four-island cluster known as Tomogashima that spans the strait; and in Miyama here in Kada. Redoubts were built further inland to protect the batteries from attack from the sea. Kada had five batteries, four redoubts, and a searchlight station on a coastal promontory. Tomogashima had five batteries and one redoubt, while Yura, where the garrison command was located, had seven batteries and three redoubts. The arrows indicate the direction of fire of the guns.
The Miyama batteries were incorporated into the Yura Fortress in 1899 after the passing of the Fortified Zone Act and Military Secrets Protection Act. These acts prohibited trespassing, photographing, or sketching in militarized areas, so Kada, Tomogashima, and Yura were completely off-limits to the public while the batteries were operational.
The information in this map comes from A History of Japanese Fortifications by Johoji Asami (1971).