A Fortified District refers to the Japanese Army and in certain cases the Japanese Navy defensive fortified organization in World War II. It was created in the districts of Manchukuo; Chosen in Korea; Karafuto; Southern Sakhalin and the Kurile Islands - a front of over 6,000 kilometers.
The Japanese forces had built 17 "fortified districts" and over 4,500 permanent emplacements along the USSR border. Other similar structures were constructed inland in these provinces. In similar form it organized other fortified districts inside mainland Japan (coastal and inner mountainous areas) and overseas provinces (Formosa, Ryukyu, South Pacific Mandate, etc.)
Such installations that were constructed for defensive/offensive purposes were used by both sides. They were designed by the Japanese and used by the Russians during 'August Storm' operations in August 1945, when fire from heavy guns on land and coastal Tochkas was used against Japanese forces.
Examples of heavy Japanese fortified artillery:
Type 94 37mm anti-tank (AT) GunType 1 37mm AT GunType 1 47mm AT GunType 92 70mm Infantry GunType 98 20mm AA CannonType 2 20mm AA CannonType 4 20mm AA Twin CannonType 11 75mm AA GunType 88 75mm AA GunType 4 75mm AA GunType 99 88mm AA GunType 14 10 cm AA GunType 3 12 cm AA GunType 5 15 cm AA Gun (Kugayama Cannon)28 cm Heavy HowitzerType 38 15 cm HowitzerType 45 24 cm HowitzerType 45 15 cm GunType 7 30 cm HowitzerType 7 10 cm GunType 7 15 cm GunType 11 75mm GunType 89 15 cm GunType 96 24 cm HowitzerType 96 15 cm GunExperimental 41 cm HowitzerType 90 24 cm Railway Gun (Futtsu Cannon)and other types of special heavy artilleryExamples remain in:
Chosen Fortifications:Seishin (now Chongjin) with 4,000 officers and men, protected by heavy coastal artillery, an armored train, a regular train carrying combat equipment, and eight concrete fortifications and emplacements.Etetin (now Odetsin)Genzan (now Wonsan) with 6,238 Japanese officers and soldiersRashin (now Najin)Yuki (called Unggi in Korean, now called Sonbong, or "Vanguard" in North Korea.)Manchoukouan Fortifications:ManchouliKotouFuyuanSungari and the Japanese Army Sungari FlotillaHsinking fortified district/defense centerTuntsiang defense centerFutsing fortified district with five permanent emplacements, a munitions depot and six mortar batteries.Sun’u with 20,000 Japanese officers and soldiersSansingKwantung Fortifications:Port Arthur (now Liaoshun)Dairen (now Dalian)