KURE 1 NOVEMBER 1945
Interrogation of: Captain MINAMI, Rokuemon, IJN; with the First Escort Fleet in TAKAO and MOJI, and on the Staff of the Seventh Fleet.
Interrogated by: Commander T. H. Moorer, USN.
Captain MINAMI discusses the problems encountered by the Seventh Fleet during the mining attack against the SHIMONOSEKI Straits. Some information relative to the effect of mining attacks made against FORMOSAN and CHINESE ports is also included in the following narrative.
The Commander of the First Escort Fleet moved his headquarters from TAKAO, FORMOSA to MOJI in February 1945 and in April he was assigned the additional responsibility of defending the SHIMONOSEKI Straits against mine attack. In this capacity the First Escort Fleet was known as the Seventh Fleet although the same staff administered both activities.
Due to the fact that the UNITED STATES did not use mines extensively during the first years of the war, the Japanese allowed their research efforts to relax and consequently were in no way prepared for the saturation type of attack that was delivered in Japanese waters in the spring of 1945. The equipment available at SHIMONOSEKI was not only insufficient in quantity but was also improperly designed.
Frantic efforts were made to counter the mining of SHIMONOSEKI Straits which had a normal traffic of 1,250,000 tons per month, composed of 20 to 30 ships above 500 tons and 100 to 200 ships below 500 tons. An extensive system of mine watchers was immediately established by the Seventh Fleet. Watchers were stationed along coast, in adjacent hills, and in numerous fishing boats anchored in various channels. Radar, searchlights, and underwater sound equipment were employed to assist in spotting the mines. In addition a comprehensive research and counter-measure construction program was instituted and each major naval base in JAPAN was assigned a specific part of the counter-measure program.
After each mining attack it was the policy to sweep from dawn to dusk in the observed area. Since it was the practice of the U. S. Air Force to mine the eastern and western entrances alternately, the Japanese were able to anticipate the attack and concentrate all equipment in the threatened area. Captain MINAMI is of the opinion that both entrances should have been mined simultaneously, thus forcing the Japanese to divide the sweeping equipment available.
The mining of the Strait itself caused the Japanese considerable trouble because of the currents which complicated sweeping and moved the mines and because of the necessity of sweeping the entire Strait completely in order that ships could move to moorings along the beach.
When the Strait was mined, many mines were invariably recovered on the beach. On 27 May the Japanese recovered 30 such mines and it was at this time they discovered the magnetic pressure type. At times the traffic in the Straits became so jammed that it was necessary to force ships through regardless of losses. Occasionally destroyers and submarines passed through the Straits. On 25 May one light cruiser and six destroyers proceeded through the Straits although it was not considered safe. One destroyer was hit and heavily damaged. Two submarines were sunk at a later date and shortly after the war, two destroyers were sunk while en route to SASEBO.
The number of premature explosions of American mines puzzled the Japanese and they established a research section to investigate the possible causes. No definite answer was arrived at, although it was noted that the number were greatly reduced during the last weeks of the war.
Although night fighters were furnished by the Japanese Army for the defense of SHIMONOSEKI Straits, they were very ineffective. Anti-aircraft fire from escort vessels succeeded in destroying one B-29 on 27 May and one on 9 July.
Assisted by Lieutenant Commander MIBU, Masatake, who was also assigned to the Staff of the First Escort Fleet, Captain MINAMI furnished the following general information relative to mined areas outside of Japanese home waters.
Mines were laid by CHINA-BURMA-INDIA aircraft in February 1944. One small vessel was damaged and one 500 ton vessel was sunk. The above sinking was the first indication of the presence of mines since mining was performed during a bombing raid. Immediately after the sinking, the port was closed for one week. The three channels in TAKAO were easily swept with the magnetic bar and net type sweepers.
One large merchantman was damaged and beached. Number of mines were insufficient to cause serious trouble. Area between HONGKONG and HAINAN Many small ships mined and sunk. Considerable damage January and February 1945. One 10,000 ton tanker mined and heavily damaged. Shipping routes were continually changed in an effort to avoid mines.
One tanker sunk in East Strait in January 1945.
Many small ships sunk and damaged. Sweeping operations complicated by mud and river currents.
One coast defense ship and one 5,000 ton transport sunk.
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