Honolulu, Hawaii · October 29, 1943

In World War II’s Pacific Theater, sea mines—explosive underwater devices that damaged, sank, or deter­red Japa­nese war­ships, sub­marines, and mari­time com­merce—were wea­pons that had dif­ficulty gaining the same respect as guns, bombs, and tor­pe­does enjoyed in the U.S. ar­senal. Over time, how­ever, a small number of mining advo­cates in both the U.S. Navy and the U.S. Army Air Forces in­fluenced their ser­vice bosses enough to en­sure the growth of offen­sive mine-laying, equip­ment development, and combat experience.

On this date in 1943 U.S. sub­ma­rines began mining the waters off French Indo­china. The following March the U.S. Navy mounted a direct aerial mining attack on Japa­nese ship­ping on Palau Island in the West­ern Pacific, which stopped 32 Japa­nese ships from escaping Palau’s har­bor. Com­bined with bombing and strafing attacks, the opera­tion sank or damaged 36 ships.

The most suc­cess­ful mining opera­tions were those con­ducted by the Allied air forces laying aerial mine­fields. Begin­ning with a very suc­cess­ful attack on the Yan­gon River in Burma (Myan­mar) in Febru­ary 1943, B‑24 Libera­tors, PBY Cata­linas, and other avail­able bomber air­craft took part in local­ized mining opera­tions in the China Burma India (CBI) Theater and in the South­west Pacific (Philip­pines, the Dutch East Indies, Bor­neo, New Gui­nea, and the west­ern Solo­mon Islands). British and Royal Aus­tralian air forces carried out 60 per­cent of the sor­ties and the U.S. Army Air Forces and U.S. Navy carried out the balance. U.S. Adm. Thomas C. Kinkaid, who directed nearly all RAAF mining opera­tions in the CBI, wrote in July 1944 that “aerial mining opera­tions were of the order of 100 times as destruc­tive to the enemy as an equal num­ber of bombing missions against land targets.”

The U.S. mining effort against the Japa­nese Home Islands proved very suc­cess­ful, closing major ports like Hiro­shima on West­ern Honshū, the largest Home Island, for days. At best, the Japa­nese suc­ceeded in sweeping only about 50 per­cent of Amer­i­can acoustic mines (they meas­ured sound of cer­tain fre­quen­cies). Pres­sure mines, the most com­monly used against Japan near the end of the war, were even more dif­fi­cult to sweep. By war’s end, more than 25,000 U.S.-laid sea mines were still in place. Over the next 30 years, more than 500 mine­sweepers were damaged or sunk in continuing clearance efforts.

My 103-year-old father-in-law Capt. Benja­min A. Nicks of Shawnee, Kansas, recently passed away. He was priv­i­leged to serve with Maj. Gen. Curtis “Iron Ass” LeMay, head of the XXI Bomber Com­mand, out of Tinian Island in the Mari­ana Islands chain between Febru­ary 1, 1945, and August 10, 1945. Ben was a B‑29 air­craft com­man­der who, on his eighth mission with his crew of 11, was in the initial group that on March 27, 1945, kicked off Opera­tion Star­va­tion, the aerial mine-laying opera­tion whose intent was to strangle Japanese marit­ime traffic in the waters surrounding the Japanese Home Islands. In his official and personal reports of his crew’s 14‑hour round trip to Osaka Bay off the city of Kobe, situated on the main island of Honshū, Nicks wrote: “General LeMay assigned the project to the 313th Bom­bard­ment Wing and our crew was one of the 200 planes in the mis­sion. . . . We carried six 2,000‑lb mines with para­chutes attached. . . . The para­chute slowed down the 2,000‑lb mine so it wouldn’t shatter upon impact. . . . The mis­sion was flown as briefed and our mines were placed exactly where we wanted them. It was a beau­ti­ful night over Japan and the moon was so bright you could even make out objects on the land below. Our alti­tude was 5,000 feet. We had no oppo­si­tion, although we did see a couple of fighters. They never came very near. The bom­bar­dier saw two bursts of flak way up ahead of us. There were two black holes in the left wing when we landed but it [flak] was well spent when it hit us apparently.”—Submitted by C. M. “Mike” Adams

Operation Starvation: Strangling Japanese Maritime Traffic

B-29 aerial miningM26 sea mine

Left: Overseen by Maj. Gen. Curtis LeMay, Operation Star­va­tion was a joint U.S. air and naval effort. The main objec­tives of Opera­tion Star­va­tion were to pre­vent the impor­ta­tion of raw mate­rials and food into Japan, pre­vent the supply and move­ment of mili­tary forces, and disrupt shipping in Japan’s Inland Sea, the body of water that separates Honshū, Shikoku, and Kyūshū islands. Beginning on March 27, 1945, B‑29 Super­for­tresses assigned to Opera­tion Star­va­tion dropped 825 parachute-retarded influ­ence mines with mag­ne­tic and acous­tic explo­ders. The ini­tial sortie was followed up on March 30 by 1,528 more. Some models of mines had water-pressure-displace­ment explo­ders. Aerial mining proved the most effi­cient means of destroying Japa­nese shipping during the war. In terms of damage per unit of cost, it surpassed the stra­te­gic bombing and the U.S. submarine campaigns against Japan.

Right: A 1,000 lb Mk 26 sea mine being dropped by a B‑29, 1945. LeMay’s XXI Bomber Com­mand laid 12,135 mines in 26 fields on 46 sepa­rate mis­sions. The Japa­nese employed 349 vessels and 20,000 men to clear mines. Over the course of the war, aerial, sur­face, and sub­marine mine-laying sank or damaged over 2 mil­lion tons of enemy ship­ping, a volume repre­senting nearly one quarter of the pre­war strength of the Japa­nese mer­chant marine. After the war, the com­man­der of Japan’s mine-sweeping opera­tions noted that he thought the U.S. mining cam­paign could have led directly to the defeat of Japan on its own had it begun earlier.

Sea mines ready for loadingMK 25 sea mine being loaded into B-29

Left: Sea mines prepared by mine assembly personnel on Tinian Island in the Northern Marianas are ready for loading onto B‑29s.

Right: A 2000 lb MK 25 mine is loaded into a B‑29’s bomb bay. Air­craft were loaded with an average of 12,000 lb of mines con­sisting of a mixture of 2,000 lb MK 25 mines and 1,000 lb MK 26 mines. A mix of magne­tic and acous­tic actu­ating devices was used with various sensi­tivity settings, a ran­dom mix of arming delays between 1 and 30 days, and ship counts between 1 and 9.

Planning the Defeat of Japan Down to the Last Bomb, a U.S. War Department Presentation (in color)