World War Two, Pacific
It is often said that the Japanese navy attacked warships while the US submarines attacked merchant ships.
Pure myth. The first Japanese submarine attack was sinking of an unarmed steam schooner, Cynthia Olson simultaneously with the sneak attack on Pearl Harbor. As part of that attack, 20 Japanese submarines surrounded Pearl Harbor then moved to the West Coast to attack shipping. The reason we hear much of the German U-Boat is that they were good -- five U-boats sank 23 ships off the Atlantic coast in the first month of Operation Drumbeat without loss. Twenty Japanese I-boats in the Eastern Pacific sank only six US ships in the same amount of time with a loss of three.
The priority of all submarines is first capital warships, then down a list that is almost meaningless because a sub will simply attack the biggest target found. Warships are faster and harder to attack. The Japanese were slow
to adopt merchant convoys, meaning that many slow freighters were available targets. The US convoyed from the beginning with an escort of cruisers and destroyers. Troop convoys were escorted by a carrier -- U.S. convoys were difficult to attack. Submarines were used in fleet operations by both sides, usually as defensive lines. Several notable Japanese submarine attacks were made as part of sea battles. Yorktown, Wasp, and Juneau come to mind. In general, Japanese submarines, while always a threat, were ineffectual.
The US fleet submarine was designed to cruise to Japan from advanced bases. The Japanese had two types of submarines. Shorter range coastal defense subs, the RO-boats. And very large subs intended to reach and patrol the American coast, the I-boats. About half of the early boats carried a seaplane for scouting. Most of the others had tie-downs to carry a mini-submarine. Beginning in 1942 many Japanese submarines were stripped for use as supply ships to garrisons on isolated islands. In 1943-44 some I-boats were sent to the safer Indian Ocean to prey on lone merchantmen. The German U-boats was smaller, intended to blockade England and when the larger war started, could reach the East Coast and Caribbean only when refueled at sea.
The bulk of the US submarine fleet was stationed at Cavite in the Philippines. While the
surface portion of the Asiatic Fleet had been dispersed on the "war warning", the subs were concentrated and able to sortie with the start of the war. They were sent to observe with attack as a secondary goal. The torpedo warehouse was destroyed creating a shortage of torpedoes. Skipper were cautioned to conserve torpedoes
and to be careful to come back to report.
Air attacks on the naval yard began immediately and the three sub tenders, Canopus (AS-9), Holland (AS-3), and; Otus (AS-20) (under conversion) were sent south.
Lets sum up their effectiveness of the US submarines by noting
that 27 boats sank two enemy ships that month. There were too many problems to be able to sort out what
was wrong. It took two years.
Dud torpedoes. See torpedoes,
Ran too deep
Magnetic detonators unreliable, premature and delayed explosions.
Contact detonator failed at higher speeds.
Depth sensors in wrong place.
Loss of technicians as POWs
Japanese submarine T95M1 oxygen torpedo : 21", 900 lb warhead, 5 miles at 49 kt
American submarine Mk 14 steam torpedo : 21", 500 lb warhead, 2-1/4 m at 46 kt
The steam torpedo left a trail of bubbles pointing to the launching submarine.
As the Japanese sweep through the East Indies, the submarine force did retreat after retreat --
Cavite/Manila to Mariveles/Corregador to Dravo in the southmost Philippines, to Surabaya on the far side of Java to Darwin in the north of Australia to finally to Freemantle/Perth in the far south west corner in March.
New submarine construction assigned to Atlantic.
MacArthur insisted that supplies be brought to Corregador by submarine and key people evacuated. Reduced the number of subs for attack patrols. But subs were ineffective anyway.
January . Three ships were sunk and lost two subs while the Japanese took the Philippines, Rabaul, Borneo, Celebes.
February . The enemy reached the far end of the East Indies, Timor, from which air attacks were launched on Darwin,
sinking ships, destroying air defenses, and causing the final retreat of the submarines. The prize of Java was taken and the outpost islands in Marshalls and Gilberts. Japan controled all of Central and North pacific west of the Date Line. Two enemy ships were sunk by the remaining 26 subs.
March . U.S. subs retreat to Perth-Freemantle. Allies defeated in surface battle around Java Sea. Japanese start down Solomons to isolate Australia. Another two enemy ships were sunk.
April . Six S-boats were sent from the Atlantic to Brisbane in eastern Australia on the Java Sea. Two Japanese fleets attack shipping and warships in Bay of Bengal, sink carrier, 3 cruisers, force British fleet
across Indian Ocean to Africa. Bataan surrenders. Burma abandoned. Doolittle Raids Tokyo.
May . Battle of Coral Sea. Corregidor falls. The old "S" boats had more mechanical problems than target success.
June . Battle of Midway. All available subs called to form picket lines. Submarne Nautilus fired on damaged Kaga but no torpedoes explode, in fact, one broke apart on impact and was used as a life raft by Japanese sailors. Two Japanese heavy cruisers, Mogami and Mikuma sighted periscope of Tambor (SS-198) causing the ships to collide, one was
eventually sunk by carrier air.
July . Start of exchange of old "S" boats from Freemantle with new boats from Pearl Harbor.
Blockade of Truk; many sightings, no successes. Torpedo tests in Albany, Australia, finally get attention for torpedo failures. Both sub commands remove 11 feet from depth setting.
August . Tuluga and Guadalcanal occupied. Aug 8 near Bougainville SS-38 sinks Meiyo Maru,S-44 patroling off Kavieng and heavy cruiser Kako was put under, the first major combatant ship sunk by U.S. submarines.
September . Saratoga damaged by torpedo. Two weeks later I-19 successfully damages Wasp, North Carolina and O'Brien with one spread. Wasp is abandoned, O'Brien later sinks.
October . Bougainville, central Solomons. U.S. has enough subs to begin experiments with Wolf Packs
November . U.S. Central Pacific advance begins -- Makin, Tarawa in the Gilbert Islands
December . Magnet explored deactivated. Subs in last quarter average sinking one ship per each of 89 war patrols.
1941-42-43 text was lost to a software failure with an equally dumb failure to "backup" along the way. These are now largely recreated, but more to do.
1941. Sub fleet was at Cavite, PI. Loss of torpedoes caused shortage. Failure of boats to connect.
1942. Withdrawal to Australia. Torpedo shortage continues, had to carry mines. Torpedo failures -- a sub would risk all on an approach and then the torpedoes failed, again and again. Unsuccessful skippers removed. Japanese and Atlantic experiences.
1943. Changes made, new boats arrive, aggressive young captains, torpedoes fixed, start to see improvements. Advanced refueling bases shorten travel time.
The year 1944 was the year of the submarine -- about two warships or merchantmen were sunk each day. By the end of the year Japan had half the shipping she started the year with. There were 140 fleet submarines : wartime production :
Gato Class 72, 1942-43, 1,525 ton, 6 for+4aft tubes, 1- 4", SS-212 to SS-284, 19 lost
The USN made over 500 war patrols firing over six thousand torpedoes. Both the steam torpedo and of the new, quiet, electric torpedoes were debugged, production problems solved, and the speed of the electric had been increased to about 40 knots. Beginning in mid-1944, boats going on patrol carried 75% electric torpedoes and 25% steam. The code breakers were tracking every major enemy warship and convoy. Priority for attack had been shifted to tankers, because, with the supply of oil shut off, Japan would be immobilized.
Balao Class 121, 1943-44, 1,526 ton, 6 for+4aft tubes, 1- 4", SS-285 to SS-416, 10 lost.
IJN 'B' Class 29, 1940-42, 2,500 ton, 6 forward tubes, 1- 5.5" or 1 Glen seaplane, all but one lost.
The submarines now had advanced refitting bases which shortened the long, unproductive travel times from Pearl Harbor or Australia and could spend more time on station. allow quick return for reloading and continuing the attack. With the Marianas secure, the B-29s could pound Japanese industry to rubble -- bombing operations began in November. Oil determined Japan's strategic and tactical operations. A full blockade would strangle Japan. Germany had twice nearly brought England to her knees with submarine blockade -- now the American submarines held this over Japan. How U.S. planners could overlook this is not known. but a different path was chosen.
We have often heard that the invasion of of Pelui in September had not been necessary and could have been by-passed and the only reason it was done was because it was in the plan and nobody wanted to disrupt the shipping and troops prepared for that action. When Halsey made a softening up raid on the Palaus and central Philippines, he found that the defenses were weak and he easily destroyed a thousand planes on the ground. He recommended by-passing southern Philippines and leaping directly to Leyte. This was done in October moving the timetable up by two months. We have seen that both could have been completely by-passed. Continuing with the invasion of Palaus and Philippines caused delay in ending the war by six months, cost tens of thousands of US casualties, and drew the Pacific fleet of both aircraft carriers and submarines from the Japanese home islands to a lengthy war in the Philippines. The only purpose served was to keep MacArthur with a major part in the war. The General pleaded a U.S. promise "to return" and FDR approved going ahead with the Philippines as part of the Allied plan, even thought the competition for landing craft delayed European operations.
The next step was to have been Formosa. That delay was canceled. Ground fighting in the Philippines was tough and continued till the surrender, while American Naval efforts in the Central Pacific moved to Iwo Jima in Feb and then directly to Okinawa, by-passing China, in April as preparation to attack the home islands in Nov'45. This date might have been moved up had troops and shipping not been needed in the Philippines.
You ask, what about the Japanese troops and ships in the Philippine area? Answer, what could they to do? Certainly not attack in any sort of land-taking advance. That fleet would have had to sail over the Philippine Sea to Okinawa to attack the US fleet and the Japanese would have been annihilated there instead of at Leyte Gulf where the enemy had an advantage of being close to their fuel and had cover among the islands.
When the carrier fleet was released from the Philippines after the new year, they attacked the home islands from central, south, to north destroying aircraft and warships. The next step in the Central Pacific plan was to take the Bonins (Iwo Jima, started in February) as an advanced base for the Air Force in the Marianas (Siapan, Guam and Tinian). And then moved directly to Okinawa in April-June in preparation for the invasion of the Japanese mainland.
The submarine fleet was relegated to lifeguard service for naval air attacks in and around the Philippines and Japan and then to lifeguard B-29s on the Japan run. Japan surrendered in August.
When the numbers were added up after the surrender and using Japanese records, U.S. submarines had sunk 1,314 enemy vessels of 5.3 millions tons including a battleship, eight carriers, eleven cruisers and innumerable destroyers and escort ships. The U.S. submarine service had about 50,000 men in all capacities or 1.6% of the total Navy and accounted for 55% of Japan's maritime losses. U.S. losses had been 52 boats from all causes, 45 fleet boats. About 16,000 submariners made war patrols ; 375 officers and 3,131 men died, or 22%.
About this page: Submarines - World War II, the Pacific War, key events.
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Last updated on December 7, 2011.
Key reference: ,Silent Victory by Clay Blair, Jr. 1975, two volumes, 1,057 pages.
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