Figure 1.--Here a Japanese torpedo plane or bomber attacking the U.S. carrier task force assaulting the Japanese base at Truk Lagoon has been shot down. It may be a Yokosuka D4Y Suisei which the Allies called Judy. A HBC reader believes that it is Nakajima B5N Kate, the standard Japanese carrier torpedo bomber. When the Imperial Navy withdrew after the Guadalcanal campaign, some carrier aircraft and pilots were reassigned to Rabaul and Truk and operated there. The effectiveness of these planes were compromsed by the introduction of improved American fighters, especially the Grumman F6F Hellcat. The photograph captures the last seconds before the plane which hs been hit and trailing smoke impacts the water. You can see the rear gunner trying to see what is happening, but is not bailing out. Click on the image for a fuller discussion.

The Japanese considered Truk Lagoon in the Caroline Islands to be their Gibraltar in the Central Pacific. It was the most powerful base in the Pacific War with the exception of Pearl Harbor. They considered it to be impregnable. Truk was a magnificent anchorage surrounded by coral reefs which made attack difficult. Truk had been a German colony. The League of Nations after World War I awarded Truck to Japan. As part of the award there were restrictions on fortifying the island. Japan ignored those limitations and during the 1930s illgally fortified it. It was the Imperial Japanese Navy's Fourth Fleet base (November 1939). The powerful Combined Japanese Navy Fleet was based at Truk (July 1942-to February 1944). This included carriers and legendary battleships such as the Yamato. About 37,000 Japanese were based at Truk, overwealming the small local population. Ships based at Truk played an important role in the Japanese offensive that began at Pearl Harbor and swept through the Pacific. The base was defended by five airfieds and seaplane bases. Some were began as civilian facilities, but easily converted for military opertions. Torpedo nets and air fields protected the fleet and made it a very difficult target for the U.S. Navy, especially in 1942 before the arrival of the Hellcat that gave Ameruican carriers an effectve fighter that could compete with the Zero. The base at first did not have substantial repair facilities or fortifications and other defences to oppose an American landing force. As the military situation changed in the Pacific, the Japanese Army was committed in force to defend Truk (January 1944). The Army set about building coastal defence (pillboxes, bunkers, and caves) and augmenting anti-air craft instalions in preparation for an expected amphibious invasion. The Americans did strike in force, but with air attacks. Carrier strike forces began hitting Truk (February 1944). American submarine also made it increasingly difficult for the Japanese to supply Truk. The Navy air assault began with Operation Hailstone (February 17 and 18, 1944). This was followed up with additional attacks (April 30 and May 1, 1944). These attacks were followed with repeat raids by B-24 and B-29 bombers for several months. A British Aircraft Carrier group hit Truk (June 1945). Long before that the pounding by American air attacks forced the Imperial Navy to withdraw the fleet. While the Japanese effectively used Truk as an advanced base in 1941-42, they were because of the air attacks unable to use it to resist the U.S. Navy offensive in the Central Pacific. More than 4,000 Japanese Navy and Army personnel were killed and wounded and over 50 ships (mostly merchant vessels) were sunk in Truk Lagoon and a similar number sunk outside the Lagoon. The number of war ships sunk was limited because the Imperial Fleet withdrew its major assetts just before the American air strikes begun. The air strikes destroyed about 400 aircraft. And by 1944 Japan had no way of replacing that number of planes. The United States never actually invaded Truk, but the withdrawl of the Combined Fleet and the destruction of the planes based there effectively neutalized the island as an important base. Operations in the Carolines did not end here. Th two countries fought a bloody, sencless engagement for the Palaus--especially Pelilu. But for some reason, the Japanese abandoned Ulithi with its magbificent natural harbor. It woyld be the Pacific Fleet's most important forward supply base for operations in the Western opavific.

World War I

Japan at the time of World war I had a naval treaty with Britain. Officials determined that they could benefit by joining Britain in the War. Truk had been a German colony. The Japanese seized German colonies in the Centrl Pacific. One of them was Truk and the other Caroline Islands. The League of Nations after the War awarded Truck to Japan as a Mandated Territiry. As part of the award there were restrictions on fortifying the island. Japan ignored those limitations and during the 1930s illegally fortified Truk which wa developed into a major bastion and fleet anchorage.it.

Japanese Bastion

The Japanese considered Truk Lagoon in the Caroline Islands to be their Gibraltar in the Central Pacific. It was the most powerful base in the Pacific War with the exception of Pearl Harbor. They considered it to be impregnable.

Truk Atol

Truk was a magnificent anchorage surrounded by coral reefs which made attack difficult.

Fleet Anchorage

It was the Imperial Japanese Navy's Fourth Fleet base (November 1939). The powerful Combined Japanese Navy Fleet was based at Truk (July 1942-to February 1944). This included carriers and legendary battleships such as the Yamato. Ships based at Truk played an important role in the Japanese offensive that began at Pearl Harbor and swept through the Pacific.

Garrison

About 37,000 Japanese were based at Truk, overwealming the small local population. The base was defended by five airfieds and seaplane bases. Some were began as civilian facilities, but easily converted for military opertions. Torpedo nets and air fields protected the fleet and made it a very difficult target for the U.S. Navy, especially in 1942 before the arrival of the Hellcat that gave Ameruican carriers an effectve fighter that could compete with the Zero. The base at first did not have substantial repair facilities or fortifications and other defences to oppose an American landing force. As the military situation changed in the Pacific, the Japanese Army was committed in force to defend Truk (January 1944). The Army set about building coastal defence (pillboxes, bunkers, and caves) and augmenting anti-air craft instalions in preparation for an expected amphibious invasion.

Imperial Navy Withdraws the Fleet

Before that the American air assaults began pounding Truk, the Imperial Navy withdraw the fleet.

American Carrier Assault: Operation Hailstone (February 17-18, 1944)

The Americans did strike in force, but with air attacks. Admiral Marc Mitscher commanding a massive carrier group. American industry had transformed the ballance of pwer in the Pacific. Mitscher had 9 carriers with 589 planes supported by 45 surface ships and 10 submarines. American submarines had made it increasingly difficult for the Japanese to supply Truk. The Navy air assault began with Operation Hailstone (February 17 and 18, 1944). More than 4,000 Japanese Navy and Army personnel were killed and wounded and over 50 ships (mostly merchant vessels) were sunk in Truk Lagoon and a similar number sunk outside the Lagoon. The number of war ships sunk was limited because the Imperial Fleet withdrew its major assetts just before the American air strikes begun. The air strikes destroyed about 400 aircraft, most of the Truk air component.

Eniwetok (February 18)

The United States did not invade Truk. The large, well equipped Japanese garrison thre would have made that a bloody affair. An airbase, however, was needed in the Carolies. A day after the carrier assault on Truk bgan, American Marines stormed Eniwetok. The destruction of the Japanese air craft on Truk mean that the Japanese garrison on Eniwetok would receive no air support.

Second American Carrier Strike (April 30 and May 1, 1944)

The Japanese were shocked that their Pacific Gibraltar had been devestated in only 2 days by an American carrier assault. The Imperial Navy declined to intervene. The Japanese Army, however, flew its remaining air component at Rabaul to Truk where it could be used to impede the American Central Pacific campaign. When american reconisance aircraft spoted the Japanese build up on Truk, a second carrier strike is ordered. The carrir strikes (April 30 and May 1, 1944) destoy most of the planes on Truk. And by 1944 Japan had no way of replacing that number of planes or getting them and the fuel needed to operate them to Truk. This essentially ended Truk's role as an important Japanese base.

Subsequent Bombing Raids

These attacks were followed with repeat raids by B-24 and B-29 bombers for several months. These were made asier because the carrier strikes had destroyed the Japanese air defense capability. Most of the raids were conducted by B-24s. The B-29s were limited to 2 or 3 training bombing missions against Japanese submarine pens and due to various reasons were mostly ineffective at knocking out those pens, but some limited damage was done which did hampern their use for resupply efforts to the base which was now cut off from any regular supply missions.

Impact

While the Japanese effectively used Truk as an advanced base in 1941-42, they were because of the air attacks unable to use it to resist the U.S. Navy offensive in the Central Pacific. The United States never actually invaded Truk, but the withdrawl of the Combined Fleet and the destruction of the planes based there effectively neutalized the island as an important base. Thus Truk would not impede the next American offensive in the Central Pacific, the critial assault on the Marianas.

Supply

The American offensive in the Central Pacific meant that the Japanese could no longer supply Truk. Merchant vessels could not reach Truk. The Japanese used submarines to supply some of its Pacific outposts. Truk was not, however, small outpost. The Japanese brought in a substantial army force to defend Truk, expecting an American invasion. As a result the food shortage after Truk was cut off became desperate. When Japan surrendered (August 1945), the Truk garrison was near starvation.

Ulithi Atoll (September 1944)

Ulithi Atoll, also known as the Mackenzie Islands is a coral atoll in the Yap Islands, the western part of the Carolines. There are some 40 islets withn a total land area of 1.75 square miles (4.5 square km). It is located about 190 km east of Yap. The atoll’s inhabitants are probably of mixed Polynesian and Micronesian origins and speak Ulithian, an Austronesian language. It is one of the greatest natural harbors in the world. Ulithi appears to have been first sighted by Portuguese navigators (1526). No other record exists until Spanish Jesuit missionaries led by Juan Antonio Cantova landed (1731). Along with rest of the Carolines, the Germans purchased it from the Spanish and Japan seized it during World War I. After the War, the League of Nations awarded a mandate to the Japanese. The Japanese made little use of Ulithi, but did site a seaplane base there. They had a radio and weather station on Ulithi and the Imperial Navy had occasionally used the lagoon as an anchorage. The United States used it very differently. The Pacific Fleet at first avoided landinfs in The Carolines. What they wanted was the Marianas to the north wherevair bases could be used to bomb the Japanese Home Islands. Japanese garrisons in the Carlines, luke Truk, were neutralized rather than invaded, avoiding costly landings. As the Americans moved west toward the Philippines, it became obvious that a forward supply base was needed. Naval planners bgan asessing Ulithi. The Japanese who has established garison all over the Central Pacific, somehow failed to perceive the vast strategic importance of Ulithi. The atoll with its magnificent harbor was precisely what the pacific Fleet needed for its operations in the Western Pacific. A regiment of the US Army's 81st Division landed unopposed (September 23, 1944). They simply walked ashore and took possession of the Atoll. It was a gift of unimaginable value, a starategic prize that would play an important role in the final phase of the Pacific War. Tragically, the Americans and Japnese in the same month would fight an extended pitched battle for Pelilu in the Palaus, another chain in the Carolines of virtually no value. A battalion of Seabees followed. While a magificent natural harbor, it was totally undeveloped. The survey ship USS Sumner) assessed the lagoon and concluded it was capable of accomodating an stonishing 700 vessels. This was more than Pearl Harbor and then Majuro after the seizure of the Marshalls could handle. The Pacific Fleet rapidly turned it into the major supply base for major operations in the last year of the War (the Philippines and Okinawa). This was done with little publicity, but the Japanese eventually found out what they had conceded to the Americans without a fight. Japanese midgit subnarines attacked islamd in the harbor, but despite their success had no real impact on the supply operatiins there. After the War, Ulithi was used as a military radio outpost.

The Palaus (September 1944)

Palau became important in World War II because of its location off the Philippines. After the American victory in the Marianas (June-July 1944), it became clear that the next American offensive would be to retake the Philippines. The United States in preparation for the invasion of the Philippines wanted a secure logistical base. American forces attacked Peleliu (September 1944). What was anticipated to be a quick campaign turned into horendous, protracted battle (September-November 1944). The Japanese having anticipated an American invasion, heavily garrisoned the Islands and dug into the rugged terraine. The fighting continued for more than 2 months (November 1944). Many military historians judge the invasion to have been unecessary and a costly mistake. More than 2,000 Americans died in the fighting. The 10,000 Japanese garrison on Peleliu fought to the death. After the War, Japanese civilians were repatriated.

British Carrier Assault

A British Aircraft Carrier group hit Truk (June 1945).

Created: 1:11 AM 4/12/2008
Last updated: 4:54 AM 10/24/2015