Truk 1944–45

The destruction of Japan's Central Pacific bastion

Mark Lardas, Adam Tooby

• Publisher: Osprey Publishing
• Year: 2021
• Print ISBN: 9781472845856
• eBook ISBN: 9781472845863
• Edition: 1
• Topic: History
• Subtopic: Military & Maritime History
• Index: History

A fully illustrated history of how the US Navy destroyed Truk, the greatest Japanese naval and air base in the Pacific, with Operation Hailstone, and how B-29 units and the carriers of the British Pacific Fleet kept the base suppressed until VJ-Day.

In early 1944, the island base of Truk was a Japanese Pearl Harbor; a powerful naval and air base that needed to be neutralized before the Allies could fight their way any further towards Tokyo. But Truk was also the most heavily defended naval base outside the Japanese Home Islands and an Allied invasion would be costly. Long-range bombing against Truk intact would be a massacre so a plan was conceived to neutralize it through a series of massive naval raids led by the growing US carrier fleet. Operation Hailstone was one of the most famous operations ever undertaken by American carriers in the Pacific.

This book examines the rise and fall of Truk as a Japanese bastion and explains how in two huge raids, American carrier-based aircraft reduced it to irrelevance. Also covered is the little-known story of how the USAAF used the ravaged base as a live-fire training ground for its new B-29s -- whose bombing raids ensured Truk could not be reactivated by the Japanese. The pressure on Truk was kept up right through 1945 when it was also used as a target for the 509th Composite Squadron to practise dropping atomic bombs and by the British Pacific Fleet to hone its pilots' combat skills prior to the invasion of Japan.

THE CAMPAIGN

From feared bastion to the Allies’ punchbag

Japan gained Truk in 1914. In the opening months of World War I, Japan occupied German holdings in the Central Pacific, taking German-controlled islands in the region with virtually no opposition. When World War I ended, German Pacific holdings, including Truk, were confiscated and transformed into League of Nations mandates. Japan was assigned to be the mandate trustee in the formerly German-occupied islands of the Marianas, Caroline, and Marshall islands. Known as the South Seas Mandate, it was officially titled the Mandate for the German Possessions in the Pacific Ocean lying north of the Equator. It included every island in these groups, with the exception of Guam, which had been a US territory since 1898.

Twelve radar-equipped Grumman Avengers from the USS Enterprise flew the first radar-guided night attacks from a United States Navy aircraft carrier during the pre-dawn hours of February 18, 1944. They made 13 hits during the attack. (AC)

As trustee, Japan did not exercise sovereignty over these islands; it was supposed to administer them for the benefit of its inhabitants. Sovereignty was vested in the League of Nations. Truk was thus not technically part of the Japanese Empire, merely administered by Japan, “under the laws of the Mandatory as integral portions of its territory.”

In reality, though, these islands were ruled as part of the Japanese Empire. The islands were administered by the Imperial Japanese Navy between 1914 and 1919. Then the Treaty of Versailles gave sovereignty of the islands to the League of Nations, which assigned them to Japan. Japan excluded other nations from them during World War I, a policy that continued under League of Nations mandate. Truk was administered as a Japanese territory, although it transitioned from direct Navy administration to the Navy’s Civil Affairs Board in 1920 and the Ministry of Colonial Affairs in 1929.

The League of Nations mandate forbade fortifying mandate territories, or building military or naval bases in them. At Truk, during the period in which Japan was in the League of Nations and in the years immediately after withdrawing, the Japanese observed this restriction. It maintained no military garrison, while port facilities were those appropriate for supplying the civilian needs of the islands, both Japanese and native. When the Imperial Japanese Navy appeared, it used Truk as an anchorage, refueling from tankers. This was due less to Japan’s honoring the terms of its mandate than because Japan couldn’t afford to build a large fleet and militarize its overseas possessions.

Two F-7As on a training run. The F-7A was the photo-reconnaissance version of the B-24 Liberator, its bomb bay filled with cameras. F-7As were used extensively during the reduction of Truk, for pre-mission reconnaissance and post-mission bomb damage assessment. (AC)

Japan withdrew from the League of Nations in 1933. This should have ended its mandate over Truk and other Pacific islands, but the League lacked the means to expel Japan. Japan refused to leave and continued administering them. This, combined with Japan’s isolation of their islands from other nations, led the intelligence services of the Royal Navy, US Navy, and Royal Australian Navy to imagine Truk was heavily fortified and possessed significant naval and military installations.

What was indisputable was that Truk’s geographic location made it a key roadblock to an Allied advance to Tokyo. It had to be captured or neutralized before the Allied advanced beyond it. Tentatively during 1943, Allied planners considered the task of dealing with Truk. In the opening months of 1944, they executed their plan, leading to a two-phase campaign which defanged Truk’s threat.

Background: 1939–January 1944

On November 15, 1939, the Imperial Japanese Navy created the Fourth Fleet, with the mission of protecting its South Seas Mandate. War in Europe had started 75 days earlier. With Britain distracted by European events, Imperial Japan began asserting a more aggressive posture. A fleet base was necessary. Centrally located and with an outstanding anchorage, Truk was chosen as headquarters for the Fourth Fleet. A base force was created at Truk to coordinate the naval defenses of the Caroline Islands, as were base forces at Saipan in the Marianas and Kwajalein in the Marshalls to coordinate the defenses of those island groups.

Over the next 25 months, formerly sleepy Truk was transformed into Japan’s largest naval base outside the Home Islands. Existing port facilities and the seaplane base at Dublon were expanded. Ammunition bunkers, torpedo facilities, and repair and maintenance shops were erected. The seaplane base was enlarged and fuel storage capacity expanded. In November 1940, shore batteries and minefields were installed to cover the passes allowing entry into the lagoon. Antiaircraft guns were sent to protect the new installations. A supply department was established at Fefan in December 1940. A 2,500-ton floating dry dock arrived in 1941, and in November that year, a month before Japan attacked Pearl Harbor, work on an airfield began, the first of four airfields that would be built in the atoll.

For the first two decades that Japan held Truk it had no airfield, no naval facilities, and minimal port facilities. During this period, the Imperial Japanese Navy’s presence was limited to courtesy visits by small, often elderly warships, such as this pre-war visit by the gunboat Yodo. (USNHHC)

On December 8, 1941, when the Pacific War began at Truk (it was west of the International Date Line), its importance as a base exceeded its available facilities. The occupation of the Marshall Islands, Bismarck Archipelago, New Guinea, and the Solomon Islands were all coordinated from Truk in the war’s opening months. Aircraft from Truk’s still incomplete Moen No 1 airfield, with its still-primitive facilities, launched the first air raids against Rabaul and Kavieng in January 1942. Troops sent from Truk occupied New Britain and New Ireland the following month. They soon spread to the adjacent Solomons and New Guinea. Truk coordinated the occupation of Makin, and Tarawa in the Gilbert Islands in December 1941, and Nauru starting in May 1942.

By the Battle of Midway, in early June 1942, Truk was Japan’s most critical supply and administrative center in the Pacific. Ships sailing from Truk brought supplies and reinforcements to Japanese-occupied territory in an arc from Tarawa in the southeast to Lae, New Guinea, in the southwest. Aircraft were shipped to Truk, assembled, and flown on from there to forward bases. Troops from Japan also moved through Truk before being sent to garrisons guarding Japan’s outer defensive perimeter.

In 1942 and 1943, Truk was a boom town. The additional airfields and a new seaplane base neared completion as 1944 approached. Aircraft maintenance and assembly facilities went up at Truk’s airbases, to support the hundreds of aircraft passing through. The supply depot at Fefan swelled, reaching its full capacity only in December 1943.

But even at its height, Truk had only limited facilities. By 1944, its service craft consisted of 50 sampans, ten 15-ton tugs, one 600-ton tug, three 800-ton tugs, three water lighters, three fuel barges, and 17 small yard craft. Its repair facilities were also limited: they could not repair major battle damage on vessels larger than destroyers. Truk’s yards could only make temporary repairs on battle damage to larger warships, sufficient to allow them to return to Japan for permanent repairs.

These deficiencies proved a problem. In December 1941, the Fourth Fleet was a collection of destroyers, overaged light cruisers, armed merchant cruisers, minesweepers, and attack transports capable of moving a battalion-sized Special Naval Landing Force to invade Allied islands. By July 1942, Truk was home port for the Combined Fleet: Battleship Division 1, four cruiser divisions, Carrier Division 3 (with Naval Air Flotillas 1 and 2), two destroyer squadrons, and two submarine squadrons.

Japan’s Fourth Fleet was headquartered at Truk. It consisted of a small number of auxiliary cruisers and elderly light cruisers and destroyers. These included four obsolescent Kamikaze-class destroyers, like the one pictured. (AC)

The fleet’s battleships (Yamato, Mutsu, and Nagato before Musashi became operational, Yamato and Musashi thereafter), two aircraft carriers, ten to 12 heavy cruisers, and 18–24 destroyers were a significant proportion of Japan’s naval power. Permanently stationed at Truk, they strained its maintenance and supply capabilities. And they were not the only Japanese warships using Truk. Except for the slow battleships, virtually every ...

Table of contents

• Cover
• Title Page
• Table of Contents
• Introduction
• Chronology
• Attacker’s Capabilities
• Defender’s Capabilities
• Campaign Objectives
• The Campaign
• Aftermath and Analysis
• Further Reading
• eCopyright