TRUCK LAGOON

Operation Hailstone: The Destruction of Truk Lagoon

Operation Hailstone, launched on February 17-18, 1944, was one of the most devastating aerial and naval assaults of World War II. The attack on Truk Lagoon, a key Japanese naval stronghold in Micronesia, was often seen as the “revenge for Pearl Harbor”, but in reality, it was the result of two years of escalating battles between the U.S. and Japan. To fully understand what led to this massive assault, we need to examine the key battles that shaped the Pacific War between December 7, 1941, and February 1944.

From Pearl Harbor to Truk Lagoon: The Road to Operation Hailstone

Pearl Harbor – December 7, 1941
The war in the Pacific began when Japan launched a surprise attack on Pearl Harbor, Hawaii. The assault crippled the U.S. Pacific Fleet, sinking battleships like the USS Arizona and forcing the United States into World War II. While Japan initially gained the upper hand, the U.S. quickly reorganized and launched counteroffensives.

The Doolittle Raid – April 18, 1942
The first significant American retaliation came in April 1942 with the Doolittle Raid. Led by Lieutenant Colonel James Doolittle, 16 B-25 bombers were launched from the aircraft carrier USS Hornet to bomb Tokyo and other Japanese cities. Though the raid caused minimal damage, it shocked Japan and proved that the U.S. could strike the Japanese mainland. This forced Japan to divert resources for homeland defense, weakening its frontlines.

Battle of the Coral Sea – May 4-8, 1942
The Battle of the Coral Sea was the first naval battle in history where aircraft carriers engaged without ships ever seeing each other. U.S. and Australian forces fought to prevent Japan from invading Port Moresby, Papua New Guinea. While the U.S. lost the aircraft carrier USS Lexington, the battle stopped Japanese expansion southward, marking the first major strategic victory for the Allies.

Battle of Midway – June 4-7, 1942
Midway was the turning point of the Pacific War. The Imperial Japanese Navy (IJN) launched an attack to capture Midway Atoll, but American codebreakers had deciphered their plans. The U.S. ambushed the Japanese fleet, sinking four aircraft carriers (Akagi, Kaga, Soryu, and Hiryu). This crippled Japan’s carrier force and put them on the defensive for the rest of the war.

Guadalcanal Campaign – August 7, 1942 – February 9, 1943
Guadalcanal was the first major land offensive by the Allies. The six-month battle in the Solomon Islands saw relentless fighting between U.S. Marines and the Japanese Army. Control of Henderson Field, an airstrip on the island, was crucial for dominance in the region. The victory at Guadalcanal marked Japan’s first major land defeat and shifted the momentum in favor of the Allies.

Island-Hopping and Central Pacific Battles (1943-1944)
Following Guadalcanal, the U.S. implemented an “island-hopping” strategy, bypassing heavily defended islands and attacking weaker points. Key battles leading up to Operation Hailstone included:
• Gilbert Islands Campaign (November 1943): The U.S. captured Tarawa and Makin Atolls in fierce battles.
• Marshall Islands Campaign (January-February 1944): The U.S. seized Kwajalein and Eniwetok, pushing closer to the Japanese stronghold at Truk Lagoon.

Operation Hailstone – February 17-18, 1944
Truk Lagoon, often called Japan’s Pearl Harbor, was the main forward base for the Imperial Japanese Navy in the Pacific. It housed multiple airfields, battleships, aircraft carriers, and supply depots. However, by early 1944, many of Japan’s capital ships had withdrawn to safer waters, leaving mostly supply ships, transports, and some warships.
The Attack
The U.S. Fifth Fleet, led by Vice Admiral Marc Mitscher, launched a two-day assault with aircraft carriers, battleships, and submarines:
• 500+ American aircraft bombed and torpedoed the fleet.
• Over 50 Japanese ships were sunk, including cruisers, destroyers, tankers, and transport vessels.
• More than 250 Japanese aircraft were destroyed.
• Thousands of Japanese sailors and airmen perished.
After the attack, Truk was no longer a major Japanese stronghold and was effectively neutralized.

Diving Truk Lagoon – The Ghost Fleet of the Pacific

Truk Lagoon is now one of the greatest wreck diving destinations in the world, with over 60 sunken warships and aircraft forming an underwater museum.
Understanding the “MARU” Shipwrecks
Many of the wrecks in Truk Lagoon are “Maru” vessels—a term used for Japanese merchant and transport ships.

• What does “Maru” mean?
The word “Maru” (丸) translates to “circle” in Japanese. It was historically used for merchant ships to symbolize safety, wholeness, and good fortune in their journeys.
• Why were transport ships called “Maru”?
Unlike warships, Maru vessels were mainly cargo, troop, and supply transports. They were essential in Japan’s military logistics. Many of these ships were later modified to carry troops, weapons, and aircraft parts, making them prime targets for U.S. forces.

Notable Wrecks in Truk Lagoon
1. Fujikawa Maru – A former aircraft transport, now famous for its intact Zero fighter planes in the cargo holds.
2. Shinkoku Maru – A massive oil tanker, now covered in coral and marine life.
3. Heian Maru – A converted passenger liner, later used as a submarine tender.
4. San Francisco Maru – Known as the “Million Dollar Wreck”, with tanks, trucks, and munitions still visible in the holds.
5. Hoki Maru – A cargo ship carrying bulldozers and construction equipment, now resting at 50 meters deep.
6. Rio De Janeiro Maru – A luxury passenger liner turned into an Imperial Japanese Navy transport ship.
7. Kensho Maru – Fantastic wreck with the cleanest and most organised engine room in history.
These wrecks are perfectly preserved time capsules, offering divers historic artifacts, wartime relics, and an eerie glimpse into the past.

Conclusion: Truk Lagoon – A Legacy of War and Peace

Operation Hailstone was a devastating blow to Japan’s naval power, effectively wiping out its stronghold in Micronesia. Today, Truk Lagoon stands as a hauntingly beautiful dive site, where wrecks from one of history’s most significant battles lay frozen in time.
For wreck diving enthusiasts and history buffs alike, exploring Truk Lagoon is a once-in-a-lifetime experience, where every dive reveals ghostly reminders of World War II’s fierce battles.
Join our expeditions to Truk Lagoon and explore the legendary Ghost Fleet beneath the Pacific!