Operation Hailstone - Chuuk Lagoon

The Japanese Pearl Harbour

In 2018 I had the incredible opportunity to visit one of the worlds’ most remote, desired wreck diving destinations. A true paradise for wreck divers of all levels, but especially so for those who have a passion for deeper exploration and a love of engine rooms! I had the honour to visit and dive the wrecks of Chuuk Lagoon, Micronesia.

The History

Two mighty bases – Chuuk and Rabaul – protected Japan’s pacific empire. 74 years ago, a devastating carrier raid, Operation Hailstone, brought both of them down. Japan had been mandated the islands of Micronesia following World War 1, and had exploited the natural geography of the lagoon to create a safe haven for their war fleet that could accommodate the largest ships of the Imperial Japanese Navy. (IJN) The coral atoll surrounding Chuuk’s islands created a safe harbor whose few points of ingress the Japanese fortified with antiaircraft guns and other equipment. Hidden from world view, Chuuk had developed a reputation of nearly insurmountable strength. Chuuk was perceived to be a heavily fortified base for Japanese operations against Allied forces in New Guinea and the Solomon Islands Chuuk’s facilities included; 5 air strips, sea plane bases, a torpedo boat station, submarine repair shops, a communications centre and a radar station.

The Chuuk Lagoon

The lagoon was first built up to house the IJN’s 4th fleet, its "South Seas Force" and had since been the home-away-from-home for the Combined Fleet vessels operating in the South and Central Pacific. At anchor in the lagoon, were the Imperial Japanese Navy's battleships, aircraft carriers, cruisers, destroyers, tankers, cargo ships, tugboats, gunboats, minesweepers, landing craft, and submarines. After the outbreak of war with the United States, the 4th Fleet was put under the command of the Combined Fleet, which continued to use Chuuk as a forward operating base into 1944. With thousands of troops, and cave emplaced armament among the islands overlooking the lagoon, the "Gibraltar of the Pacific" was a threat to any allied operation in the pacific. In the autumn of 1943, following spectacular victories earlier in the war, Japan was on the defensive. It had suffered heavy aircraft and ship losses in the South Pacific, where the Allies were advancing up the Solomon Islands chain and along the coast of New Guinea, and now another Allied offensive was brewing in the Central Pacific. What the Japanese needed was time to rebuild their forces and prepare a comeback. Recognizing that it could not defend everywhere, Japan established a National Defense Zone. Territories within that area, considered essential and to be held at all costs, included the Combined Fleet base at Chuuk Atoll. However, by early 1944 Chuuk was increasingly unsustainable as a forward base of operations for the IJN and as a result, the IJN relocated Combined Fleet's forward base to Palau and had begun withdrawing fleet units from its anchorages out of Chuuk in as early as October 1943.

The Fleet

After reconnaissance flights, the Americans realised that this tiny atoll was in fact the largest Japanese military base in the entire Pacific theatre. As such, the United States started planning an attack with the main aim to destroy all the ships of the area and cripple the Japanese Imperial fleet. Once the American forces captured the Marshall Islands, they used them as a base from which to launch an early morning attack on February 17, 1944 against Chuuk Lagoon. Operation Hailstone lasted for three days. Despite the impressions of U.S. Navy leaders and the American public concerning Chuuk's projected fortifications, the base was never significantly reinforced or protected against attack. In fact, the development of Chuuk only began in hurried fashion, in late 1943, when airfields were extended, shore batteries were installed and other defensive measures taken against U.S. encroachment. Five fleet carriers and four light carriers, along with support ships and some 500 aircraft, descended on the islands in a surprise attack. Forewarned by intelligence a week before the US raid, the Japanese had withdrawn their larger warships (heavy cruisers and aircraft carriers) to Palau. But still Approximately 250 Japanese aircraft were destroyed and more than 50 ships sunk. The three carrier task groups committed to Hailstone moved into position and began launching their first fighter sweep 90 minutes before daybreak on 17 February 1944. Problematic for the Japanese was that the radar on Chuuk was not capable of detecting low-flying planes — a weakness probably known and exploited by Allied intelligence organizations. Because of these factors, U.S. carrier aircraft achieved total surprise. Though there were more than 300 Imperial Japanese Navy Air Service (IJNAS) and Imperial Japanese Army Air Service (IJAAS) planes present at Chuuk on the first day of attacks, only about half of them were operational! Due to the lack of air cover or warning, many merchant ships were caught at anchor with only the islands' anti-aircraft guns for defence against the U.S. carrier planes. Some vessels outside the lagoon already steaming towards Japan were attacked by U.S. submarines and sunk before they could make their escape. Torpedo bomber and dive bomber squadrons from the carrier air groups (CAGs) were responsible for the bulk of the damage inflicted on Japanese ground facilities. The consequences of the attack made "Chuuk lagoon" the biggest graveyard of ships in the world.

The End Result

An estimated 400 Japanese soldiers were killed in one ship alone, trapped in the cargo hold. Most of the fleet remains in exactly the same spot it was left, largely forgotten by the world until the late 1960s. Jacques Cousteau’s 1969 film Lagoon of Lost Ships explored the wreck-littered lagoon, and many of the sunken ships were then still full of bodies. As wreck divers brought attention to the site, Japan began recovery efforts, and many bodies have been removed and returned to Japan for burial. A few, however, remain. Chuuk, like so many other Japanese bases, was left to wither away without hope of resupply or reinforcement. Army forces which had arrived at the atoll before the U.S. attacks put increasing strain on available foodstuffs and medical supplies. Dwindling ammunition even limited the ability of shore batteries to fend off intermittent attacks by Allied forces. Losses at Chuuk were severe. The isolation of this whole area of operations by submarine and air attack began the effective severance of Japanese shipping lanes between empire waters and critical fuel supplies to the south. Chuuk was cut off from supplies and was reduced to near-uselessness. The garrison sat out the remainder of the war. Starvation nearly wiped out the garrison by the time Japan surrendered. Chuuk is renowned today as a tourist destination for extended range divers interested in seeing the many shipwrecks left in the lagoon, many of which were caused by the Operation Hailstone strikes. It is a "bucket list" destination for any history buff or wreck lover, a destination not to be missed. My trip was organized by Tekstreme Diving who have teemed up with Master Liveaboards to offer technical safari trips to explore the wonders of this incredible area and give you the chance to taste the history. You can find out more information in the SSI MyDiveGuide  here Operation Hailstone in Chuuk Logoon Operation Hailstone in Chuuk Logoon Operation Hailstone in Chuuk Logoon Diving in Chuuk Lagoon Artillery in Chuuk Logoon