Operation Hailstone and the Battle of Eniwetok: February 17–22, 1944

On February 17, 1944, the United States launched one of the most devastating and strategically decisive naval‑air assaults of the Pacific War. Known as Operation Hailstone, the two‑day strike targeted the Japanese stronghold at Truk Lagoon-today called Chuuk-long regarded as the "Gibraltar of the Pacific." The attack coincided with the opening moves of the Battle of Eniwetok Atoll, a complementary operation aimed at securing the Marshall Islands and tightening the noose around Japan's Central Pacific defenses. Together, these actions marked a turning point in the U.S. island‑hopping campaign and showcased the growing dominance of American carrier power.

The Strategic Setting

By early 1944, the U.S. Navy's Central Pacific drive-led by Admiral Chester W. Nimitz, Commander in Chief of the Pacific Ocean Areas-was accelerating. The capture of the Gilbert Islands in late 1943 and the ongoing assault on the Marshalls placed American forces within striking distance of Truk, the main forward base of the Imperial Japanese Navy (IJN). Truk served as a major anchorage, repair facility, and staging point for Japanese warships, aircraft, and supply convoys.

To support the next major objective-the invasion of Eniwetok Atoll-Nimitz ordered a massive pre‑emptive strike to neutralize Truk's ability to interfere. The task fell to Vice Admiral Marc A. Mitscher, commander of Task Force 58, the fast‑carrier striking arm of the U.S. Fifth Fleet under Admiral Raymond A. Spruance.

Launching Operation Hailstone

Before dawn on February 17, Mitscher's carriers-Enterprise, Yorktown, Essex, Intrepid, Bunker Hill, and Cowpens-launched waves of fighters, dive‑bombers, and torpedo planes against Truk. The Japanese, aware of American advances, had already withdrawn their major capital ships, but the base still held a large number of merchant vessels, auxiliary craft, aircraft, and shore installations.

American aviators quickly established air superiority. Carrier fighters swept the skies, destroying dozens of Japanese aircraft on the ground and in the air. Dive‑bombers and torpedo planes followed, striking ships anchored in the lagoon and hammering fuel depots, airfields, barracks, and ammunition stores.

Surface ships under Rear Admiral Jesse B. Oldendorf and submarines positioned outside the lagoon joined the attack, intercepting fleeing vessels and tightening the trap.

The Destruction of Truk

Over two days, Operation Hailstone inflicted catastrophic losses:

- More than 40 Japanese ships sunk, including transports, tankers, and auxiliaries

- Over 250 Japanese aircraft destroyed

- Critical infrastructure crippled, including fuel tanks, repair facilities, and communications centers

The scale of destruction rivaled the later carrier strikes at the Philippine Sea and Leyte Gulf. Truk, once the pride of the Japanese defensive perimeter, was effectively neutralized as a major naval base for the remainder of the war.

For the U.S., the operation demonstrated the overwhelming striking power of fast carriers and validated the Navy's emerging doctrine of mobile, long‑range offensive operations.

The Battle of Eniwetok Begins

While Truk burned, American forces moved simultaneously against Eniwetok Atoll, located roughly 600 miles to the northeast. The operation was commanded by Major General Holland M. "Howlin' Mad" Smith, the fiery Marine Corps leader overseeing amphibious operations in the Central Pacific. Naval support came from Rear Admiral Harry W. Hill, who directed the landing forces.

The assault began on February 17 with the capture of Engebi Island, defended by a garrison of Japanese troops under Lieutenant Colonel Toshio Yano. After intense bombardment, the 22nd Marine Regiment stormed ashore, securing the island within a day despite fierce resistance.

Securing the Atoll

The next objective was Enewetak Island, the atoll's namesake and administrative center. On February 18, the 106th Infantry Regiment of the U.S. Army landed under heavy fire. Japanese defenders, commanded by Lieutenant Colonel Hashida Masahiro, fought tenaciously from fortified positions, but American forces gradually pushed inland. By February 21, the island was secured.

The final and most difficult target was Parry Island, heavily fortified with bunkers, trenches, and artillery. On February 22, after a massive naval and air bombardment, the 22nd Marines launched their assault. Fighting was brutal and close‑quarters, but by nightfall the island was in American hands.

With Parry secured, the Battle of Eniwetok Atoll officially ended in a decisive American victory.

Commanders Who Shaped the Operation

Several key leaders played central roles in the success of both operations:

United States

- Admiral Chester W. Nimitz – Overall Pacific theater commander

- Admiral Raymond A. Spruance – Commander, Fifth Fleet

- Vice Admiral Marc A. Mitscher – Commander, Task Force 58 (carrier strike force)

- Rear Admiral Jesse B. Oldendorf – Surface bombardment commander at Truk

- Rear Admiral Harry W. Hill – Commander, Eniwetok amphibious forces

- Major General Holland M. Smith – Commander, V Amphibious Corps

- Colonel John T. Walker – Commander, 22nd Marine Regiment

Japan

- Vice Admiral Masami Kobayashi – Commander, Fourth Fleet (responsible for Truk)

- Lieutenant Colonel Toshio Yano – Commander, Engebi garrison

- Lieutenant Colonel Hashida Masahiro – Commander, Enewetak defenses

A Turning Point in the Pacific

Operation Hailstone and the Battle of Eniwetok together marked a dramatic shift in the Pacific War. Truk's destruction eliminated Japan's most important forward base, while the capture of Eniwetok provided the U.S. with a vital airfield and staging area for the upcoming assault on the Marianas.

In just six days-from February 17 to 22, 1944-the United States demonstrated the full maturity of its carrier‑based warfare, amphibious coordination, and strategic momentum. The road to Saipan, Guam, and ultimately the Philippines now lay open.