In September 1944, the US 81st “Wildcat” Infantry Division seized the seemingly unimportant Ulithi Atoll during the Peleiu campaign. Just six months later, the Ulithi Atoll was the largest US naval anchorage outside of the continental US, including Pearl Harbor.
The Ulithi Anchorage was built by three Seabee battalions between October, 1944 and February, 1945, with the first aircraft landing on the Ulithi ten days after the Wildcats captured it. The Seabees constructed six airstrips with full maintenance facilities, an aviation tank farm, a seaplane base, and pontoon piers, that stood up to a typhoon, for dozens of ships. Whole islands of malarial ridden swamp were paved over for the facilities. A landing craft base was constructed and eleven water purification and distillation units set up around the islands with a 5000 gallon water tower. A fleet recreation center took up a large portion of the atoll and was a major project for the Seabees. By February, Ulithi could house and entertain 8000 men and 1000 officers, boasting two bandstands, a 500 seat chapel, 1200 and 1600 seat theaters, massive beverage refrigerators, and numerous baseball diamonds and sports fields. The islands were covered with “quonset huts for storage, shops, mess halls, offices, and living quarters, and building roads, supply dumps, and necessary facilities to supply water and electricity to all parts of the island”. The Seabees completed the work in just 4 1/2 months. In February and March 1945, Ulithi was the staging base for the largest amphibious operation of the Pacific War: Operation Iceberg, the Invasion of Okinawa.
On 22 March 1945, the last of the 180,000 men of the US Tenth Army were loaded on transports. The final ships bearing the US 1st, 2nd, and 6th Marine Divisions, and US Army’s 7th, 27th, 77th, and 96th Infantry Divisions departed the atoll on the 1400 ships of the US Fifth Fleet that afternoon for the trip to Okinawa. The waters around Ulithi Atoll on 22 March 1945 was the largest concentration of fighting ships the world had ever seen — before or since.
Okinawa was the last stop before the invasion of the Japanese Home Islands. The Battle for Okinawa was the second largest naval battle of the war, second only to Battle of Leyte Gulf in October. The US Navy took more casualties in it than in any other battle of the war, including Pearl Harbor. The invasion of Okinawa was second largest amphibious operation of the war, with the Invasion of Normandy just squeaking ahead. Okinawa was the largest land battle in the Pacific and had a higher casualty rate than the largest American battle of the war, the Battle of the Bulge.
Today, both Okinawa and Ulithi are mostly forgotten.