In June 1944, while the world watched Normandy, the United States launched the largest operation yet seen in the Pacific. An armada of 535 ships carried 127,000 troops to the Mariana Islands, about 1,500 miles south of Tokyo. In eight weeks of fighting the Americans took Saipan, destroyed Japanese carrier aviation in the Battle of the Philippine Sea, captured Tinian and liberated Guam, the American territory Japan had seized in December 1941. Japan’s prime minister fell. From airfields carved out of the islands’ coral, B-29 Superfortresses would burn Japan’s cities, and from Tinian the Enola Gay and Bockscar would fly to Hiroshima and Nagasaki.

What happened

The Marianas lay at the centre of the line Japan called its absolute national defence sphere. Saipan and Tinian had been Japanese since the First World War, home to tens of thousands of Japanese and Okinawan settlers and a thriving sugar industry; Guam had been American since 1898 until Japan took it on 10 December 1941. For the United States the islands offered something no other target did: airfields within B-29 range of Tokyo. In March 1944 the Joint Chiefs of Staff ordered the invasion, Operation Forager, for mid-June. The reasons, and the plan, are in Chapter 1.

On 15 June the 2nd and 4th Marine Divisions landed on Saipan’s southwest coast under fire from guns on the high ground, as told in Chapter 2. The landing brought out the Japanese fleet. On 19 and 20 June, in the Battle of the Philippine Sea, American fighters shot down most of the planes Admiral Ozawa sent against Task Force 58, submarines sank the carriers Taihō and Shōkaku, and a long-range strike at dusk sank Hiyō. Ashore, Marines and the Army’s 27th Infantry Division fought north through the island’s mountainous centre (Chapter 4), and on 7 July the garrison made the largest banzai charge of the war. Saipan was declared secure on 9 July, as hundreds of civilians died at the northern cliffs (Chapter 5).

Tinian, three miles south, fell in nine days to a landing on two tiny beaches the Japanese thought impossible, described in Chapter 6. On Guam, where the Chamorro people had endured two and a half years of occupation, forced labour and, in July 1944, massacres and forced marches to inland camps, the 3rd Marine Division, 1st Provisional Marine Brigade and 77th Infantry Division landed on 21 July. The island was secured on 10 August. That story is told in Chapter 7.

Within weeks Seabees and Army engineers were building the bases for the Twentieth Air Force. The first B-29 landed on Saipan on 12 October 1944, and on 24 November 111 bombers struck Tokyo. From March 1945 the fire raids led by Curtis LeMay devastated Japan’s cities, and in August the atomic bombs left from North Field on Tinian. The air war from the Marianas is in Chapter 8, and the cost and memory of the campaign in Chapter 9.

Why it matters

The Marianas campaign was one of the decisive campaigns of the Pacific war. The Battle of the Philippine Sea ended Japan’s carrier air power; the Japanese navy never again had trained aircrew to fill its carriers, which at Leyte Gulf four months later served only as decoys. The fall of Saipan breached the inner defence line, and on 18 July Prime Minister Hideki Tojo and his cabinet resigned. Many Japanese leaders came to recognize that the war could no longer be won.

The campaign also showed how the rest of the war would be fought. The defence of the caves and ridges, the gyokusai attack and the deaths of thousands of civilians on Saipan foreshadowed Iwo Jima and Okinawa and shaped American estimates of the cost of invading Japan. And the islands themselves became the base from which the United States waged the air war that, with the atomic bombs, brought Japan to surrender. For Guam, 21 July is still Liberation Day.

How to use this collection

The nine chapters follow the campaign in order. Chapter 1 covers the islands, the strategy and the plan; Chapter 2 the Saipan landings; Chapter 3 the Battle of the Philippine Sea; Chapter 4 the fighting for the centre of Saipan and the “Smith versus Smith” controversy; and Chapter 5 the gyokusai attack, the cliffs and the end on Saipan. Chapter 6 is Tinian, Chapter 7 the occupation and liberation of Guam, Chapter 8 the B-29 bases and the air war on Japan, and Chapter 9 the cost and the memorials.

The map below follows the campaign across the western Pacific; Chapters 2, 4 and 6 have a detailed map of Saipan and Tinian, and Chapter 7 a map of Guam. For the campaign before this one see Tarawa and Kwajalein; for what came after, Leyte Gulf, Iwo Jima and Okinawa. The Navajo Marines who served on Saipan and Guam have their own section, and the bombs that left Tinian are covered in the Manhattan Project collection. Times are local times as given in the sources.