The recapture of Guam and the broader Mariana and Palau Islands campaign resulted in the destruction of much of Japan's naval air power and allowed the United States to establish large airbases from which it could bomb the Japanese home islands with its new strategic bomber, the Boeing B-29 Superfortress.

The United States plan for the invasion of the Marianas, Operation Forager, called for heavy preliminary bombardment, first by carrier aircraft and U.S. Army Air Forces bombers based in the Marshall Islands to the east, then once air superiority was gained, close bombardment by battleships, cruisers, and destroyers.

[2]: 22  Saipan, Tinian, and Guam were chosen as the targets because of their size and suitability as bases for supporting the next stage of operations toward the Philippines, Taiwan, and the Ryukyu Islands.

The seaport at Apra Harbor was suitable for the largest ships; and air bases for Boeing B-29 Superfortresses could be built from which to bomb Japan.

[2]: 25 U.S. naval and air bombardments lasted from 11 to 13 June 1944, involving 216 carrier aircraft and land-based B-24 bombers from the Marshall Islands.

[2]: 42 United States US Fifth Fleet Admiral Raymond A. Spruance, USN Southern Attack Force (Task Force 53) Vice Admiral Richard L. Conolly, USN Expeditionary Troops Lieutenant General Holland M. Smith, USMC Approx.

48,200 officers and enlisted III Marine Amphibious Corps Major General Roy S. Geiger, USMC

In addition, 13 aircraft carriers participated in the air raid, and 4,283 bombs (weighing a total of 1,310 tons) were dropped from 18 to 20 July, the day before the landings.

However, artillery pieces entrenched in dense forests, caves, trenches and locations four kilometers or more from the coast were able to escape destruction and became a source of heavy Japanese resistance.

The men stationed in the two beachheads were pinned down by heavy Japanese fire, making initial progress inland quite slow.

The 1st Provisional Brigade blocked off the Orote Peninsula on 25 July, and that same night Takashina counterattacked, coordinated with a similar attack against the 3rd Division to the north.

[2]: 73–74  The 1st Provisional Brigade formed up on the left flank of the 3rd Marine Division on 7 August because of the widening front and continued casualties, in an effort to prevent the Japanese from slipping through gaps in the line.

[2]: 81  The next day, Obata committed ritual suicide at his headquarters on Mount Mataguac after he had sent a farewell message to Japan.