From The Marine Corps History Division…
The 24 July – 1 August 1944 campaign for the assault and capture of the Mariana Islands played a vital role in the final defeat of Japan. Planners deemed the islands of Guam, Saipan, and Tinian of critical importance because the Army Air Corps needed bases from which its long-range bombers could make non-stop strikes on Japan. Additionally, the Navy wanted the islands developed as advance bases, and hoped that a Marianas operation would draw out the Japanese Combined Fleet so that it could be engaged in a decisive battle.
After the capture of Saipan in early July 1944, the next step in this campaign was Tinian, whose relatively flat terrain was ideally suited for the construction of airfields for the new American B-29 bombers. Vice Admiral Richmond Kelley Turner, USN, commanded the approximately 800 ships and 162,000 men of the Marianas Joint Expeditionary Force. Turner also led the Northern Attack Force, designated specifically for Saipan and Tinian. The task of taking Tinian fell to the 2d and 4th Marine Divisions, under the overall command of Major General Harry Schmidt, USMC, Commander, V Amphibious Corps.
Tinian underwent over 40 days of preliminary naval gunfire and bombing from the air. Shore fire control was improved from previous campaigns as fire-control parties worked out procedures on board the gunfire ships designated to support the landings. Photo reconnaissance flights and captured enemy documents on Saipan gave a clear picture of the topography of Tinian, and for the first time napalm was used extensively and proved successful in burning off ground cover.
On D-Day, 24 July, the 4th Marine Division led the assault, while the 2d Marine Division provided a convincing diversion off the southwest coast of the island. Shore-based artillery and naval bombardment provided plentiful support to the assaulting Marines, and opposition to the landing was not strong. Subsequent Japanese counterattacks were repulsed by the well-entrenched Marines. On the second day of the invasion, the 2d Marine Division came ashore to join their 4th Division brethren in sweeping to the south and pressing the Japanese defenders back.
By 1 August, after nine days of fighting in a battle often termed “the perfect amphibious operation” of World War II, General Schmidt declared the island of Tinian secured. The combination of surprise, heavy pre-assault bombardment and effective logistical support was responsible for Tinian’s recapture with a much lower casualty rate than had been experienced in previous amphibious landings. Almost a year after its re-capture, Tinian played a final, decisive role in the defeat of the Japanese when a B-29 bomber, the “Enola Gay” left Point Ushi Airstrip on Tinian, carrying the atomic bomb that would be dropped on Hiroshima.