Invasion of Saipan Scenario Briefing:
Japan’s inner defense was sacred, to be held at all costs. In June 1944, the Allies sought a base from which to strike Japan’s industrial capacity while reducing the Japanese defense forces. The effort to pierce Hidecki Tojo’s “inner defense line” started at daybreak 15 June 1944, with the second largest seaborne invasion in history, second only to the June 6 strike across the English Channel at Normandy, France.
Japan’s garrison was formidable, with the advantage of heavily protected stores, and a familiarity with the terrain that reached back to absorbing the land following the Kaiser’s defeat in 1918. Saipan’s geology included volcanic caves, and extensive dense vegetation cover cut by numerous valleys created by streams and small rivers. It lied at the center of a roughly 1500-mile circle radius, a range that well inside the maximum range of the United States’ newest strategic bomber, the B-29. Capture of the island not only would pierce strategic defenses but also add a strategic opportunity to strike all of Japan with systematic long range bomb attacks.
Entrusted with command of the land invasion force was US Marine Corps LtG Holland M. “Howlin’ Mad” Smith, revered as the father of the US Marine Corps’ modern amphibious attack tactics. Smith commanded three divisions in his Fifth Amphibious Corps, the US Marine Corps 2nd Marine Division, veterans of the first decisive land battle won by Allied Forces on Guadalcanal in the Pacific. Also included was the newer 4th Marine Division, veterans of action on Kwajalein / Roi Namur earlier in the year. As reserve, Smith had the 27th Army Division, an original National Guard unit from New York with combat experience on Makin Atoll in 1944 and Eniwetok a few months prior to to the Saipan campaign. The land force was supported by a massive mobile fire support base from the fast battleship fleet and the largest assembly of aircraft carriers in TF 58. The land invasion was not only designed to gain a lodgement within strategic bombing range of any place on Japan’s mainland, but also to entice the remaining units of the Combined Fleet, still formidable though seriously hurt since Midway, into a decisive sea battle.
Facing the combined US Army – Marine Corps task group was Japan’s 43rd Infantry Division, augmented with the 47th Independent Mixed Brigade, late of land battles in China under the command of LtG Yoshitsugo Saito. At the time of the invasion, he was acting head of Japan’s 31st Army, charged with defending Central Pacific defensive positions centered on the Marianas Islands with Saipan as the Marianas’ key defensive position. The Japanese had proven themselves dedicated vicious opponents of the Allies, carrying out General Hideki Tōjō’s defensive war of attrition against the assembled allied forces.
Following days of airstrikes and shore bombardment, Allied forces appeared on the horizon early in the morning 15 June, 1944, obviously intent on engaging Saito’s forces.