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June 15, 1944 - Invasion of Saipan

As the world focused on the beaches of Normandy in June 1944, forces in the Central Pacific stripped the Japanese of a critical zone of defense and took another step closer to the Japanese homeland.

U.S. reinforcements wade ashore from LSTs off Saipan

U.S. reinforcements wade ashore from LSTs off Saipan. Source: National Archives

After the relative ease of the Marshall operations, Army and Marine Corps leaders believed they had conquered the technical details of amphibious landing operations. Armed with battle-tested equipment and battle-hardened troops, they collectively believed they were ready to tackle the final element of the strategy laid out in the 1943 Cairo Conference – the seizure of Guam and the Japanese Marianas – five months ahead of schedule.

The Marianas were originally a Spanish possession that the Germans purchased in 1899. The Japanese used the distraction of World War I to seize the islands along with the Marshalls and Palaus. After the war, the League of Nations formally granted the islands to Japan, with the exception of Guam which became an American territory and housed a small naval garrison consisting of 153 Marines and 271 sailors. Hours after the Pearl Harbor attacks, Japanese forces rectified this, quickly overrunning the small garrison.

27th Infantry Division SSI

27th Infantry Division SSI

Unlike the coral islands in the Gilberts and Marshalls, the Marianas, the northernmost islands in Micronesia, are a chain of fifteen volcanic islands. The 10 northern islands in the chain possessed little military value, but three of the southern islands – Saipan, Tinian and Guam -- were centrally located in the Pacific, and placed virtually every remaining Japanese territory - the Philippines, the Ryukus and the Home Islands – within range of American heavy bombers.

The landings on Saipan and Tinian fell to V Amphibious Corps, commanded by Marine Lt Gen Holland M. "Howlin' Mad" Smith, with three divisions: 2nd Marine Division, commanded by Maj Gen Thomas Watson; 4th Marine Division, commanded by Maj Gen Harry Schmidt; and 27th Infantry Division, commanded by Maj Gen Ralph Smith. Holland Smith had overseen the planning and training for the operations in the Gilberts and Marshalls, but this marked the first time that he would actually command the divisions under him in combat. Irascible and sometimes quick to judgment, he would spark controversy later in the campaign when he summarily relieved the 27th Infantry Division commander.

True to their doctrine, the Japanese defenders sought to stop the Americans at the waterline, although in a new twist, the Japanese commander positioned artillery in the hills beyond the assault beaches and staged tanks and infantry reserves for immediate counterattack. American naval gunfire and air support neutralized some fo the Japanese beach defenses but many of the assault troops faced still opposition as they landed, and an immediate counterattack by Japanese armor on the night of June 15th threatened parts of the new beached before it was overcome. Once the Americans punched through the beachhead, Japanese defenses became disjointed, if often fanatic. The 27th Infantry Division, in corps reserve during the assault, came ashore beginning on D+1, took over responsibility for clearing the southern part of the island before assuming positions alongside the Marines for the final push northward.

In addition to fanatical Japanese defenders, perhaps the most formidable obstacle on the island turned out to be the terrain. The cane fields, marshes, and mountainous topography slowed down dismounted troops and canalized vehicles onto the island's few, poorly constructed roads, forcing them into preplanned killed zones for Japanese defenders. Further slowing down the American advance was the presence of 30,000 civilians, something that had not been a factor in previous operations. It would take twenty five days for the three divisions to secure the island and a further month to mop up the remaining resistance. As the battle ended, on the night of July 6th, the remnants of the Japanese garrison launched a final desperate banzai attack, finally repulsed after it had overrun much of the Army 105th Infantry, inflicting over a thousand casualties. Within a few days, the island was declared secure.

Two events marred the victory. The first was Holland Smith's relief of Ralph Smith. Doubtful of the leadership of the 27th Infantry Division's commander as result of the earlier Gilberts campaign, and possessing a fiery temper, "Howlin' Mad" Smith had grown impatient with the division's slow movement in the rough terrain in the center of the island. Worn down by days of bloody combat, the soldiers confronted stiff resistance in the valleys and crags of Mount Tapotchau, opening gaps between the Army division and the two adjacent Marine divisions on the flanks. Without apparent warning and to many - soldier and Marine alike - perhaps too hastily, the corps commander relieved MG Ralph Smith. The ensuing controversy would sour what otherwise had been a solid military victory.

The second was even more horrific. Hundreds of civilians fled north, ahead of the American advance and sought refuge in the caves on Marpi Point at the north end of the island. Upon discovering them, the Marines gave bullhorns to the interpreters and civilians who had already surrendered and they begged their fellow countrymen to come out. However, Japanese soldiers holed up in caves shot those trying to escape. Astoundingly, many more - men, women and children - rushed out of the caves and flung themselves off the 800-foot high cliffs rather than surrender to the Americans. Still others borrowed grenades from Japanese soldiers to blow up themselves and their families. Hundreds died that day, as the Americans looked on helplessly. One Marine said of the carnage, "It makes one wonder at just how good the propaganda the Japanese had been telling the people [about the Americans]." The sight haunted even the most hardened veteran and provided a glimpse at just how far the Japanese people would go to avoid the shame of defeat.

The capture of Saipan, and adjacent Tinian a month later, set the stage for the final phases of the Pacific War, and sounded the initial death knell for the Japanese. B-29 bombers based in the Marianas would soon pound targets in Japan, while forces destined for later battles would stage through the islands. The inner defenses of the Japanese Empire had been breached.

CMH Related Publications

  • The War Against Japan
  • Western Pacific by Charles R. Anderson
  • Campaign in the Marianas, by Philip A. Crowl

Additional Resources

Saipan Medal of Honor Recipients


Stars & Stripes