Marines in the Mariana Islands ALINK="00FFFF" BACKGROUND="ega_color_back.gif">

Marines in the Mariana Islands





In June 1944, the U.S. Navy opened the greatest simultaneous naval expeditions ever attempted. In that month, with Great Britain bearing the greatest share in Europe, the United States mounted Operation Overlord, the invasion of France, and Operation Forager, the invasion of Saipan, Tinian and Guam in the Mariana Islands.

While Overlord was much the larger campaign, the Marianas posed challenges that were new to the Pacific theater. The island chain's distance from supply bases stretched the Navy's capability to transport and supply an invasion force. The Navy's logistical planners and fleet service force proved both innovative and successful in bringing material forward.

Once delivered to the theater of operations, men and material faced rugged terrain including cliffs, swamps and mountains honeycombed with caves. These caves offered better protection to the Japanese defenders than they had been able to construct for themselves on sites such as Tarawa.

Planners deemed the Marianas important because the Army Air Corps needed bases from which its long-range bombers could make non-stop strikes on Japan. Additionally, the Navy wanted Saipan and Guam developed as advance bases, and hoped a Marianas operation would draw out the Japanese Combined Fleet so it could be engaged in a decisive battle. (This hope was realized in the Battle of the Philippine Sea.) The idea of freeing the population of Guam from Japanese occupation (the Japanese had taken Guam, a U.S. territory, just two days after Pearl Harbor) also had great political and psychological appeal.

The Attack Force



The scope of the Marianas operation required a much larger force than any previous Central Pacific amphibious operation. Vice Admiral Richmond Kelly Turner, veteran of Guadalcanal, Tarawa and the Marshall Islands, commanded the approximately 800 ships and 162,000 men of the Marianas Joint Expeditionary Force. Turner also led the Northern Attack Force, designated for Saipan and Tinian. Rear Admiral Richard L. Conolly commanded the Southern Attack Force, designated for Guam.

Two amphibious corps had responsibility for the action on land. The V Amphibious Corps under Marine Lieutenant General Holland M. Smith was assigned to take Saipan and Tinian. This corps was made up of the 2nd and 4th Marine divisions, reinforced by the Army's 27th Infantry Division in reserve. The III Amphibious Corps under Marine Major General Roy S. Geiger consisted of the 3rd Marine Division, the First Provisional Marine Brigade and the Army's 77th Infantry Division in reserve. It was assigned to Guam.

Saipan



D-Day for Saipan, headquarters of Japan's Central Pacific Fleet, was June 15, 1944. The island's Japanese defenders numbered almost 30,000. While the Navy landed 8,000 Marines from the 2nd and 4th divisions in the first 20 minutes of the assault, Japanese shoreline defenses kept the invasion force fighting for three days to protect the beachhead.

Naval bombardment on the first day was insufficient, although it improved to the point that one Japanese officer credited it as the single greatest factor in the American victory. Four battleships, five cruisers and 39 destroyers provided on-call fire, with destroyers taking out enemy gun positions and the larger ships assigned to saturation bombardment. Gunboats, converted infantry landing craft, were especially effective against the caves because their shallow draft allowed them to move in close to shore. Illumination from Navy-launched star shells helped the Marines protect their lines at night.

Saipan's mountainous terrain made seizure of the approximately 14-mile-long by 6-mile-wide island an arduous process for the Marines and the 27th Infantry Division. Prolonged hand-to-hand combat characterized the campaign. In addition to the fierce enemy resistance and the logistical problems caused by the sheer size of the U.S. force, the mix of unfamiliar Army and Marine units made coordinating their movements difficult.

From their original beachheads on the island's southwest coast, it took the 4th Division Marines until July 9 to reach Marpi Point at Saipan's northern tip. There, the remaining defenders and a number of Japanese civilians jumped from the high cliffs rather than surrender; estimates of the total number of civilians who killed themselves on Saipan run as high as 22,000. All but a thousand of the Japanese defenders died in battle or by their own hands. U.S. casualties on Saipan were 16,612; 13,000 were Marines. Due to the difficulties on Saipan, the invasion of Guam, scheduled for June 18, was postponed until late July.

Tinian



Three miles to the south of Saipan, Tinian offered the best site in the Marianas for the extra-long runways required by the B-29 Superfortress. The island was defended by about 9,000 Japanese troops, who were well prepared to fight at the shore of the only beach suitable for an amphibious landing, Tinian (Sunharon) Harbor along the southwest coast of the island. In the hope of achieving tactical surprise, expeditionary force commander Turner decided to attempt landings on two tiny beaches at the northwest tip, where the coral cliffs were relatively low and defenses were minimal. The narrowness of the beaches made rapid movement of supplies off the beach a necessity, or the landing would quickly back up. This was accomplished with ingenuity in ship-to-shore and shore party procedures.

Tinian underwent over 40 days of preliminary naval gunfire and bombing from the air. The Army Air Corps tested napalm bombs, attempting to work out the mix of napalm powder with gasoline or oil. Shore fire-control was improved because fire-control parties spent time working out procedures on board the gunfire ships designated to support the landing.

On D-Day, July 24, the 4th Marine Division crossed the narrow channel from Saipan, making the initial foray. The 2nd Division provided a convincing diversion off the southwest coast of the island. Shore-based artillery and naval bombardment gave plentiful support to the troops, as did Saipan-based Marine and Army aircraft. Opposition to the landing was not strong, and by the time the Japanese gathered in force to counterattack, the Marines were firmly established. Several counterattacks came during the first night, in which the Japanese lost more than 1,200 men. On the second day of the invasion, the 2nd Marine Division came ashore and joined the 4th, sweeping to the south and pressing the defenders back.

By August 1, all organized resistance had ceased. The scene in the southern part of the island was a smaller-scale repetition of that on Saipan. Japanese civilians killed themselves by jumping off the cliffs, although more than 13,000 civilians were captured and put in stockades. Marine casualties included 290 killed, 1,515 wounded and 24 missing. After the island was secure, 6,050 Japanese fighting men were counted as killed, and some 500 more died in mop-up operations. The fate of the remaining Japanese force is unknown: they are presumed to have died in caves or escaped in small boats.

Guam



Terrain on Guam, which measured approximately 28 miles long by 4 to 8 miles wide, was similar to that of Saipan. There were about 19,000 fighting men on the island, who, with the five-week delay in the invasion, had the opportunity to construct formidable underwater defenses. The defenders received concentrated bombardment from American air and naval forces, including a 13-day continuous naval bombardment, the most prolonged of the war.

The invasion force's objective was to quickly take Apra Harbor on the west coast and the Orote Peninsula bounding it to the south. The 3rd Division would go in to the north of the harbor, on what were called the Asan beaches. The 1st Provisional Brigade would land about five miles to the south, just below the Orote Peninsula.

After beach reconnaissance and obstacle clearance by Navy ?frogmen? (Underwater Demolition Teams), 20,000 3rd Division Marines landed July 21 on the Asan beaches. The Japanese held the high ground overlooking the landing area, and the Marines took casualties as a result. They fought back with artillery that allowed them to hit the hidden sides of the hills, and were supported by air-spotted naval gunfire. After defeating a Japanese counterattack at dawn July 22, they began pushing up the hills surrounding the beach, clearing caves and ravines of defending Japanese. The most serious counterattack came July 25 and 26, but the Japanese were thrown back with a loss of 3,500 men. By July 28, the Marines had completed the assault phase in the north.

On July 21, the 1st Provisional Brigade faced opposition in the form of mortar and artillery fire, beginning at the reef and continuing on the beaches. Unloading did not go smoothly, and ammunition and fuel were in short supply. Despite these difficulties, the Marines reached their initial objectives by afternoon, and were reinforced by GIs from the 77th Infantry Division. The combined force pushed the enemy to Orote Point by July 25, and the U.S. flag went up on the point July 29. On Aug. 12, the last Japanese command post was overrun by units from the 77th Infantry Division, putting an end to organized resistance on Guam.

Of the 30,214 Marine participants, 1,082 were killed, 125 were missing and 4,852 were wounded. Of the 17,958 men of the 77th Infantry Division, casualties were 193 killed, 20 missing and 704 wounded. More than 17,000 Japanese were killed.



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