Marines in the Mariana Islands
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
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
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.
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.
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.
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
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
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.