Battle of Guam

In late 1943, Admiral Chester W. Nimitz proposed a plan to capture the Mariana Islands. Capturing Guam, Saipan and Tinian would give the United States airfields that were within the range of the new B-29 bombers. This would allow America to bomb the Japanese home islands. The code name of the Marianas operation was "Forager."

Preparing for Invasion

For two weeks leading up to the invasion, the United States bombed the island. Battleships hurled 836 sixteen-inch rounds and 5,422 fourteen-inch shells. Cruisers fired 3,862 eight-inch and 2,430 six-inch rounds. Destroyers fired 16,214 five-inch shells.

While the bombardment battered the coast, the American Underwater Demolition Teams (UDTs) blew gaps in the rugged coral reefs surrounding the island. Destroying obstacles and mines, this created a route to shore for landing vehicles.

Ashore in the North

The Battle of Guam began on the morning of July 21, 1944, W Day for Guam. While a simultaneous attack launched five miles south at Hågat, the Third Marine Division, led by Major General Allen Turnage, landed on Assan (Asan) Beach.

Under the protection of heavy artillery from gunboats, the Marines were brought to shore in waves of armored Landing Vehicles and DUKWs. They landed on the beach in four groups and advanced to capture the cliffs before the Japanese could recover from the bombardment.

In three days, the Third Marine Division seized Assan and Adelup Point, captured Chorito Cliff and Bundschu Ridge, and secured the northern beachhead.

The Southern Beaches

Five miles to the south, the First Provisional Marine Brigade under the command of Brigadier General Lemuel Shepherd landed at Hågat (Agat) Beach. The area was strategically chosen to help secure the Orote Peninsula to the north—home to a strategic airfield and the entrance to Apra Harbor.

In their way were heavy Japanese fortifications. A well-hidden concrete blockhouse at the tip of Ga’an Point, missed by reconnaissance planes before the battle, remained intact. It housed a 74mm gun and a 37mm gun, which fired on the first wave of Marines as their landing vehicles reached the shore. Seventy-five Marines were killed before the blockhouse was overrun.

The 305th Infantry Regiment of the U.S. Army’s 77th Infantry Division followed the Marines ashore. Due to a shortage of LVTs, the soldiers, carrying their weapons, ammunition, and equipment, were dumped in chest-high water. They had to wade hundreds of yards to shore. The rest of the 77th Infantry, commanded by Major General Andrew Bruce, came ashore on July 22-23.

For the next several days, U.S. troops advanced during the day, then fended off Japanese counterattacks at night. Despite fierce resistance and a banzai attack on the night of July 21-22, U.S. troops captured Mount Alifan and secured the beachhead by July 24.

Attack on Fonte

While American forces had secured the beachheads at Assan and Hågat by July 24, 1944, the fight for Guam was far from over. The beachheads were narrow, isolated strips of land surrounded by well-fortified hills and mountains still controlled by the Japanese. To join their position, the U.S. needed to secure the line of peaks stretching from Adelup Point in the east to Måkpo Point in the west. This would connect the two beachheads and allow American troops access to the rest of the island. However, they first needed to capture the Japanese stronghold on Fonte Plateau, which overlooked Assan Beach.

The Third Marine Division launched their attack on Fonte on the morning of July 25. By the end of the day, most of the battalions had reached the critical Mt. Tenjo Road, which crossed the high ground framing the beachheads.

As the Americans launched their assault, Lieutenant General Takeshi Takashina, commander of the Japanese forces on Guam, planned a major counterattack. He mustered more than 5,000 soldiers, the majority of his remaining forces in southwest Guam, on Fonte Plateau. His plan was to surge down the slopes surrounding the Assan beachhead and push the Americans to the edge of the water.

At 3:00 am, Japanese troops poured down the slopes from Fonte Plateau in a forward moving, last-ditch effort, to give their all in a banzai attack. Shouting, “Wake up American and die!” the Japanese charged towards the American tanks, artillery, and ammunition dumps. The Japanese launched seven consecutive waves of counterattacks before dawn on July 26. While they bent, the Third Marines did not break. Not only did the Japanese fail to break the American line, but they also suffered tremendous casualties. 3,200 of the best remaining Japanese soldiers on Guam died during the banzai.

After spending July 26 reorganizing and recovering from the night’s attack, the Marines renewed their assault on Fonte Plateau on July 27. By July 29, Fonte was in American hands. To the west, the 9th Marines made contact with a company of the 307th Infantry Regiment at Mt. Tenjo, securing the two beachheads.

Orote

While the Third Marine Division worked on securing the high ground overlooking the beachheads, the First Provisional Marine Brigade attacked Orote Peninsula, the strip of land jutting out into the ocean between the two beachheads. Home of the Orote airfield and an Imperial Japanese Army garrison, the peninsula was well-defended. The Japanese had constructed an elaborate interlocking system of pillboxes, strongpoints, and trenches.

Starting on July 25, the Marines fought their way through the swamps and thick jungle, forcing the Japanese defenders to the tip of the peninsula. On the afternoon of July 25, Japanese Commander Asaichi Tamai tried to evacuate his troops by barge across Apra Harbor in broad daylight. U.S. artillery and air strikes sank the barges.

His next plan was a frontal assault of the First Provisional Marine Brigade’s lines. Shortly before the banzai attack on the Third Marine Division began, the Orote defenders stormed out of the mangrove swamp at the Americans. Despite fierce fighting all night long, the Japanese troops were not able to break the American lines.

The First Provisional Marine Brigade continued their advance through the dense mangroves and swamps the following morning. They captured the former Marine Barracks and the village of Sumai on July 28. The following morning, after a furious barrage of artillery and airstrikes, the Marines captured the Orote airfield, and the peninsula was declared secure. Phase 1 of the liberation of Guam was complete.

The Final Battle for Guam

After Takashina's death on July 28, General Hideyoshi Obata assumed command of the remaining 6000 Japanese soldiers on Guam. He withdrew his forces to the north of Guam and established his final defensive position in the Mount Mataguac-Mount Santa Rosa area.

General Roy Geiger, commander of the American forces on Guam, allowed his tired troops to rest for a few days. They started marching north on July 31. By August 6, the defense line that Obata had set across Guam had been shattered and overrun.

The final battle for Guam began at noon on August 7. The 77th Infantry Division captured Yigu (Yigo) on August 7. On August 8, they surrounded and secured the mountain, but only 600 bodies were found after the two-day fight. Significant numbers of Japanese soldiers were still hiding in Guam’s jungles. The Third and Ninth Marines defeated many of the remaining soldiers over the following days.

On August 10, 1944, patrols from the 77th Infantry Division approached Obata’s command post at Mt. Mataguac. A full-scale battle ensued. Obata knew the end was near and radioed his last messages to Japan: "I will engage the enemy in the last battle with the remaining strength at Mount Mataguac tomorrow, the 11th." The next morning, U.S. soldiers assaulted the hill, then descended into the depression where they sealed the caves with several 400-pound blocks of TNT. The explosion killed the remaining defenders, including Obata.

Guam was officially declared secure at 11:31 on August 10.

1,769 Americans died during the Battle of Guam. 23,303 Japanese defenders died between July and September on Guam. Less than 1,500 surrendered. Admiral Nimitz established his forward CinCPac-CinCPOA headquarters in Guam and directed the rest of the war in the Pacific from the island.