Who won the Battle of Saipan?
The United States won. The 2nd and 4th Marine Divisions and the Army's 27th Infantry Division landed on 15 June 1944, and Saipan was declared secured on 9 July. Almost the entire Japanese garrison of about 30,000 died, and American killed, wounded and missing came to between about 14,000 and 16,600.1
Saipan was not a coral speck like Tarawa. It was a mountainous island of sugar fields and towns, governed by Japan since World War I under a League of Nations mandate, home to thousands of Japanese settlers and about 1,250 to 1,270 nautical miles from Tokyo. Taking it meant breaking what the Army historian Philip Crowl called the inner line of fortifications Japan had built to defend its homeland. For the wider story, see our guide to the Pacific War, the military history of Japan and the military history of the United States.2
Why did the United States invade Saipan?
The main reason was the B-29. The Army Air Forces' new long-range bomber was due to raid Japan from bases in China, but General Henry Arnold doubted that the Chinese could hold those airfields once the raids began, and he argued for bases in the Marianas, which he thought the Japanese could not retake. Admiral Ernest King had long wanted the Marianas for the Navy. In March 1944 the Joint Chiefs of Staff ordered Admiral Chester Nimitz to seize the southern Marianas, Saipan, Tinian and Guam, with 15 June as the target date.3
Seizing Saipan also promised a fight with the Japanese fleet, which American planners expected to sail out to defend the islands. The operation, code-named Forager, was the largest amphibious operation yet in the Pacific: Admiral Raymond Spruance commanded the whole force, Vice Admiral Richmond Turner the amphibious ships, and Lieutenant General Holland Smith the troops ashore.4
How did Japan plan to defend Saipan?
For Tokyo, the Marianas were not a distant outpost. Japan's national archives describe them as part of the “absolute national defense sphere,” the area that had to be held at all costs if Japan was to win the war. On 14 June, the day before the landing, Vice Admiral Chuichi Nagumo, the commander of the Pearl Harbor strike force in 1941 and now head of the Central Pacific Area Fleet on Saipan, concluded, as Hoffman quotes him, that the Marianas were “the first line of defense of the homeland.”5
The garrison had been rushed in during the spring of 1944, and American submarines sank many of the ships carrying its men and its building materials. Crowl counts about 45,000 army troops sent to the Marianas from January to early June, of whom at least 12,000 were aboard torpedoed ships and about 3,600 died; survivors often came ashore without their weapons. The 43rd Division arrived only weeks before the invasion. Its commander, Lieutenant General Yoshitsugu Saito, held tactical command on the island because the 31st Army's commander, Lieutenant General Hideyoshi Obata, was away in the Palau Islands when the Americans landed.6
Japanese doctrine was to destroy the enemy at the water's edge. A Saipan defense plan quoted by both Crowl and Hoffman expected the landing force to be smashed by fire before it reached the beach and by counterattacks, at night if need be, once it was ashore. The defenses were unfinished: submarines had sunk the cement, steel and barbed wire, and on 31 May the 31st Army's chief of staff complained that without materials his soldiers could only “sit around with their arms folded.” Crowl adds a cultural reason: Japanese commanders preferred to attack rather than wait in prepared positions. American intelligence had expected 15,000 to 18,000 defenders; there were roughly twice that many.7
What happened when the Marines landed on 15 June?
After two days of naval bombardment, Turner gave the order to land the landing force at 0542 on 15 June. Between 0843 and 0907 about 8,000 Marines of the 2nd and 4th Marine Divisions came ashore in hundreds of amphibian tractors on the beaches around Charan Kanoa, on the island's southwest coast, while the 27th Infantry Division waited offshore in reserve.8
The Japanese had registered their guns on the reef, using flags as aiming marks, and their artillery and mortars on the high ground inland hit every wave. Hoffman counts more than 2,000 American casualties on the first day; the 2nd Marine Division alone reported about 1,575 by nightfall, according to Crowl. Still, by dark both divisions were ashore with most of their reserves and artillery.9
That night Saito did what doctrine told him to do and counterattacked. On the 4th Marine Division's front, Japanese soldiers advanced behind a crowd of civilians, and the Marines held their fire until almost too late. The main blow fell on the 6th Marines at the north end of the beachhead, where tanks led the attack. Over the next two nights the attacks, including a large tank and infantry assault on the night of 16 to 17 June, were broken up by Marine fire and naval guns.10
How did the Battle of the Philippine Sea decide Saipan?
The Japanese fleet did come out, as both sides expected. On 19 and 20 June the carriers of Task Force 58 met Japan's carrier fleet several hundred miles west of Saipan in the Battle of the Philippine Sea, fought mostly in the air. The Naval History and Heritage Command writes that by the evening of 20 June American aircraft had broken the back of Japanese naval aviation; Japan's national archives record the loss of three carriers and a large number of planes, and the forced retreat of the fleet.11
For the garrison on Saipan, the battle ended any hope of relief from the sea. Captain Mitsuo Fuchida, the Combined Fleet's air staff officer, said after the war, as Hoffman quotes him, that Japan had used up practically all of its air strength in it. Meanwhile, ashore, the Army's 165th Infantry had taken Aslito airfield on 18 June, and the Marines swung north across the island toward Mount Tapotchau.12
What happened at Mount Tapotchau and in Death Valley?
The center of Saipan is a tangle of ridges, cliffs and caves under Mount Tapotchau, the island's highest peak, from which Japanese observers could see almost every American move. When the 27th Infantry Division was sent into the line between the two Marine divisions on 23 June, its soldiers attacked up a valley east of the mountain under fire from the slopes on both sides. The Americans named the places Death Valley and Purple Heart Ridge.13
Progress there was slow, and Holland Smith, a Marine, blamed the Army division and its commander, Major General Ralph Smith. With the approval of Spruance and Turner, he relieved Ralph Smith of command on 24 June. The “Smith versus Smith” affair set off a long quarrel between the services. The Army's own official history, quoted also by Chapin, later concluded that Holland Smith had good reason to be disappointed with the division on 23 and 24 June, despite several extenuating circumstances, but doubted that relieving Ralph Smith was wise: it did nothing to speed the capture of Death Valley.14
On 25 June the 8th Marines worked their way onto the summit of Mount Tapotchau, and on 30 June the 27th Division at last broke through Death Valley and Purple Heart Ridge. Saito's men, short of food, water and ammunition, fell back toward the north.15
How did the Japanese fall back to the north of the island?
Saito had given up his plan of driving the Americans into the sea and fought a withdrawal, line by line. On 2 July the 2nd Marines moved into Garapan, the island's administrative town, by then a field of ruins, and cleared it over the next two days. To the south, a cut-off Japanese force on Nafutan Point broke out through the American lines on the night of 26 to 27 June and was destroyed.16
By early July Saito's headquarters had moved into a cave in a valley the Americans later called Paradise Valley. A Japanese officer who was with him, quoted by Crowl, described the general as weak from days without food or sleep and wounded by a shell fragment. On 4 July the 2nd Marine Division was pinched out of the line, and the 27th Division and 4th Marine Division pushed on toward the island's northern tip.17
What was the banzai charge on Saipan?
On the morning of 6 July Saito issued his last order. “Whether we attack or whether we stay where we are, there is only death,” it read, and Saito pledged to advance “with those who remain to deliver still another blow to the American Devils, and leave my bones on Saipan.” Saito did not lead the attack: too weak to do so, he took his own life, and Admiral Nagumo died with him; the National Park Service notes that the Japanese commanders and thousands of others chose suicide rather than surrender. The Americans called such an attack a banzai charge, after the battle cry; the Japanese term was gyokusai, which Japan's national archives explain as an “honorable death” and the National Park Service translates loosely as the breaking of jewels, an image of death in the face of defeat.18
Before dawn on 7 July the attackers, drawn from almost every unit left on the island and some armed only with bayonets tied to poles, poured south along the coastal plain. They struck the 1st and 2nd Battalions of the 105th Infantry, found a gap between them and overran both positions in close fighting; the two battalions lost 406 killed and 512 wounded. Their commander, Lieutenant Colonel William O'Brien, fought with a pistol in each hand and then with a machine gun until he was killed, and Thomas A. Baker of Company A, badly wounded, asked to be left behind with a loaded pistol. Both received the Medal of Honor.19
The wave reached a battalion of Marine artillery behind the Army line before it was stopped. Afterward the Americans counted 4,311 Japanese dead in the area, some of them killed earlier by shellfire. How many men took part is not known: Crowl thought about 3,000 was as good an estimate as any, and the National Park Service puts the Japanese dead at 3,000 to 4,000. It was the largest such attack of the war.20
What happened to the civilians at Marpi Point?
Saipan was full of civilians. The National Park Service counts about 20,000 Japanese settlers and about 4,000 Chamorros, the islands' native people; PBS puts the civilian population close to 30,000, including Korean laborers and Carolinian islanders, and notes that most of the Japanese had come from Okinawa. Many hid in caves with the soldiers, and American patrols spent days coaxing them out with interpreters and loudspeakers.21
As the Americans reached the northern tip, hundreds of civilians took their own lives. On 9 July and the days that followed, families jumped from the cliffs at Marpi Point, at the places now known as Banzai Cliff and Suicide Cliff, or waded into the sea; Crowl writes that the water below was at times so thick with bodies that small craft could not steer around them. PBS estimates that close to 1,000 civilians died at Marpi Point alone.22
Why they did it is still debated. Many had been told that Americans would torture and kill them, which both the National Park Service and PBS name as a cause. Marine witnesses quoted by Chapin saw soldiers shoot civilians who tried to surrender and throw grenades into a crowd of families, and the Park Service records an unknown number of cases in which soldiers killed civilians or forced them to die. Hoffman adds a caution: when intelligence officers of the landing force questioned some 150 Japanese and Chamorro civilians on this point, none said they had been threatened or used as shields, though Hoffman adds that those who might have said otherwise were probably dead.23
How many people died in the Battle of Saipan?
On the American side, Crowl estimates that 3,674 Army and 10,437 Marine Corps personnel were killed, wounded or missing, 14,111 in all, about a fifth of the combat troops, as at Tarawa and Peleliu. Chapin, counting differently, gives 3,225 killed, 13,061 wounded and 326 missing; the National Park Service rounds the figures to nearly 3,000 killed and more than 10,000 wounded, and EBSCO's reference entry gives 3,471 dead and 13,160 wounded.24
The Japanese garrison was almost wiped out. Chapin counts 23,811 known Japanese dead and only 736 prisoners, 438 of them Koreans; the National Park Service gives 921 prisoners, EBSCO about 28,500 Japanese killed, and the Park Service's Pacific exhibit more than 28,000 dead. Civilian deaths are the least certain figure. The Park Service reasons that about 26,000 civilians were on the island and about 18,000 were interned, which suggests about 8,000 dead in the fighting and the suicides; the historian John Toland, cited in The Asia-Pacific Journal, put the toll at 22,000 Japanese civilians.25
Who won the Battle of Saipan, and why did it matter?
The United States won, and the victory reached far beyond the island. On 18 July 1944, nine days after Saipan was declared secured, Prime Minister Hideki Tojo and his whole cabinet resigned. Senior Japanese officers said afterward that the war had been lost there: “Our war was lost with the loss of Saipan,” Vice Admiral Shigeyoshi Miwa told American interviewers, a remark quoted by both Hoffman and Chapin.26
Saipan also gave the Americans the base they had come for. Aslito airfield, rebuilt, was ready for B-29s in October, Hoffman records, and on 24 November 1944 Saipan-based B-29s raided Tokyo, the start of the bombing campaign against Japan's cities. Tinian and Guam were taken within weeks, the first by the same two Marine divisions.27
The battle taught the Japanese army a lesson it applied for the rest of the war. Hoffman notes, and Crowl agrees for Iwo Jima and Okinawa, that the defenders of Peleliu, Iwo Jima and Okinawa gave up defense at the beaches for positions in depth, in caves and hills. Some of Saipan's defenders held out long after the battle: Captain Sakae Oba led a small band in the hills until he surrendered on 1 December 1945.28
Compare the other island battles of the Central Pacific drive, from Tarawa in 1943 to the naval battle at Leyte Gulf that followed in October 1944, and see where Saipan stands among the greatest battles of the Pacific War and the commanders of the Pacific War.
Where is Saipan, and where was the battle fought?
Saipan lies in the Mariana Islands of the western Pacific, with Tinian three miles to the south and Guam about a hundred miles beyond. The Marines landed on the southwest coast near Charan Kanoa, fought north through the central mountains past Mount Tapotchau and Garapan, and ended at Marpi Point on the northern tip. Today the National Park Service's American Memorial Park on Saipan commemorates the battle, and memorials stand at Banzai Cliff.29
Test what you remember in the World War II battles quiz, or read about the day of the landing in 15 June in history and the banzai charge in 7 July in history.
.jpg){kind=link}