Two months before the election, then-candidate Donald J. Trump said he would increase the size of the Marine Corps by expanding its current total of twenty-three battalions by building “a Marine Corps based on 36 battalions.” To give an idea of just how many Marines it takes to conduct a forced beach assault, in June the Marines were part of the initial invasion force of the South Pacific island of Saipan in which more than thirty battalions of Marines were needed. But the amount of naval, air, and Army ground troops it also took to take that island was even more staggering. And more vicious and bloody than can be imagined.

Japan had been on the winning Allied side during the Great War and, as part of the final settlement, had been awarded all the islands and atolls north of the equator that had previously belonged to Germany. One of these island chains was the Marianas. Part of the agreement stipulated that Japan could not militarize the islands. In 1935, however, Tokyo withdrew from the League of Nations and began building up naval bases and air strips, and garrisoning army and marine troops. The island of Saipan was especially important to Japan as a logistics hub designed to protect the Japanese mainland as far forward as possible. For nearly the same reason, it was a prime target for U.S. forces.

By February 1944 U.S. forces had captured the Marshall Islands. It was clear that the Marianas would be the next objective. Realizing the threat to their empire if the islands continued to fall to the Americans, the Japanese High Command began to rapidly reinforce Saipan. In May 1944 Japan dispatched its Forty-Third Infantry Division to reinforce the island’s defense. For security purposes, the transport ships were split into two convoys. The first arrived without incident. The second group of seven transport ships was persistently harassed by U.S. submarines: five of the seven ships were sunk before reaching Saipan. At the time of the invasion there were approximately thirty thousand Japanese troops defending the island.

Prior to the beach landings, American Naval Task Force 58 was directed to attack and destroy Japanese aircraft and naval vessels in the vicinity of Saipan that might interdict the landing forces. This powerful armada consisted of seven aircraft carries, eight light carriers, seven fast battleships, three heavy cruisers, ten light cruisers, and a whopping fifty-two destroyers. Prior to the attack, Japan was estimated to have had around 250 combat aircraft. In less than ten days the combined American air power had virtually destroyed Japan’s air ability: an estimated 215 enemy planes had been destroyed or knocked out of action, while U.S. losses were an amazing twelve. The Japanese defenders were feeling very vulnerable and isolated, as they now had neither air cover nor naval support. It was about to get much worse for them.

Now it was time for the American big guns to open up on the beach fortifications from the sea, and to bombard them from the air. Pounding the Japanese fortifications were seven battleships (of the Missouri class), eleven cruisers, twenty-six destroyers and a smattering of other vessels. Included in the attack were the California, Pennsylvania, Maryland and Tennessee—all of which had survived the Japanese attack on Pearl Harbor.

The enemy beach fighting positions, gun emplacements, and other facilities that could attack the beach were pounded, as well as airfields and other targets inland. The U.S. Army’s Center for Military History wrote the detailed description of the battle of Saipan in its Campaign in the Marianas. Despite the withering fire, according to the book’s authors, the Japanese authorities were not terribly upset by the bombardment nor did it cause undue harm to them.

Intercepted Japanese communications to the mainland recorded that the United States “did not carry out large scale shelling and bombing against the positions on the landing beach just prior to landing. When they came to the landing,” the report continued, “even though we received fierce bombing and shelling, our basic positions were completely sound.” The beach landings for the assault troops, however, were rather more terrifying.

Shortly after 7 a.m. on June 15, thirty-four Marine landing ships (known as LSTs) weighed anchor a half mile offshore and began disgorging their assault boats and other craft. In all 719 such assault craft carried the Marine and Army battalions to shore. Thirty minutes before the landings were to take place, hundreds of carrier planes and offshore firing batteries opened fire again on the beach. The purpose of these attacks, according to the Army’s history, had the “primary aim of demoralizing the enemy rather than knocking out particular installations.”

Similar to the better-known landings at Normandy in France in 1944, the beaches of Saipan were code-named colors: Yellow, Blue, Red and Green, split between the Second and Fourth Marine Divisions. Marines would assault their assigned beaches, in several waves. As the landing craft got close to the beach, the Japanese defenders opened up with machine-gun fire, artillery, antiboat guns and mortar barrages. Some of the amphibious tanks, tractors and boats were sunk by the Japanese before getting to the shore, but most craft made it to the beach in relatively good order. That’s when all hell broke loose, and for a time, chaos reigned.

Writing of his memory of the battle, then Marine Captain John C. Chapin wrote in 1994 that when he first made it to the beach he was stunned by what he saw and experienced. “All around us was the chaotic debris of bitter combat: Jap and Marine bodies lying in mangled and grotesque positions; blasted and burnt-out pillboxes.” The Marines had a carefully sequenced plan that required early waves of landing troops to push inland at certain intervals so subsequent waves could land. That didn’t happen.

From the outset it became clear that the massive pre-landing bombardments had caused only minor damage to the defenders and they were able to put up fierce resistance, resulting in delaying penetration into the island, stacking up Marines on the beach. Thousands of Americans were killed and wounded in the chaos of the initial landings. The amphibian tanks and armored tractors that were supposed to force penetration of the beach defenses largely failed, as the Japanese fire was able to knock many of them out, blocking the path for follow-on troops. The Second Marine Division suffered over 1,500 casualties by nightfall of the first day.

Yet despite the fierce shelling and machinegun fire from the Japanese, the Marines and later the U.S. Army’s Twenty-Seventh Infantry Division were just as fierce in their determination, and pressed the enemy further and further inland. After nearly three weeks of heavy fighting, it appeared the Americans had broken the back of the Japanese and final victory was near. But the Japanese authorities had given instructions to their commanders that there was to be no surrender. They must fight to the death. The 105th Infantry Regiment of the Twenty-Seventh Division was the unlucky victim of this order.

On July 7, intelligence reports indicated there were only a few thousand weak and starving Japanese troops left. The 105th Regiment, a national guard unit from New York, had set up a defensive line in the island’s interior. Suddenly out of nowhere came thousands of screaming Japanese running directly towards the American line. Since U.S. air and naval power had cut off any resupply for the defenders, most Japanese had run out of ammunition. Many of the attackers charged the American lines with samurai swords and bamboo poles with bayonets tied to the end.

In a 2014 interview with the Associated Press, then-twenty-year-old New York native Alfred Mailloux described what it was like when the attack began. “I was scared as hell. . . . When you hear that screaming—‘banzai’—who wouldn’t be?" The regiment suffered 406 killed and another 516 wounded. When the attack was over, however, a staggering 4,300 Japanese troops lie dead before the American line. Of the approximately thirty thousand Japanese troops on the island before the battle, barely nine hundred survived.

The Americans eventually completely expelled the Japanese from Saipan, but the war would go on, relentlessly, brutally, for another year. The vicious and comprehendible defense put up by the Japanese would be repeated on countless other islands and battles before the end came, in such places as Peleliu, Corregidor and Iwo Jima. Yet ultimately it was the equally tenacious and even more relentless American Marines and soldiers that ultimately proved decisive in the Pacific campaign.

Daniel L. Davis is a senior fellow for Defense Priorities and a former lieutenant colonel in the U.S. Army who retired in 2015 after twenty-one years, including four combat deployments.

Image: U.S. Navy heavy cruiser USS Indianapolis. Wikimedia Commons/U.S. Navy