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Operation Detachment: The Strategy

The United States followed its successful plan for amphibious assaults on enemy-held islands, while the Japanese countered with a defense entirely different than any they’d attempted before.

Take a world map, find the Mariana Islands in the Western Pacific, and draw a line roughly north by northwest from Saipan to Tokyo. If your map is detailed enough, about midway along the line and just to the west, you’ll discover a tiny spit of an island called Iwo Jima.

Like several other small Pacific islands, Iwo Jima would never have attracted the smallest footnote in even the most thorough history books if it weren’t for World War II. Yet Iwo, by virtue of its location, became a critical strategic objective to both the Allies and Japan. Furthermore, its capture exacted one of the bloodiest casualty tolls in Marine Corps history.

That’s a startling fact when you consider how small Iwo Jima really is. It has less than 8 square miles of land; by comparison, Guadalcanal has 2,180, Okinawa 454, Guam 209, and Saipan 45. But for nearly a month in early 1945, every square mile of Iwo Jima was a battleground, every square yard a killing field. To understand why, and how, it’s essential to appreciate what the island meant to both sides.

Despite being just 4 2/3 miles long and 2 1/2 miles wide, Iwo Jima is the largest and most important island in the Volcano Islands chain. Its shape is most often described as a pork chop, tilting slightly to one side, with the thick end pointing to the northeast, then tapering southwest to a narrow tip.

The highest spot on Iwo Jima is Mount Suribachi, which dominates the southern point. By geographical standards, it is little more than a hill, rising to an elevation of just 554 feet. However, to defending forces, it offered a tremendous open view to the southeastern beaches, which lie immediately below. There’s more high ground to the north, along with rugged terrain pockmarked with fissures, crevices, and ravines. In between the two extremes, the landscape is relatively flat; with a little work, it’s suitable for one or more airfields. Along both sides, black volcanic sand beaches rise sharply into a series of terraces before leveling off; one of those terraces, Chidori Haga, was the final resting place for dozens of Marines in the first hour of the assault.

In Japanese, iwo means sulfur (jima means island), and sulfur vents give the island the unmistakable smell of rotten eggs. The sulfur was one reason the Japanese settled Iwo; the volcanic soil is suitable for growing sugar cane, making a small sugar refining industry possible.

Japan annexed the Volcano Islands in 1887. On Iwo, a village called Motoyama took root. Even though it’s about 660 miles from the island to Tokyo, Iwo Jima is a prefect of Tokyo; technically, it’s a suburb of Japan’s capital.

 

Pictured from left to right, Capt. William H.P. Blandy, USN; Rear Adm. Harry W. Hill, USN; Lt. Gen. Holland M. “Howlin’ Mad” Smith, commander of U.S. Marines on the island; and Vice Adm. Richmond K. Turner, commander in chief of U.S. operations on Iwo Jima, examine a scale model of Iwo Jima as they discuss plans for attacking the heavily defended island fortress. U.S. NAVY PHOTO

Pictured from left to right, Capt. William H.P. Blandy, USN; Rear Adm. Harry W. Hill, USN; Lt. Gen. Holland M. “Howlin’ Mad” Smith, commander of U.S. Marines on the island; and Vice Adm. Richmond K. Turner, commander in chief of U.S. operations on Iwo Jima, examine a scale model of Iwo Jima as they discuss plans for attacking the heavily defended island fortress. U.S. NAVY PHOTO

 

That’s more than an incidental point. As Allied forces recovered from their early losses in World War II, they first had to retake land captured by the Japanese in their brutal war of aggression. The Japanese never ceded it easily at places such as Kwajalein, Tarawa, Bougainville, Peleliu, and Tinian.

With Iwo, they had even more for which to fight. This was their land, the first of the Japanese Home Islands to be assaulted. They also recognized that the fall of Iwo Jima would unlock a critical gateway to subsequent attacks on mainland Japan. “This island is the front line that defends our mainland, and I am going to die here,” Japanese commander Lt. Gen. Tadamichi Kuribayashi told Radio Tokyo prior to the American invasion.

For the Japanese, Iwo Jima had to be defended at any cost. Kuribayashi determined to make Iwo Jima the most formidable fortress and bloodiest defense in his nation’s history.

In his view, it was a matter of national honor – and national survival.

 

THE AMERICAN PURPOSE

For the Allies, there was a more immediate and practical reason to take Iwo Jima away from the Japanese and begin using it themselves. The Mariana Islands had finally been recaptured in the summer of 1944. Almost immediately, squadrons of B-29 Superfortress bombers, an awesome new addition to the U.S. arsenal, began launching from Saipan, Tinian, and Guam to make runs on Tokyo, Yokohama, and other sites in Japan.

The objective was to cripple Japan’s war-making industry and infrastructure, and the missions were working. But it was a 3,000-mile round-trip flight, which Japanese fighters didn’t make pleasant. From newly built bases at Iwo and elsewhere, they were waiting to ambush the B-29s, sometimes on the inbound trip but more often on the return leg. Any bomber crippled by enemy fire, or plagued by fuel or mechanical problems, had no friendly alternatives. The losses in crews and machines were devastating and couldn’t be sustained indefinitely. Both the Army Air Corps and Adm. Chester Nimitz, commander in chief of the Pacific Fleet, decided it was essential to take Iwo.

Still, that decision didn’t make an attack a certainty. Gen. George Marshall, the head of the Joint Chiefs of Staff, favored an Iwo invasion and had ordered it for early 1945 under the code name Operation Detachment. However, Gen. Douglas MacArthur opposed the plan, as did Chief of Naval Operations Adm. Ernest J. King, who strongly believed Formosa should be the next stepping-stone to Japan. King planned to change Marshall’s mind, but he didn’t get the support of the on-site commanders, including Army Lt. Gen. Simon Bolivar Buckner and Millard F. Harmon. They agreed with Nimitz that an invasion of Iwo followed by a landing on Okinawa were the most logical next steps in the long Central Pacific campaign to bring the war to Japan’s doorstep. It took a candid meeting in October 1944 to decide the issue.

King was convinced. He returned to Washington, consulted with the other Joint Chiefs, and Operation Detachment was on.

 

JAPANESE PLAN CHANGES

The Japanese were unaware of these behind-the-scenes machinations. It was already clear to their strategists that Iwo would one day be an asset and a target. In early 1943, they began improving its offensive and defensive capabilities by building an airstrip, tunnels, gun emplacements, and pillboxes into Iwo’s soft volcanic soil.

 

Lt. Gen. Tadamichi Kuribayashi determined to make Iwo Jima the most formidably defended island America would invade during the Pacific war, and the bloodiest. DEPARTMENT OF DEFENSE IMAGE

Lt. Gen. Tadamichi Kuribayashi determined to make Iwo Jima the most formidably defended island America would invade during the Pacific war, and the bloodiest. DEPARTMENT OF DEFENSE IMAGE

 

These preparations continued into 1944 and included a second airstrip and the start of construction on a third. However, the decision with the most far-reaching consequences came in May 1944. That’s when Japan’s supreme military commander, Gen. Hideki Tojo, named Kuribayashi to take command of Iwo Jima. Tojo told the descendent of the samurai warriors and 30-year army veteran: “Only you among all the generals are qualified and capable of holding this post … The entire army and the nation will depend upon you for the defense of that key island.”

Like Adm. Isoroku Yamamoto, who planned the attack on Pearl Harbor, Kuribayashi had spent a good deal of time in the United States. He had even engaged in some cavalry training at Fort Bliss, Texas, in the 1920s. Like Yamamoto, he clearly understood what a formidable, determined foe the United States would be. Kuribayashi had once written to his wife: “The U.S. is the last country in the world Japan should fight. Its industrial potential is huge and fabulous, and the people are energetic and versatile. One must never underestimate the American fighting ability.”

 

One of several sketches prepared by the 31st U.S. Naval Construction Battalion of Japanese tunnel systems and fortifications. The sketch shows the north face and top of Hill 362A on Iwo Jima. Dotted lines indicate the underground Japanese tunnel system. This paled by comparison with the 7 stories of tunnels just within Mount Suribachi. More than 15 miles of tunnels were dug into an 8-square-mile island. U.S. NAVY IMAGE

One of several sketches prepared by the 31st U.S. Naval Construction Battalion of Japanese tunnel systems and fortifications. The sketch shows the north face and top of Hill 362A on Iwo Jima. Dotted lines indicate the underground Japanese tunnel system. This paled by comparison with the 7 stories of tunnels just within Mount Suribachi. More than 15 miles of tunnels were dug into an 8-square-mile island. U.S. NAVY IMAGE

 

In June 1944, the 54-year-old Kuribayashi, a former commander of the elite Imperial Guard, arrived on Iwo and almost immediately made a fateful decision. Iwo’s artillery, in accordance with Japanese doctrine, was positioned by Kuribayashi’s predecessors to attack the beaches. A then-classified American military intelligence brief, “Japanese Defense Against Amphibious Operations,” stated the philosophy of this plan, explaining that the Japanese “have a strong aversion to [being on] the defensive,” and that they try to terminate defensive operations by “whittling down the superiority of the enemy until they can revert to the offensive and force a decision by assault.” The document further stated, “Their mission is to annihilate the enemy forces before a landing can be effected, or as soon after the initial landings as possible.”

Kuribayashi countermanded the plan. He did so against the opposition of the more traditional navy and army officers on Iwo. He ordered the artillery pulled back and hidden at the foot of Mt. Suribachi and elsewhere. He used every ridge, cave, hill, and crevice Iwo gave him. He had learned the lessons taught at Normandy and in the Marianas: You could not stop an invasion on the beaches indefinitely, no matter how strong the defense. Therefore, the Japanese would conserve resources and inflict as much pain on the enemy as possible for as long as possible. “Above all, we shall dedicate ourselves and our entire strength to the defense of the islands,” he added.

It was a brilliant decision.

 

AMERICANS ASSEMBLE INVASION FORCE

As Kuribayashi built his defenses, American planners were putting together a massive, seasoned invasion force. There would be 485 ships involved in the invasion, including 12 aircraft carriers, and another 300 offensive and support ships within 100 miles of the Iwo Jima shoreline. This task force, under the overall command of Rear Adm. Raymond A. Spruance and the tactical command of Vice Adm. Richmond Kelly Turner, wasn’t just targeting Iwo Jima:

It would also launch air attacks on Japan’s major cities.

Early on, a decision was made to land on Iwo’s eastern beaches, although the water was actually more shallow on the west and the ground slope more gradual.

 

This shelter was captured without damage. Though sparse in amenities, structures like this offered their Japanese inhabitants one comfort that was not enjoyed by any Marines on Iwo Jima: the protection of thick concrete walls. U.S. MARINE CORPS PHOTO

This shelter was captured without damage. Though sparse in amenities, structures like this offered their Japanese inhabitants one comfort that was not enjoyed by any Marines on Iwo Jima: the protection of thick concrete walls. U.S. MARINE CORPS PHOTO

 

The Marine assault force on Iwo would have 70,647 men. The senior Marine in the Pacific was Lt. Gen. Holland “Howlin’ Mad” Smith, considered by most to be the foremost military expert anywhere on amphibious landings. A fierce Marine partisan, Smith had not endeared himself to either the Navy or the Army in previous campaigns. Consequently, while Smith had overall command, the Iwo Marines would actually be led by Maj. Gen. Harry Schmidt, who now headed the V Amphibious Corps (VAC) and had previously commanded the 4th Marine Division.

There would be three Marine divisions – the 3rd, 4th, and 5th – in the landing force. The 3rd Division was commanded by Maj. Gen. Graves B. Erskine, one of the youngest and among the toughest generals in the Marines. He would be leading forces who had already proven themselves at Bougainville, Guam, and other islands.

Maj. Gen. Clifton B. Cates was now in charge of the 4th Marine Division. He was a fitting commander for a division that had been in four campaigns in less than a year. During World War I, Cates had sent a classic message from the front that said simply, “I have no one on my left and only a few on my right. I will hold.”

 

 

Maj. Gen. Keller E. Rockey headed the 5th Marine Division, which had been formed in early 1944 and had yet to see combat. But some 40 percent of its Marines were battle-hardened veterans, and Rockey had also distinguished himself on the battlefields of France in World War I.

Early on, a decision was made to land on Iwo’s eastern beaches, although the water was actually more shallow on the west and the ground slope more gradual. However, the east offered better surf conditions, and the Navy preferred the water conditions there for bringing in ships for landing and fire support.

The 3,500 yards of beach were divided into segments: from the south (or left) there was Green, Red 1 and 2, Yellow 1 and 2, and Blue 1 and 2. The 5th Division would come in on the left and the 4th on the right, while the 3rd Division was held in seagoing reserve.

With an entire ocean of bloody amphibious landings to use as hindsight, the Marines wanted as much bombardment as possible just before the invasion. More than two months before the invasion, intense bombing began. Schmidt then asked for 10 days of withering pre-invasion bombardment from battleships and cruisers.

In one of the most bitterly controversial decisions of the campaign, the request was denied. Turner said that such a bombardment would jeopardize the Navy’s larger mission against Japan. As a result, there would be just three days of pre-landing bombardment.

 

** U.S. Army Air Forces B-24 Liberators bomb Iwo Jima, Dec. 15, 1944. This raid of December 15 was one of a series of bombings of the vital Japanese airfields on the island. Mt. Suribachi is the volcano at the lower tip of the island. Allied air attacks hammered the island for 74 days before the actual invasion. NATIONAL ARCHIVES PHOTO

U.S. Army Air Forces B-24 Liberators bomb Iwo Jima, Dec. 15, 1944. This raid of December 15 was one of a series of bombings of the vital Japanese airfields on the island. Mt. Suribachi is the volcano at the lower tip of the island. Allied air attacks hammered the island for 74 days before the actual invasion. NATIONAL ARCHIVES PHOTO

 

There’s little question that the decision cost lives. Yet that didn’t mean the Japanese on Iwo would have the luxury of building their defenses in complete freedom. In November, B-24s and B-29s from the Marianas had begun hammering the island, and had been later joined by carrier planes. The attacks had continued for a record 74 days and dropped nearly 6,000 tons of high explosives.

It’s difficult to conceive that any large force – squeezed into 8 square miles – could survive such a sustained pounding and remain battle-ready.

On Iwo Jima, one did.

 

THE JAPANESE UNDERGROUND SYSTEM

Under Kuribayashi’s command, fortification engineers and cave specialists came from Japan and drew up specifications for construction of a cave system that would be the backbone of the Japanese defense. Caves varied in capacity from three men to 300- 400 men, and were meticulously planned so that frontal shells could not hit their entrances directly. Furthermore, the caves were carved out or reshaped with multiple entrances to permit escape; all were stocked with food and water. Huge amounts of concrete and reinforcing iron were shipped in from Chichi-Jima, the island commanded by Maj. Yoshitaka Horie that was 150 miles from Iwo Jima. All available scrub oak trees were cut down; additional wood was procured from buildings throughout the island. The man-made caves were 30-40 feet deep and had stairways, interlaced corridors, and passageways.

Japanese soldier interviews and diaries reveal the bombing and shelling did take a toll. But the work of turning Iwo into an almost impregnable fortress would simply pause and then start anew.

The Japanese and 1,000 Korean laborers dug more than 15 miles of tunnels into the earth. In many places, it was so hot underground that a man could dig for only 5 minutes or so. The tunnels interconnected, providing a latticework of channels that could be used for communications, supplies, and the rapid movement of troops to new fighting positions.

Due to Kuribayashi’s network strategy, which emphasized maximum coverage and crosscoverage of terrain with maximum force, the defenders could fire artillery from any place on the island to any other; the only thing to block it was terrain.

On the surface, more and more pillboxes were added until there were some 800 entrenched around the island. Along with them were 730 major defense installations, 120 guns larger than 75 mm, 130 howitzers, 90 large mortars and rocket launchers, 16 anti-tank guns, 200 20 mm machine guns, and 24 tanks. All installations and weapons armories were connected by tunnels.

The American military intelligence brief “Japanese Defense Against Amphibious Operations,” was very clear as to the difficulty this strategy entailed in prior engagements: “Bombardment was not very effective against these cave positions [on Guam], and it usually was necessary to dislodge the Japanese with demolition procedures, smoke, flame throwers, and grenades.”

 

An infantry battalion from the 3rd Marine Division moving up to the relief of another battalion during the fierce struggle for Iwo Jima. U.S. MARINE CORPS PHOTO

An infantry battalion from the 3rd Marine Division moving up to the relief of another battalion during the fierce struggle for Iwo Jima. U.S. MARINE CORPS PHOTO

 

Kuribayashi was laying down the gauntlet for a bloody, potentially demoralizing battle. He sensed that his force of 21,000 men had no chance to win the Battle of Iwo Jima, but he would not perish without the ultimate of fights: He ordered each of his men to take 10 American lives in exchange for his own.

 

NEW JAPANESE BEACH STRATEGY

The Japanese did not attempt to organize a beach defense. A large number of weapons, sighted to rake the shore line, were emplaced inland. When the Americans landed, they encountered no resistance until precisely 3 minutes later – the time when Kuribayashi predicted that enough Marines would be on the beaches to sufficiently overpopulate them and create confusion in the event of intense gunfire. He also had studied the thick volcanic sands of the invasion beach, and concluded that mechanized vehicles would bog down – slowing the Americans’ initial movement from the beachhead. Finally, he waited until the lead battalions tried to cross the eastern terrace just beyond the landing lines.

He was right on all counts.

The Japanese opened fire with artillery pieces, rocket launchers, anti-tank guns, and machine guns from Mt. Suribachi. From the right flank of the plateau-like tableland on eastern beaches came automatic weapons that swept back and forth across undefended beaches. There were also the pillbox installations, made of steel and reinforced concrete – most of which were invisible from the sea. They were situated to flood the beaches with heavy fire.

Due to Kuribayashi’s network strategy, which emphasized maximum coverage and cross-coverage of terrain with maximum force, the defenders could fire artillery from any place on the island to any other; the only thing to block it was terrain.

Every method of classic tactical defense was employed, along with some novelties. For example, aircraft bombs were carefully laid as tank mines. Arrays of mortars were buried up to their tubes, so that one man might reload them all in rapid succession.

“Spider moles” and caves linked to the tunneling system were everywhere, giving the defenders countless places from which snipers could appear, attack, disappear, and attack again from an entirely different location. With months to plan and prepare, overlapping lines of fire could be carefully coordinated, sights set, ranges measured, and troops trained.

The Japanese organized the entire island for defense with available forces, which included 21,000 men representing the 109th Infantry Division, Kuribayashi’s outfit; the 2nd Independent Mixed Brigade, which had five separate battalions; the 145th Infantry; a battalion from the 17th Regiment; the 26th Tank Regiment; and 7,000 navy troops.

 

A SAD REALIZATION

The landing was set for Monday, Feb. 19. As the task force formed, Howlin’ Mad Smith spent sleepless nights thinking about his Marines who would be lost on Iwo Jima. He’d looked at the aerial photos. The intelligence was good. He knew how well the Japanese were fortified, and he’d seen what they’d done at Tarawa, where 1,027 Marines had died in four days and only 17 of 4,700 defenders had surrendered.

 

U.S. Marines gain a few minutes’ respite from enemy fire by taking shelter in the entrance to a burned and captured Japanese pillbox. Note the effects of hits in the oil drums and the concrete pillbox. U.S. MARINE CORPS PHOTO

U.S. Marines gain a few minutes’ respite from enemy fire by taking shelter in the entrance to a burned and captured Japanese pillbox. Note the effects of hits in the oil drums and the concrete pillbox. U.S. MARINE CORPS PHOTO

 

It would be much worse this time, thought the world’s foremost expert on amphibious landings. He expected 15,000 casualties, an estimate that went far beyond what the theater’s other senior commanders were forecasting.

Sadly, even Smith was too optimistic.

 

COURAGEOUS BATTLE VOW

Kuribayashi continued to exhort his forces and prepare them for the coming battle. He had asked for enough men, planes, and ships to hold Iwo indefinitely. He didn’t get them. The inexorable advance of American forces in the Pacific had severely damaged the once-mighty Japanese navy and forced the Japanese high command to leave self-sustaining divisions on each remaining island. Noted an American military intelligence report, “Their localized defense of a particular island is conceived of as an integral part of the strategic perimeter defense of the vast Japanese Empire as a whole. The island divisions are expected to prevent hostile landings, counterattack and destroy such hostile beachheads as may be established despite their defenses, and conduct counterlanding operations.”

Also, they were to fight to the death. Kuribayashi hoped to make the capture of Iwo so costly that the Allies would decline to ever invade Japan. In the pillboxes could be found the “Courageous Battle Vow,” with these closing lines: “Each man will make it his duty to kill 10 of the enemy before dying. Until we are destroyed to the last man, we shall harass the enemy by guerrilla tactics.”

A few Japanese soldiers may have hoped for a reprieve, or at least reinforcements. Kuribayashi’s wife thought her husband might be transferred, considering his status in the army. But the general had no illusions. He spent the few months before the invasion instructing his wife on handling their family affairs, and admonishing his children to get the best possible education. In January he wrote to his wife, “No one here expects to return alive, but we are determined to do our best. Do not plan for my return. Do not be surprised when you hear that I have died.”

 

A COMPLETE PREPARATION

In size and scope, the assault on Iwo Jima would not compare to the invasion of Europe – Operation Overlord – conducted the previous June.

While both the heroism and losses at Normandy were on a huge scale, the Allied landing force there did have one advantage: The German defenders didn’t know when or where they were landing. There were literally hundreds of miles of beach to fortify and watch. In addition, the Allies went to great lengths to mislead the German high command. Moreover, the senior German commander, Field Marshall Erwin Rommel, was absent from Normandy when he was needed most.

Lt. Gen. Holland M. Smith, commander of the expeditionary troops in the Iwo Jima operation, and his chief of staff, Col. Dudley S. Brown, survey the bogged-down, surf-battered wreckage that marked the landing of the Marines on Iwo Jima. While Navy Adm. Chester W. Nimitz thought Iwo Jima would be taken without a fight, Smith feared the Marines would take up to 15,000 casualties. The reality was far worse. U.S. MARINE CORPS PHOTO

Lt. Gen. Holland M. Smith, commander of the expeditionary troops in the Iwo Jima operation, and his chief of staff, Col. Dudley S. Brown, survey the bogged-down, surf-battered wreckage that marked the landing of the Marines on Iwo Jima. While Navy Adm. Chester W. Nimitz thought Iwo Jima would be taken without a fight, Smith feared the Marines would take up to 15,000 casualties. The reality was far worse. U.S. MARINE CORPS PHOTO

In contrast, the soldiers on Iwo Jima were alerted as soon as the amphibious forces left their ports. They’d recognized the continuous air and naval bombardment as a pre-invasion warning. They could see all their beaches in a single sweep from high ground. Most of all, their determined leader was in place.

As an American report noted after the battle, the preparedness of the Japanese and Kuribayashi’s strategic brilliance set the tone for Iwo Jima: “The enemy, by continuing to follow his basic defensive tactic of occupying a position and refusing to yield until dug out and killed without counterattacking and without withdrawing, was able to maintain organized resistance for over 20 days … it is now known that this defense of holding to the end without counterattack or withdrawal was the express plan conceived by Kuribayashi despite the contrary advice of his Chief of Staff, Maj. Horie. It was this simple tactic, coupled with the incredible rocky terrain and the maximum use the enemy had made of this terrain in constructing fortified positions, which made the capture of Iwo Jima so difficult.”

So there could be no offensive surprise nor deception on Iwo. The Japanese knew where the Americans were landing, when they were coming, and how they would wage battle.

Bob Yehling also contributed to this story.

 

This story is from Uncommon Valor: The 75th Anniversary of the Battle of Iwo Jima.

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