by Daniel Wrinn
The mortar tube had a small muzzle cavity. It rested on a steel base plate supported by a wooden platform. Unlike typical mortars, this five-foot-long projectile was placed over the tube instead of dropping down the barrel. The mortar shell’s diameter was thirteen inches, while the tube was only a little more than ten inches wide.
This weapon hurled a 675-pound shell over 1,500 yards. The range was adjusted by varying the powder charge, while deflection changes were accomplished by brute force: pushing and shoving the base platform. Although tubes only held out for six rounds, enough shells were lobbed onto Allied positions to make a lasting impression.
A rifleman in the 28th Marines referred to it as “The Screaming Jesus.” Most Marines had a healthy respect for the mortar. General Robert Cushman, who commanded the 2/9 Marines on Iwo Jima (later becoming the 25th Commandant of the Marine Corps), recalled the inaccuracy and terror of the tumbling projectiles: “you could see it coming. But you never knew where the hell it was going to come down.”
Iwo’s Air Support
For a few memorable moments before the D-Day landing, the Marines’ vision of an integrated air-ground assault team became a reality. As assault troops neared the beach in their tracked amphibian vehicles, dozens of F4U Corsairs swept in and paved the way with rockets and machine-gun fire. According to one Marine: “it was magnificent.”
Unfortunately, the Marine fighter squadrons on Iwo Jima that morning came from the fast attack carriers of Task Force 58, not the amphibious task force. Three days later, Task Force 58 left for good in pursuit of more strategic targets. Following that, Navy and Army Air Force pilots provided support for the landing force fighting ashore. Sustained close air support of amphibious forces by Marine air was (once again) postponed for some future combat proving ground.
Other Marine aviation units contributed to the capture of Iwo Jima. One of the first to see action was VMB 612 (Marine Bombing Squadron) out of Saipan. Flight crews on PBJ Mitchell medium bombers ran long-range nightly rocket attacks against enemy ships trying to resupply. These nightly raids, along with the Navy’s submarine interdictions, slashed the amount of ammunition and fortifications (mostly barbed wire) delivered to the enemy before the invasion.
Pilots and aerial spotters from Marine observation squadrons flew in from escort carriers or were launched from the infamous LST 776’s slingshot. These crews played a crucial role in spotting enemy artillery and mortar positions and reporting them.
Marine transport aircraft based in the Marianas delivered critical combat cargo to the island at the height of the battle. Marines relied on aerial delivery before the landing force could establish a fully functional beachhead. On D +1, marine transport squadrons airdropped critically needed machine gun parts, mortar shells, and blood plasma within the lines. On March 3, Colonel Malcolm Mackay landed the first Marine transport aircraft on the island—a Curtiss Commando R5C loaded with ammunition. The three other Marine squadrons followed and brought in much-needed supplies and evacuated the wounded.
On March 8, Marine Torpedo Bomber Squadron 224 flew in from Tinian and took responsibility for day and night anti-submarine patrols. Colonel Vernon Megee had the honor of commanding the first Landing Force Air Support Control Unit (a landmark in the evolution of amphibious combat).
Megee came ashore on D +5 with General Schmidt, but the offloading process was still in such shambles that it took five days to gather communication jeeps. This did not deter Megee. He “borrowed” gear and moved inland to coordinate the Air Liaison Parties. He persuaded Navy pilots to use bigger bombs and listened to the assault commanders’ complaints.
McGee’s work in training and employing Army P-51 Mustang pilots was masterful. Kuribayashi transmitted to Tokyo “lessons learned” in defending against the Allied amphibious assault during the battle. One of his messages said: “the enemy’s air control is strong. At least thirty aircraft flew ceaselessly from early morning to night over this very small island.”
Sherman Zippo Tanks
For many Marines on Iwo Jima, the Sherman M4A3—with the Mark I flamethrower—was the most effective weapon employed in the battle.
On Iwo, Marines had come a long way with the tactical use of fire. Fifteen months earlier on Tarawa, only a handful of backpack flamethrowers were available to fight hundreds of the island’s fortifications. While the assault force relied on portable flamethrowers, most Marines saw the value in marrying this technology with armored vehicles for use against the island’s toughest targets.
In the Marianas, Marines modified M3A1 light tanks with the Canadian Ronson flame system to a deadly effect. But the small vehicles were vulnerable to enemy fire. On Peleliu, the 1st Marine Division mounted the improvised Mark I system on a thin skin LVT. But again, the vehicle’s susceptibility to enemy fire limited the effectiveness of the system. The obvious solution was to mount the flamethrower on a tank.
Early modifications to the Shermans were made by replacing the bow machine gun with the small E4-5 mechanized flamethrower. Replacing the bow machine gun was only a minor improvement. The short-range, limited fuel supply and awkward aiming process did not compensate for losing the machine gun. Each of the three tank battalions used the E4-5-equipped Shermans on Iwo Jima.
The best solution for effective flame projection and mechanized mobility came from the Army’s Chemical Warfare technicians on Hawaii before the invasion. Colonel Bill Collins, CO 5th Tank Battalion, inspired this tinkerer group to modify the Mark I flamethrower to operate within the Shermans’ turret. By replacing the 75mm main gun with a look-alike launch tube, this modified system could be trained and pointed like any standard turret gun using napalm-thickened fuel. These Zippo tanks streamed 250 yards of flame for eighty seconds—a significant tactical improvement.
But the modification team only had enough time to modify eight M4A3 tanks with the Mark I flame system. The 4th and 5th Tank Battalions were each issued four. The 3rd Tank Battalion on Guam didn’t receive any M4A3 Shermans nor field modifications in time for the battle on Iwo Jima. Although several of their A2 tanks kept the E4-5 system mounted in the bow.
The eight Sherman Zippo tanks were ideal against Iwo’s rugged caves and concrete fortifications. The enemy was terrified of this weapon. Suicide squads of human bullets would attack flame tanks directly only to be shot down by covering forces or charred by napalm. Enemy fire took a toll on the eight flame tanks—but maintenance crews worked around the clock to keep them in the fight.
Captain Frank Caldwell, Company Commander of the 26th Marines said: “it was a flame tank more than any other supporting arm that won this battle.”
The tactical demand for flame tanks never diminished. The 5th Tank Battalion used 10,000 gallons of napalm-thickened fuel a day. When the 5th Marine Division had cornered the last Japanese defenders in “The Gorge,” their final after-action report stated the flame tank was one of the weapons that caused the enemy to leave their caves and rock crevices and run for their lives.
Buck Rogers Men
Provisional rocket detachments were attached to the subdivisions of the landing force on Iwo Jima. Marines had a love-hate relationship with the little rocket trucks and their brave crews. These trucks were a one-ton, four wheel drive truck modified to carry three box-shaped rocket launchers containing a dozen 4.5-inch rockets.
Crews fired a ripple of thirty-six rockets within seconds and provided a carpet of high explosives on the target. While effective and deadly, each launch drew heavy return fire from the Japanese—who dreaded the automatic artillery.
The Experimental Rocket Unit was formed in June 1943 and first deployed rail-launched barrage rockets during the fighting in the Solomons. There, heavily canopied jungles limited their efficiency. But once mounted on trucks and deployed in the Central Pacific, these rockets were deadly and effective, especially during the battle on Saipan.
Marines reinforced the trucks’ tailgate to serve as a blast shield. They installed hydraulic jacks to raise and lower the l
aunchers. Crude steel rods were welded to the bumper and dashboard to help the driver align the vehicle with the aiming stakes.
A hilly treeless Iwo proved an ideal battleground for the “Buck Rogers Men.” The 1st Provisional Rocket Detachment supported the 4th and 5th Marine Divisions throughout the battle on Iwo Jima. The Buck Rogers Men fired over 30,000 rockets to support the landing force.
The Rocket Detachment landed on Red Beach on D-Day and lost one vehicle in the surf and several others to heavy enemy fire or loose sand. When the first vehicle reached its firing position intact, it launched a salvo of rockets against Japanese fortifications on the slopes of Suribachi. It detonated an enemy ammunition dump. The detachment supported the Marines advance to the summit, often launching single rockets to clear suspected enemy positions along the route.
As the fighting advanced north, the rocket launchers’ short-range deep angle fire and saturation effect kept them in high demand. They were effective in defilade-to-defilade bombardments. But the distinct flashing telltale blast always caught the attention of the Japanese artillery spotters. The rocket trucks rarely remained in one place long enough to fire more than two salvos. A fast displacement was critical to their survival. Marines knew better than to stand around and wave goodbye—it was time to seek deep shelter from the counter-battery fire sure to follow.
Logistical Support
The logistical effort necessary to sustain the assault force on Iwo Jima was complex, enormous, and learned from previous lessons in Pacific amphibious operations. No other element of the emerging art of amphibious warfare had improved so greatly by the winter of 1945.
While Marines had the courage and firepower to tackle a fortress like Iwo Jima, they would have been crippled without the available amphibious logistical support. The procedures, organizations, and concepts took years to develop. But once in place, they enabled the large-scale conquests on Iwo Jima and Okinawa.
On Iwo Jima, the 8th Field Depot was commanded by Colonel Leland Swindler. This depot served as the nucleus of shore party operations. Swindler coordinated the activities of all shore party operations. The logistical support on Iwo was well-conceived and executed. Liaison teams from the 8th Field Depot accompanied the 4th and 5th Divisions ashore. On D +3, field depot units came ashore, took over the unloading, and continued without interruption.
Every imaginable method of delivering combat cargo ashore was used. This involved “hot cargo,” carried in by the assault waves. Hot cargo was preloaded in on assault waves or floating dumps. This experimental use of one-shot preloaded amphibious trailers, Wilson drums, and a general loading and unloading would be known to future generations as the “assault follow-on echelon.”
Aerial delivery was first by parachute and then via transports landing on the captured runways. The Marine/Navy team experimented with the use of armored bulldozers and sleds loaded with hinged matting delivered by assault waves to clear wheeled vehicles stuck in the soft, volcanic sand. Despite fearsome obstacles: heavy surf, dangerous undertows, foul weather, and formidable enemy fire—the system worked. The combat cargo flowed in and kept casualties and salvaged equipment flowing out.
The occasional shortages were often the result of the Marines meeting a more robust defensive garrison than initially expected. Urgent calls for more demolitions, grenades, mortar illumination rounds, and blood plasma were common. Transport squadrons delivered many of these critical items directly from the Mariana Islands fleet bases.
The field medical support on Iwo was a model of detailed planning and flexible application. Marines received immediate medical attention from their corpsmen and surgeons. But the system from hospitals to grave registration was mind boggling to some of the older veterans. Moderately wounded Marines received full hospital treatment and rehabilitation—often returning directly to their units—this preserved some of the swiftly decreasing combat experience levels in the frontline outfits. The more seriously wounded were stabilized, evacuated, and treated in offshore hospital ships or taken by air to Guam.
Marines fired an extraordinary half-million artillery rounds to support the assault units. Many rounds were lost when the 5th Marine Division’s ammo dump blew up. But the flow never stopped. The shore party used LVTs and amphibious trucks for a fast offloading of ammunition ships dangerously exposed to enemy gunners. Marines helped the shore party hustle munitions onshore and into the neediest hands.
Colonel James Hittle of the 3rd Division (the reserve landing force) shook his head at the “crazy quilt” logistics adopted because of Iwo’s geography. Hittle “appropriated” a transport plane and made regular runs to Guam—returning with fresh beef, beer, and mail. Colonel Hittle sent his transport quartermaster out to sea in an LVT full of war souvenirs to trade for bread, eggs, and fresh fruit.
Hittle was amazed at the density of troops funneled onto the small island: “at one point, we had over 60,000 men occupying less than three and a half miles of broken terrain.” He directed Marine engineers to dig a well near the beach for a freshwater distilling plant. Instead of a saltwater source, engineers discovered steaming mineral water heated by Suribachi’s dormant volcano.
Hittle moved the distilling site, and this spot became a hot shower facility—one of the most popular places on the island.
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Operation Iceberg
1945 Victory on Okinawa
Seizing Shuri Castle
At dawn on May 29, 1945, the 1st Marine Division began their fifth consecutive week of frontal assaults. This was part of the Tenth Army’s relentless offensive against Japanese defenses in southern Okinawa.
Operation Iceberg’s mission to secure Okinawa was now two months old and badly bogged down. The fast-paced opening had been replaced by weeks of exhausting and bloody attrition warfare against the Shuri Castle.
The 1st Division were hemmed in between two other divisions. They had precious little room to maneuver and had advanced less than a thousand yards in eighteen days. An average of fifty-five murderous yards per day. Their sector was one bristling, honeycombed ridgeline after another—Kakazu, Dakeshi, and Wana.
But just beyond was the long shoulder of Shuri Ridge. Nerve center of the Imperial Japanese Thirty-second Army. The outpost of dozens of forward artillery observers, who’d made life miserable for the Allied landing force. On this wet, rainy, and cold morning, things were different. It was quieter. After days of savage and bitter fighting, Allied forces overran Conical Hill to the east and Sugar Loaf to the west. Shuri Castle no longer seemed invincible.
The 1/5 Marines moved out cautiously and expected the usual firestorm of enemy artillery at any moment. But there was none. Marines reached the crest of Shuri Ridge without a fight. Amazed, the company commander looked west along the road toward the ruins of Shuri Castle: a medieval fortress of ancient Ryukyuan kings.
Soldiers in the Tenth Army expected the Japanese to defend Shuri to the death, but the place seemed lightly held. Spiteful small arms fire came from nothing more than a rearguard. Field radios buzzed with this surprising news. Shuri Castle laid in the distance, ready for the taking. Marines asked for permission to seize their long-awaited prize.
General Pedro del Valle, CO of the 1st Marine Division, didn’t hesitate. According to corps division boundaries, Shuri Castle belonged to soldiers of the 77th Infantry Division. General del Valle knew his counterpart, Army General Andrew Bruce, would be furious if the Marines snatched their long-sought trophy before his soldiers could arrive. This was a unique opportunity to grab the Tenth Army’s primary objective. General del Valle gave the go-ahead, and with that, the 1/5 Marines raced along the west ridge against light opposition and secured Shuri Castle.
After General del Valle’s
staff did some fancy footwork to keep peace with their army neighbors, they learned the 77th had scheduled a massive castle bombardment that morning. Frantic radio calls averted the near-catastrophe just in time. General Bruce was infuriated by the Marines’ unauthorized initiative. Del Valle later wrote: “I don’t think a single Army commander would talk to me after that.”
Through the inter-service aggravation, Allied forces had achieved much this morning. For two months, Shuri Castle had provided the Japanese with a superb field of observed fire—covering southern Okinawa’s entire five-mile neck. But as the 1/5 Marines deployed into a defensive line within the castle’s rubble, they were unaware that a Japanese rearguard still occupied a massive subterranean headquarters underneath them. Marines soon discovered that directly under their muddy boondockers was the underground headquarters of the Japanese Thirty-second Army. This mammoth complex was over 1,200 feet long and 160 feet deep: all dug by pick and shovel.
The enemy had stolen a march on the approaching Tenth Army. Japanese forces retreated south during the rains and occupied the third (final) ring of their prepared underground defenses: a series of fortified escarpments on the Kiyamu Peninsula.
Seizing Shuri Castle was an indisputable milestone in the Okinawa campaign. Still, it was a hollow victory. Like the flag-raising on Iwo Jima’s Suribachi signified the end of the beginning of that prolonged battle. The capture of Shuri Castle did not end the fighting. The savage slugfest on Okinawa continued for another twenty-four days—while the plum rains fell and the horrors and dying on both sides continued.