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Kamikazes: Stopping the “Divine Wind” By Tom Laemlein

Kamikaze! Even 80 years later, the term still snaps men to attention. The word has become embedded in our language and is still used to describe any vehicle that purposefully executes an attack against a target that ends in its own destruction. In the ongoing war in Ukraine, modern “kamikaze drones” hover above the battlefield, guided by remote pilots to crash into a wide range of targets below.

A Japanese kamikaze crashes into the USS Missouri (BB-63), an Iowa-class battleship, during the final months of World War II. Image: NARA
A Japanese kamikaze crashes into the USS Missouri (BB-63), an Iowa-class battleship, during the final months of World War II. Image: NARA

While the military concept remains the same, the level of terror for the men facing the hell-bent missiles is quite different. The flesh-and-blood Allied sailors that faced the kamikazes fought for their lives against an opponent willing to sacrifice his own life to kill them. It was a visceral, primal form of combat within the context of a modern war.

One Plane/One Ship

Earlier in WWII, conventional air attacks against Allied surface vessels met with varying degrees of success. By late 1944, the U.S. Navy had achieved operational air and surface superiority over their Japanese opponents. kamikaze attacks threatened to change that dynamic.

Japanese kamikaze pilots gather before their final mission, receiving final instructions and blessings. This was a post-war photo created as an example. Image: NARA
Japanese kamikaze pilots gather before their final mission, receiving final instructions and blessings. This was a post-war photo created as an example. Image: NARA

Nearly 20% of all Japanese suicide attack planes were successful — and when they struck, they caused massive damage. Research shows that 47 U.S. ships were sunk by kamikaze air attacks, with dozens more damaged.

Beginning in October 1944, and carrying on until the end of the war, the kamikazes made a huge impression on the U.S. Navy as well as the future of naval combat.

For this article, I researched the weapons and tactics the U.S. Navy used to protect its ships and men against what the Japanese called the “Divine Wind”.

A Japanese Mitsubishi A6M2 “Zeke” kamikaze aircraft begins its fatal dive toward a U.S. Navy ship during the Marianas campaign. Image: NARA
A Japanese Mitsubishi A6M2 “Zeke” kamikaze aircraft begins its fatal dive toward a U.S. Navy ship during the Marianas campaign. Image: NARA

The Japanese term “kamikaze” comes from a national legend rooted in meteorology and military history. In the autumn of 1274, the Mongol empire sent a massive invasion fleet, stated to be nearly 1,000 ships, to conquer Japan. Fierce resistance by the samurai caused the Mongol troops to bog down, and then to withdraw to their ships in waters off Kyushu. The sudden appearance of a typhoon destroyed much of the Mongol fleet and miraculously ended the threat.

Seven years later, the Mongols returned, this time with a fleet of supposedly more than 4,000 ships. However, in the intervening years, the Japanese had constructed high walls and other beach obstacles. Unable to find a suitable landing zone, the Mongols lingered for months off the Japanese coast, their men depleted by hunger and illness. And again, a massive typhoon appeared and devastated the Mongol fleet. Most of the survivors were killed by the Japanese.

A Yokosuka P1Y “Frances” kamikaze descends toward the escort carrier USS Ommaney Bay (CVE-79) during World War II. Image: NARA
A Yokosuka P1Y “Frances” kamikaze descends toward the escort carrier USS Ommaney Bay (CVE-79) during World War II. Image: NARA

By World War II, almost every Japanese knew the legends of the “divine winds” that had twice saved their island nation from a huge invasion fleet. It is little wonder then that kamikaze was the name given to the men who would sacrifice their aircraft and their lives to attempt to save Japan with a miracle once again.

This article compiles excerpts from U.S.N. intelligence reports regarding the defense against suicide attack planes.

Types of Ships Targeted

In addition to the destroyers and carriers, nearly every other type of fleet unit has been attacked, including transports, landing craft, merchant ships, minesweepers, battleships, cruisers, tenders, patrol boats and hospital ships. Even an attack on a submarine by a suicide plane has been reported.

A Japanese Yokosuka D4Y “Suisei” dive bomber burns as it plummets toward the sea in 1945. Image: NARA
A Japanese Yokosuka D4Y “Suisei” dive bomber burns as it plummets toward the sea in 1945. Image: NARA

A POW who volunteered as a suicide pilot, but failed in his mission, stated that he was ordered to “crash-dive on any large ship”, with preference in this order: Carriers, battleships, cruisers, transports. He denied that there was a deliberate policy of wearing down picket ships, insisting that all suicide attackers prefer to attack larger ships, but sometimes cannot get through the AA fire.

The Japanese Army Training Manual indicates that the targets will be chosen by the senior commander by stating: “The TO Force (ED: “TO” is an abbreviation for TOKUBETSU meaning “special” and referring to the suicide plane units) must sink without fail the targets selected by order of the senior commander, without regard to the size or type of the enemy vessel.” The manual makes no recommendations concerning the types of vessels to be hit. The selection of types will naturally depend upon the local tactical situation and, for this reason, has probably been excluded from the book. The only type of vessel with which the manual appears to be concerned is the carrier. A chart showing the possible armament and vulnerable points on the ESSEX-class carrier is included in the manual. In addition, the text cautions personnel to learn to distinguish carriers from tankers and landing craft.

Evasive Tactics

The report of the USS Kimberly (DD-521), describing an attack which occurred on the afternoon of March 25, 1945 off Kerama Retto, describes the hard-turning evasive maneuver of the destroyer:

A Nakajima B5N “Kate” bomber dives toward a U.S. aircraft carrier in a kamikaze attack late in World War II. The torpedo plane was repurposed for suicide missions as Japan’s air forces dwindled. Image: NARA
A Nakajima B5N “Kate” bomber dives toward a U.S. aircraft carrier in a kamikaze attack late in World War II. The torpedo plane was repurposed for suicide missions as Japan’s air forces dwindled. Image: NARA

“At this time (after bogies were picked up) emergency flank speed was rung up and fire was opened on the VALs on a relative bearing of 0700 at advanced range of 7500 yards. Both VALs turned away, proceeded outside effective gun range and firing was ceased. Almost simultaneously with “cease firing”, one of the VALs peeled off and began to close the range on a converging but nearly opposite course. Fire was immediately re-opened and the rudder put hard right to maintain all guns bearing as the relative target bearing rapidly dropped aft. During this phase of the approach, the fire control problem was one of an extremely high deflection rate which the pilot further complicated by resorting to radical maneuvers, including zooming, climbing, slipping, skidding, accelerating, decelerating and even slow rolling.

He continued to close the range on a circling course, indicating his intention to get on our “tail” and further indicating to all observers his ultimate intention. By this time the range had closed to 4000 yards and all bearing 40 mm mounts opened fire. The plane was now in a vertical right bank, circling to come in from astern. The target seemed to be completely surrounded with 5-inch bursts and 40 mm tracers.

At about 1500 yards range on relative bearing 1700 he leveled off and came straight in at an altitude of about 150 feet, performing continuous right and left skids. The ship was still turning with full right rudder, but the target skidded to always remain inside the ship’s wake. At 1200 yards all the bearing 20 mm guns opened fire, and at about this same time the previously faint line of smoke coming from the plane became a positive stream of black smoke, but still the target kept coming.

Now only the after guns would bear and each 5-inch salvo blasted the 20 mm crews off their feet. Despite this difficulty, at the instant the VAL passed over the stern, the 20 mm guns had managed to empty one complete magazine. The plane was now about 100 feet in the air and apparently headed for the bridge with 40 mm guns Nos. 3 and 5 still firing at maximum rate. Just as the plane reached a point above 40 mm gun No. 5, it went out of control and fell nearly vertically between 5-inch mounts Nos. 3 and 4 crashing into the still rapidly firing guns of 40 mm mount No. 5.

The intensity of the explosion and the nature of the damage indicated that the VAL was armed with a bomb with an instantaneous fuse. The estimated size of the explosive was about 200 pounds.”

Four crewmen of the Kimberly were killed, and 57 wounded, during this attack.

Types of Attacks

Generally, the approaches are of four different types. In one, the suicide plane picks the target from long range and makes a long, straight dive from about five miles. Escorting planes disperse and turn back to confuse the radar. Other planes hide in the cloud cover after their escorts have left, then dive on unsuspecting ships.

A Yokosuka P1Y “Frances” twin-engine bomber dives toward a U.S. Navy ship during a kamikaze attack in 1945. The aircraft’s size made it one of the deadliest suicide planes of the Pacific War. Image: NARA
A Yokosuka P1Y “Frances” twin-engine bomber dives toward a U.S. Navy ship during a kamikaze attack in 1945. The aircraft’s size made it one of the deadliest suicide planes of the Pacific War. Image: NARA

Some attacks have been coordinated with high-level bombers that draw attention away from the suicide attackers. The fourth, and most common, is the low-level approach. In this, planes come in low over the water, then climb steeply for their final dive so that radar and fire control seldom have sufficient time to take effective action.

Charts and text of the captured Japanese Army manual give additional details of three types of approach; the horizontal, the diving, and the bow-on. In addition, the document recommends that “while advancing every effort must be made to take good advantage of local weather conditions, that is of clouds, sun and wind direction, with due regard for general climatic conditions. This will be especially the case in daylight and surprise attacks.”

The document states that the formation for the advance “will depend on conditions, particularly on the attack method, on the strength used and on the dispositions of the enemy.” It is particularly advantageous, the manual states, “to deceive the enemy by adopting formations and maneuvers which resemble those of his carrier-borne aircraft.”

“As soon as the attack targets are discovered, the pilots will first pull the fuse arming vane release handle and then close the attack on the enemy by diving down on him at full speed. At this time, every effort must be made to avoid losses from the enemy CAP and AA barrage by appropriate plane maneuvers. The run-in for steep diving attack will differ with the type of plane, but the approach to the enemy will be at high altitude. Then altitude and speed will be successively adjusted — this varies with the situation, but it will be best to adjust the speed twice — at 6000 meters and 4000 meters.”

Concerning the low-level attack, the manual states: “In the run-in for an extreme low level horizontal attack, the enemy will be approached at high altitude and then by rapid plane maneuvers, speed and altitude will gradually be adjusted.

Rows of grounded Japanese A6M “Zeke” fighters sit on an airfield with their propellers removed after Japan’s surrender. The planes were disabled to prevent any kamikaze missions. Image: NARA
Rows of grounded Japanese A6M “Zeke” fighters sit on an airfield with their propellers removed after Japan’s surrender. The planes were disabled to prevent any kamikaze missions. Image: NARA

A very low-level horizontal attack in a surprise raid when the cloud height is low will use either a diving or horizontal collision, depending on conditions at the time, and will be made with plane types such as Ki 67 (Peggy), Ki 45 (Nick), etc., at night, dawn or dusk.”

BAKA

Those who have observed BAKA attacks say that a trail of “light brownish smoke” comes from the bomb just before its release from the mother plane. As the BAKA is launched, the bomber veers off, showing its underside to the target. The smoke continues to trail BAKA in its path to the target. It was observed in some reports that at times the smoke can still be seen when the bomb is almost invisible because of its high speed. One report cautioned gunners who see smoke but no bomb to expect a low approach over the water.

An intact Yokosuka MXY-7 Ohka (aka “Baka”) rocket-powered kamikaze aircraft captured by U.S. troops on Okinawa in 1945. The manned bomb was designed for one-way suicide missions. Image: NARA
An intact Yokosuka MXY-7 Ohka (aka “Baka”) rocket-powered kamikaze aircraft captured by U.S. troops on Okinawa in 1945. The manned bomb was designed for one-way suicide missions. Image: NARA

Although combat experience with the BAKA was still relatively slight at that point, encouraging reports had come from the Fleet, indicating that the rocket bomb could be brought down by anti-aircraft fire. In one instance, a DM (converted minelayer) splashed a BAKA with a 5-inch gun, and, in another, an AM (auxiliary mine layer) blew one apart with a 40 mm battery.

Types of Explosives Carried

Explosives carried in suicide planes ranged widely. In the earlier attacks, mortar shells, artillery shells and other miscellaneous types of ammunition were found in wrecked planes. Then, it had been customary for kamikazes to carry a 250 kg bomb.

Japanese kamikaze suicide plane disintegrates in flames after hitting USS Intrepid (CV-11) during operations off the Philippines in November 1944. Image: U.S. Navy
Japanese kamikaze suicide plane disintegrates in flames after hitting USS Intrepid (CV-11) during operations off the Philippines in November 1944. Image: U.S. Navy

At times, the planes crashed without releasing the bombs, but later the tendency had been to release the bomb, either on another ship, or just before crashing. In some instances, the bombs exploded before the planes hit, either because of the pilots’ action or because they were hit by AA fire. Some suicide planes also had carried torpedoes, sometimes inside the plane. In one case, the torpedo was released just before the plane crashed and exploded within the ship. In another instance, a suicide plane carried an eight-inch shell as its explosive, but such cases were much rarer than they were when the kamikaze attacks first started.

Pilot Quality

The quality of the suicide pilot varies. One POW claimed he was flying his first combat mission. In contrast, many pilots demonstrated lengthy flying experience by their skillful evasive tactics and careful deliberation in their choice and approach to targets. One pilot’s blouse, recovered after a suicide attack, indicated that he was a carrier pilot, the most experienced type of Japanese airman. He was wearing a ribbon with two stars, possibly for combat experience. One action report noted that the Japanese were using more experienced pilots for suicide dives off Okinawa than they did in the Philippines.

Japanese kamikaze pilots gather in a dimly lit room as officers brief them on the next day’s mission. Image: U.S. Navy
Japanese kamikaze pilots gather in a dimly lit room as officers brief them on the next day’s mission. Image: U.S. Navy

The answer is that Japan uses any pilot who volunteers or might order any others on such a mission. The quality of such a group naturally varied widely. There was no evidence, however, to show that the best of Japan’s pilots were exempt from kamikaze squadrons to fly more orthodox combat missions. Some pilots doubtlessly volunteered in the belief that the Japanese warrior gains automatic enshrinement and a future life as a protecting deity (Kami) of Japan if he made this supreme gesture of devotion.

U.S. Navy Defense Recommendations

Numerous recommendations for countermeasures were made by officers of the Fleet who had experienced suicide attacks. Many were already being tried, with varying degrees of success. The most common recommendations were:

  1. Heavier concentration of AA fire.
  2. Alteration of gunsights for firing at close-in, fast-moving targets.
  3. Grouping of ships for mutual protection on picket stations.
  4. Violent evasive maneuvers by smaller, highly maneuverable ships.
  5. Continual air coverage of picket vessels.

AA Fire Kills the Most Kamikazes

Suicide planes present a special problem to AA gunners, because the pilots seldom exhibit fear of an AA barrage. Instances have been reported of kamikazes continuing their dive, although severely damaged and afire. One continued in after both wings had been shot away. Ordinarily, a direct hit, blowing up the plane in air, is sufficient to stop the attack. Effective AA fire is made difficult not only by the evasive maneuvers of the plane, but also because many of the planes have armor in vital spots and self-sealing gas tanks. Furthermore, ships usually have no more than 20 seconds to destroy planes, once they come into range.

An explosion engulfs the USS St. Lo (CVE-63), a Cassablanca-class escort carrier, after a kamikaze crashes into her flight deck. It was the first major U.S. warship sunk by a suicide attack. Image: U.S. Navy
An explosion engulfs the USS St. Lo (CVE-63), a Cassablanca-class escort carrier, after a kamikaze crashes into her flight deck. It was the first major U.S. warship sunk by a suicide attack. Image: U.S. Navy

Despite such difficulties, it has been anti-aircraft fire which accounted for the greatest number of suicide planes. A high echelon action summary after the Leyte and Lingayen operations estimated that approximately half of the planes committed to suicide missions were shot down by anti-aircraft fire before reaching their objectives. Another one-sixth, it was estimated, were destroyed by the Combat Air Patrol. Thus, about two planes in three were destroyed before reaching their target.

Antiaircraft Action Summary “Suicide Attacks” April 30, 1945

The suicide attack represents by far the most difficult anti-aircraft problem yet faced by the fleet. The psychological value of AA, which in the past has driven away a large percentage of potential attackers, is inoperative against the suicide plane. If the plane is not shot down or so severely damaged that its control is impaired, it almost inevitably will hit its target.

Flames consume the flight deck of the USS Belleau Wood (CVL-24), an Independence-class carrier, as sailors fight to control the fires started in a kamikaze attack. In the background, the USS Franklin (CV-13) also burns from a kamikaze. Image: U.S. Navy
Flames consume the flight deck of the USS Belleau Wood (CVL-24), an Independence-class carrier, as sailors fight to control the fires started in a kamikaze attack. In the background, the USS Franklin (CV-13) also burns from a kamikaze. Image: U.S. Navy

Expert aviation opinion agrees that an unhindered and undamaged plane has virtually a 100 percent chance of crashing into a ship of any size regardless of her evasive action. At the present time ships are destroying more than 50 percent of all attacking suicide planes, as compared with 33.6 percent success against dive and torpedo attacks during the first half of 1944.

Conventional attackers normally turned away in the face of a tremendous AA barrage, to live to fight another day. Suicide attackers pressed on regardless of the fire directed at them.

Summarizing, analysis of AA actions shows:

  • 1,444 suicide and non-suicide planes were taken under fire.
  • 352 suicide planes approached within gun range.
  • 40 (11 percent) of these were shot down before committing themselves to a crash attempt.
  • 312 suicide attempts were made on ships.
  • 191 (61 percent) were shot down or deflected, but of these 53 (17 percent), crashed close enough to ships to damage them.
  • 1092 non-suicide planes were taken under fire.
  • 156 (14 percent), were shot down.
  • 23 (1.2 percent), scored hits on ships.

The U.S. Navy’s AA Guns

Despite the U.S. Naval Aviation’s technological supremacy over Japanese aircraft, U.S.N. Combat Air Patrols (CAP) were simply not enough to cover the entirety of the massive invasion fleets. While large groups of kamikazes gathered to attack the vital American carriers, many suicide planes came in small groups or individual attacks. Many of the latter fell on the isolated picket destroyers and similar vessels. Their desperate gun battles with the kamikazes came down to the effectiveness of their guns, and the gun crews fighting for their lives.

5-inch/38 gun

“Without any doubt the Commanding Officer considers the 5″ gun using the Mark 53 VT projectile as the most effective weapon against suicide planes.” (Commanding Officer, Destroyer Squadron Two)

As described in the preceding U.S. Navy reports, the 5″/38 gun provided the best opportunity to destroy kamikazes at a safe distance. By almost all accounts, the U.S. Navy’s 5-inch gun, coupled with the Mark 37 Gun Fire Control System, dual-purpose naval gun of the war. When used with new “VT-fuse” shells, the 5-inch guns could create a cloud of shrapnel during barrage fire — powerful enough to tear off wings and tails of attacking aircraft.

Two 5″/38 Mark 12 dual-purpose gun mounts aboard an Essex-class carrier stands ready for action, directed by the Mark 37 Fire Control System. Image: Author’s Collection
Two 5″/38 Mark 12 dual-purpose gun mounts aboard an Essex-class carrier stands ready for action, directed by the Mark 37 Fire Control System. Image: Author’s Collection

The turret-mounted 5-inch guns had a high rate of fire, about 15 rounds per minute as a baseline. Experienced gun crews could reach up to 22 rounds per minute during critical short periods. Even the older pedestal mounted 5-inch guns could reach 12 rounds per minute in AA fire. The average barrel life for the 5-inch gun was about 4,500 rounds. The 5-inch rounds provided the U.S.N.’s most reliable “kill-stop” against aircraft.

40mm Bofors

“Accurate 40mm fire will knock down a suicider. More intensive target practice should be mandatory for all 40mm gun crews.” (Commanding Officer, Destroyer Squadron Two)

The U.S. military began license-built production of the highly effective, Swedish-designed Bofors 40mm L/60 gun during 1941. Most of the U.S. Navy’s 40mm guns were water-cooled variants of the automatic dual-purpose gun (140 rpm maximum). The 40mm guns used a 4-round ammunition clip (about 20 pounds per clip) with automatic extraction and an integrated cam-operated, recoil-powered autoloader.

Crewmen aboard the USS Hornet (CV-12) operate a 40mm Bofors anti-aircraft gun during combat in 1945. These rapid-firing guns were the Navy’s main defense against low-level suicide attacks. Image: NARA
Crewmen aboard the USS Hornet (CV-12) operate a 40mm Bofors anti-aircraft gun during combat in 1945. These rapid-firing guns were the Navy’s main defense against low-level suicide attacks. Image: NARA

Production increased steadily during the war and by 1943 the 40mm Bofors gun was the U.S. Navy’s most numerous AA gun and accounted for nearly half of all Japanese aircraft shot down by U.S. Navy AA fire during the war. After 1943, the 40mm guns became more accurate when they were coupled with the Mark 14 gunsight — which used two gyros to calculate the lead angle to the target while projecting an aiming point for the gunner. Additional accuracy was gained when the Mark 14 sight was integrated into the advanced Mark 51 Gun Director System.

U.S. Coast Guardsmen feed 4-round ammunition clips into a 40mm Bofors gun while under attack by Japanese kamikazes. Four rounds of ammo weighed about 20 pounds. Image: NARA
U.S. Coast Guardsmen feed 4-round ammunition clips into a 40mm Bofors gun while under attack by Japanese kamikazes. Four rounds of ammo weighed about 20 pounds. Image: NARA

The Navy’s 40mm guns were provided in single, double, and quadruple mounts, and they did the lion’s share of kamikaze killing, their high rate of fire and overall accuracy were indispensable. While the 40mm shells were powerful, they were not entirely reliable as a “kill-stop” munition, and the 40mm warhead was too small to be fitted with a VT proximity fuse.

20mm Oerlikon

“Although the gun may score many hits at close range, it does not destroy the plane in time to prevent a suicide crash.” (Commanding Officer, Destroyer Squadron Two)

With World War II on the horizon, and with attack aircraft rapidly growing in size and speed, U.S. Ordnance sought a replacement for the .50 caliber M2 Browning (water-cooled) AA machine gun.

A gunner aboard the USS Natoma Bay (CVE-62) mans a 20mm Oerlikon anti-aircraft cannon during Pacific operations. Image: NARA
A gunner aboard the USS Natoma Bay (CVE-62) mans a 20mm Oerlikon anti-aircraft cannon during Pacific operations. Image: NARA

The Bureau of Ordnance quickly settled on the Swiss-made 20mm Oerlikon Mark I. U.S. manufacture of the 20mm gun began in the summer of 1941, nearly 125,000 Oerlikon guns were made in America by the end of WWII. The 20mm guns were accurate and fast-firing — an experienced crew fed the gun’s 60-round drum magazines to achieve a 300 rpm cyclic rate.

Until the advent of the kamikaze, the Oerlikon guns were first-rate short range AA guns (1,000-yard effective range). However, when facing fanatical suicide aircraft, its lightweight HE shell (just 4.3 oz) was unable to provide the “kill-stop” that the U.S. Navy required. Consequently, during early 1945, the U.S. Navy replaced as many 20mm guns with the 40mm Bofors as possible.

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G.I. Ingenuity: M1 Garands Firing Mortar Shells By Tom Laemlein

American infantrymen were always looking for additional firepower, particularly the kind they could easily carry into battle. After the breakout from Normandy, U.S. infantrymen found themselves in more and more close-quarter actions, frequently clearing their German opponents from fortified positions in house-to-house fighting.

An  M1 rifle equipped with an M7 rifle grenade discharger to launch a M9A1 anti-tank grenade. England, spring 1944. Image: NARA
A soldier with an M1 Garand rifle equipped with an M7 grenade launcher demonstrates firing an M9A1 anti-tank grenade. Photographed in England during the spring of 1944. Image: NARA

Grenades, both hand and rifle launched, were well-respected and time-honored offensive weapons. But hand grenades offered a very limited range, and rifle grenades provided little punch. The 2.36-inch M1A1/M9/M9A1 Bazooka gave the G.I.s a measure of “portable artillery” with its 3.5-pound High Explosive Anti-Tank (HEAT) round that proved quite useful against German field works and machine gun nests.

However, there were never enough Bazookas available to meet the demand, their range and accuracy was poor (about 50 yards maximum), and there was little fragmentation effect from the rocket warhead.

of the 60mm mortar round on the M1 fragmentation grenade adapter. Note the adapter bodies to the right. With the 101st Airborne Division, Germany 1945. NARA
A soldier loads a 60mm mortar round on his M1 Garand equipped with a grenade adapter. Image: NARA

The G.I.s in Western Europe were looking for something more — a weapon that offered more than a grenade, but less than artillery. They found an answer with the ammunition for the M2 60mm mortar.

An Explosive Innovation

In the March 2, 1945, edition of Yank, the Army weekly magazine, reporter Sgt. Mach Morriss talked with a company commander of the 83rd Infantry Division about an effective G.I. innovation:

M1 Garand fitted with an M7 grenade launcher. USMC, Korea 1951.
A Marine holds his M1 Garand rifle that is fitted with an M7 grenade launcher during the Korean War sometime in 1951. Image: NARA

“He certainly enlightened me on one thing. He said that there were times, in house-to-house fighting particularly, when we needed a weapon somewhere between the hand grenade and the bazooka. He said the bazooka projectile would sometimes fail to explode if it hit too light an object, or if it didn’t hit solidly and then scooted along the ground. We needed a weapon to blowout doors and to shoot through windows, spraying a room with shrapnel.

“Now, the men of A Company do not claim credit for originating this idea, but they have put it into practice and say it works like a charm. They take a 60mm mortar shell and remove the increments. Then they take a hand-grenade adaptation and fit the fins of the mortar shell into the prongs on the adaptation and wire them securely together. Fired as a regular hand grenade from a rifle, this gives a flat trajectory range of approximately 135 yards and an arch range of 300 to 400 yards. The range is increased by elevating the rifle; it is also increased by putting the butt of the rifle against the floor, thereby lessening the kick.

M2 mortar 60mm shell
American troops prepare to fire a 60mm shell from an M2 mortar. The M2 fired a variety of rounds, including high explosive and white phosphorus. Image: NARA

“With this arrangement, every rifleman is a potential mortarman and A Company goes into action with three mortar shells to each squad, bringing the mortar to the very front line. When the Infantry runs out of mortar shells, they borrow from the mortar squad. This saves bazooka projectiles.

“They started using the new gadget at Mariadorf around Nov. 22, and it did a lot of work at Stavelot. ‘The Germans didn’t know what the hell they were getting there for a while,’ the CO said. ‘I assume they do now.’”

The Components

The U.S. Ordnance description of the Grenade Launcher M7 is as follows:

“The Grenade Launcher M7 is used to fire rifle grenades from the Rifle, Caliber .30 M1, using the Cartridge, Rifle Grenade, Caliber .30, M31 as the means of propulsion. The rifle with launcher attached will fire A.T. Grenades M9 and M9A1; A.T. Practice Grenades M11 and M11A1; Rifle Practice Grenade M11A2; Rifle Impact Fragmentation Grenade M17 (formerly the T2), and, when used with the Adapter M1, the Mk. II Fragmentation Grenade.

60mm round attached to M1 Garand rifle 101st Airborne Division
A 60mm mortar round fitted on an M1 fragmentation grenade adapter during World War II. Image: NARA

“The launcher is secured to the rifle by a latch -which clamps behind the bayonet lug. A stud on the launcher protrudes into the valve screw when the launcher is assembled. The launcher body has six graduations for different ranges. A grenade retainer spring slightly larger in diameter than the launcher body, serves to hold the grenade in its proper position on the launcher.

“Service ammunition may be fired from the cartridge clip when the grenade launcher is in place. Since the valve is then open, full recoil is impossible, and the rifle can only be operated as a single shot weapon. The launcher weighs 12 ounces, is 7 ½ inches long, and has a bore of ½ inch.”

The 60mm Mortar Shell

Two types of 60mm high explosive shells were used. The first was the M49A2 high explosive, using the “point detonating fuse M52B1”. The total weight of the shell was 2.73 lbs., with 0.34 lbs. of TNT filler.

The 1)	60mm mortar round with the M17 stabilizer assembly. Image: NARA
Shown here is the 60mm mortar round with the M17 stabilizer assembly attached. Image: NARA

The second was the M49A3 high explosive, using the “super-quick point detonating fuse M525”. The total weight of the shell was 3.05 lbs., with 0.34 lbs. of TNT filler.

The Mechanics

The following description of the assembly process comes from the U.S. Army ETO publication “Battle Experiences”, provided by Corporal A. Mead, Company G, 271st Infantry Regiment:

1. General: “We fire the 60mm mortar shell, high explosive, from the M1 rifle by means of the grenade launcher M-7 and an improvised adapter. We have found this device to be more accurate than wiring the mortar shell to a grenade adapter because of the increased steadiness of the shell.” 

2. Description: “The adapter consists of a metal cylinder about five inches long and open on one end so that it slips over the grenade launcher. On the closed end is a stud which fits snugly into the cartridge well of the 60mm mortar shell. Our ordnance personnel manufactured the adapters from light scrap metal.”

3. Use: “Remove the increments and cartridge from the 60mm mortar shell and insert the stud securely into the cartridge well. Place the adapter on the grenade launcher, pull the safety pin and fire. Best results are obtained from the kneeling position with the rifle butt resting on the ground. An angle of 45 degrees will give a maximum range of 125-150 yards.”

Since the modification was absolutely non-standard, and had not been tested or approved by U.S. Army command staff, the folks from the ETO Ordnance Section felt compelled to comment:

of the 60mm mortar round on the M1 fragmentation grenade adapter. Note the adapter bodies to the right. With the 101st Airborne Division, Germany 1945. NARA
A 101st Airborne Division soldier handles a 60mm mortar round. Note the rifle adapter bodies to the right. The photo was taken in Germany during 1945. Image: NARA

“Note: The Ordnance Section, European Theater of Operations, in general considers unorthodox employment of ammunition to be dangerous and recommends that this device be used only in an emergency.”

A later issue of “Battle Experiences” from the spring of 1945, carried this unattributed description of the 60mm mortar round conversion into a rifle grenade. Note the relatively high “dud-rate”.

With grenade adapter M1:

A. The 60mm mortar shell (high explosive) may be fired from the M1 rifle by means of the grenade launcher M7 and the fragmentation grenade adapter. Six inches of wire per shell and a pair of pliers are the only additional materials needed.

B. The preparation is as follows: (1) “Remove increments from mortar shell. (2) Bend outward the finger of the grenade adapter designed to receive the fragmentation grenade’s handle. (3) Insert the fins of the mortar shell into the fingers of the grenade adapter, thus securing the shell to the adapter.

C. The rifle normally is fired from the kneeling position with the butt resting on the ground. An angle of 45° will give a maximum range of 100 to 110 yards, 60° will give 85 yards range, 70° will give 60 yards range. Low angle fire can also be used and is often fired into thick hedgerow foliage to produce tree bursts. (Note: The safety pin must be pulled before firing.)

D. Due to the relatively low force exerted by the rifle grenade cartridge, the fuse will sometimes not arm and the shell will be a dud. This is especially true of low-angle fire, which will produce about 23% duds.

E. Accuracy has been improved using a sight improvised by the division ordnance company. It is attached to the stacking swivel and establishes the angle of elevation. Direction is obtained by sighting over the barrel.

U.S. Ordnance Takes Its Shot

Apparently, word had gotten back to stateside ordnance about the 60mm mortar/rifle grenade modification.

loading a 60mm mortar round on an M1 rifle
A G.I. loads a 60mm mortar round on an M1 rifle equipped with the M7 grenade launcher. Image: NARA

During the late spring of 1945, U.S. Ordnance created a publication titled “Weapons for Jungle Warfare”, and there is a listing for a (almost) standardized version of G.I. modification:

Shell 60 MM, with M17 Stabilizer Assembly: This is an assembly by which a standard rifle may be made to serve some of the purposes of the 60mm mortar. It makes use of the standard 60mm (M49 type) shell, including the super-sensitive PD fuse, M52, and the fin assembly.

The propelling charge is removed, however, and in place of it, there is screwed into the base of the shell an M17 stabilizer with a 15-grain booster charge and the hand grenade fuse. This shell assembly is fired from a rifle, preferably supported on a stock on a surface which is not extremely hard.

At an elevation of 45 degrees, a maximum range of 170 yards has been attained. It is believed, however, that this assembly would be more useful in jungle warfare when fired with a flatter trajectory and with a range of from 50 to 75 yards. This item has not been recommended due to the excessive breakage of rifle stocks in preliminary firings, especially when the rifle butt is placed on hard surfaces.

Conclusion

The last line of that sort-of catalog listing essentially ends the official discussion of the 60mm mortar round/rifle grenade modification becoming a standardized U.S. weapon.

Even so, when the G.I.s in the ETO needed an immediate solution to a firepower need, they didn’t ask permission, and they didn’t seek forgiveness. They followed their uniquely American instincts, and improvised a weapon to help bring them victory.

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