Waves of United States Marines moved toward their landing beaches on the tiny volcanic island of Iwo Jima in February 1945. Aboard their LVTs (landing vehicles, tracked), the more experienced among them hunkered down as low as they could to avoid the expected Japanese fire. Yet no defensive fire greeted the Americans as they approached Sulfur Island’s sandy black shore. Instead, the Japanese waited until the leathernecks were on the beach before letting loose with a withering fire from their well-concealed positions.
Corporal Roy Benson was a member of Company C, 2nd Armored Amphibian Battalion, which was charged with supporting the landings. He rode aboard an LVT also, but his was an LVT(A)4, equipped with an M-1A1 75mm pack howitzer in a turret, and he was the weapon’s gunner. The LVT(A)4 was designed to provide fire support to the landing forces after the naval barrage had been lifted. Benson’s vehicle, in the leading wave, was one of the first LVTs to climb up onto the shore. Unfortunately for the Marines, the fine layer of volcanic ash that covered the island prevented most of the tracked LVTs from moving forward, and they quickly bogged down. Those that could still move backed into the surf and moved along the shoreline, firing at known and suspected enemy positions. Those that could not return to the water were soon victims of Japanese fire.
The crewmen of Benson’s LVT(A)4 used their howitzer to good effect, firing at several likely targets. When the vehicle commander pointed toward some rocks above the shoreline, Benson saw a Japanese soldier holding binoculars and using a radio. He was a forward observer, directing enemy fire onto the struggling Marines. Taking careful aim, Benson fired and killed the enemy soldier with one shell from his howitzer.
Such was the accuracy of the M-1 75mm pack howitzer, one of the more unsung weapons of the war. Often overlooked because it was smaller than the better-known 105mm and 155mm cannons that equipped most Army and Marine artillery units, it was its size that enabled the pack howitzer to find a useful niche. The small gun had a mobility advantage—it could go where the larger fieldpieces could not, into jungles and mountains, where soldiers and Marines depended on it for close fire support. The M-1 was also adaptable, suitable for use on a number of vehicles and easily broken down for parachute drops. Despite its many uses, though, this highly successful artillery piece barely made it into production; it was only the demands of a global war that saved the 75mm pack howitzer from the scrapheap.
Like other armies around the world, after World War I the U.S. Army began evaluating the performance of its various branches with an eye toward being better prepared for any future conflict. To update its artillery, the Army convened the Westervelt Board. Among other things, this board was charged with designing a weapon that was 3 inches in caliber, with a range of at least 5,000 yards and light enough to be broken down into no more than four loads, portable by mules. The board set to work and developed several models of what, by 1927, became standardized as the M-1 pack howitzer.
The M-1 weighed 1,269 pounds and required at least six mules to carry it, but the new 75mm gun had an impressive range of more than 9,400 yards. It could hurl its 14-pound high-explosive shells at a maximum rate of six rounds per minute, with a sustained rate of fire of three. The tube could elevate to 45 degrees and depress to 4 degrees. That was quite an achievement for an artillery piece only 13 feet, 1 inch long, 4 feet wide and just over 3 feet high.
The new howitzer fit into the American divisional structure as well. Each division had three artillery regiments. In each of the regiments, one battalion was equipped with the new howitzer while the other two battalions operated the heavier 155mm howitzer. As impressive as the new design was, its development coincided with severe fiscal constraints that were beginning to be placed on the Army during the interwar period. Rather than receive the much anticipated new howitzer, artillery units were eventually forced to get by with the older M1897 75mm gun, large numbers of which were left over from World War I. December 7, 1941, changed all that.
With the beginning of World War II, the great need for artillery of all types did away with the financial limitations, and production increased. A newer, modernized carriage for the howitzer, designated the M-8, replaced the original M-1 carriage. The steel and wood tires of the older carriage were replaced by steel rims with rubber tires, and the split trails that opened to stabilize the gun were eliminated in favor of a nonopening box trail.
As the war progressed, the military urgently sought artillery to equip its newly forming airborne and armored divisions, and the pack howitzer came to the fore. Its compact size and low weight coupled with its ability to be quickly assembled or taken apart for transport made it ideal for lightly equipped parachute units. The retirement of horses and mules in favor of the ubiquitous jeep also eliminated many of the issues of breaking down and transporting the weapon, and it was easily adaptable to various vehicles as a self-propelled gun for mechanized units.
For airborne use, the M-1 could be loaded complete into a glider, towed by jeep or pulled by the gun crews using leather straps attached to the weapon. Airborne artillerymen spent hours in training, pulling their howitzers at the double. Disassembled, the pack howitzer could be airdropped by parachutes. Nine “paracrates” were used to prepare the weapon for airdropping at a total weight of 2,549 pounds. Some of the paracrates could be slung under the fuselage of a Douglas C-47 transport plane, while other loads were pushed out the cargo bay doors. Once on the ground, a well-trained gun crew could unpack the howitzer from its paracrates, reassemble and prepare the gun for action in seven minutes. The major drawback to dropping the guns by parachute was that if all the components couldn’t be recovered—a parachute blowing off course, or damage to the contents on landing—the entire gun was out of action.
American airborne divisions organized their parachute field artillery battalions into three firing batteries of four guns each, plus a headquarters battery. British paratroopers used the pack howitzer as well, their division having an “air-landing light regiment” for its divisional artillery component. This regiment was based on three batteries of 75mm pack howitzers replacing the 3.7- inch howitzers previously used. Each battery had six guns instead of four, and each gun section had two jeeps and three trailers for towing and ammunition hauling. The regiment was rounded out with two additional batteries of antitank guns and one of light anti-aircraft guns. British airborne troops found the glider to be the most suitable way to transport their artillery.
Paratrooper John McKenzie served in the 456th Parachute Field Artillery Battalion, 82nd Airborne Division. He later wrote of his experience with this pack howitzer–equipped unit. The 456th entered combat in Normandy, arriving by ship a few days after the airborne landings. McKenzie recalled the fighting there, and the work emplacing the guns. The howitzers’ exact location had to be known to the fire direction centers so they could accurately calculate firing data for the guns, to enable them to put precise fire on the targets spotted by the observers. Survey teams would determine the location a battery was to occupy. The howitzers would be dug in, placed in firing pits to protect them from German counterbattery fire. Once located by the enemy, the guns would often have to be moved to a new site. The 456th had to move its guns 25 times during its 33 days of combat in Normandy.
McKenzie continued with the unit through to the American counterattack in the Ardennes in January 1945. The German offensive had run out of steam, and the 82nd was part of the effort to harass their retreat. McKenzie was one of a team of forward observers assigned to a battalion of the 505th Parachute Infantry Regiment. On one occasion, his group took up a position overlooking the village of Vielsalm. Suddenly a German column approached the town, some 500 troops in halftracks and trucks. The observers prepared a fire mission for the guns of an entire battalion. The subsequent barrage landed as the Germans were at a crossroads, disabling some of the vehicles and blocking the route. Mortar fire then landed at the head of the enemy convoy, stopping it. This left the Germans vulnerable to an ambush by American infantry. In a short time, it was over; almost all the German force lay dead, wounded or captured. The action outside of Vielsalm was just one incident demonstrating that if used in combination with other weapons, the small howitzer could be just as lethal as its larger brethren.
Pack howitzers also proved effective when used by armored and mechanized forces. The gun’s small size meant that it could be easily fitted into the armored vehicles in production at the start of the war. The first vehicle to be so adapted was the T-30 halftrack, which was essentially a modified M-3 that mounted the howitzer in the passenger compartment. Never standardized, 500 of the modified M-3s were used until a proper replacement could be produced for the new medium tank battalions.
Thanks to the gun’s effectiveness, the replacement was armed with the small howitzer as well. The M-8 howitzer motor carriage was based on the chassis of the M-5 Stuart light tank. In place of the M-5’s 37mm gun turret, the M-8 mounted a 75mm pack howitzer in a larger, open-topped turret. While by no means heavily armored, it gave better protection to the crew than a halftrack. In all, 1,778 were built, and they saw extensive service in armored cavalry units. French armored units supplied by the Americans were also equipped with 174 of them.
Not to be outdone, the Marines also found a use for the versatile little gun. Faced with the hazards of opposed landings, the tracked LVT was modified as a gun platform. Designated the LVT(A)1, the hybrid landing vehicle was fitted with a turret from the M-5 Stuart. When the landing forces needed even more firepower, it was only natural to fit the M-8’s 75mm turret to an LVT. This became the LVT(A)4. Its main purpose was to provide support between the time naval gunfire lifted and artillery units came ashore and were ready to fire.
There were two theaters of operation where the M-1 howitzer was transported as originally intended—on the back of a mule. In Italy, the mountainous terrain precluded towing the guns with jeeps or trucks, and mules were called back into service. The four-legged wonders were used to carry guns as well as general cargo and casualties. The 10th Mountain Division’s artillery was equipped with pack howitzers in four battalions, each with 12 howitzers and a veterinary section to provide care for the animals that supported the battery. Besides the six mules that carried the gun itself, five more were needed to haul ammunition and one to carry tools and other equipment.
The other battlefront where mule skinners brought the compact howitzer into play was the China-Burma-India Theater. Here the 5307th Composite Unit (Provisional), the famed “Merrill’s Marauders,” used two pack howitzers to provide close fire support in April 1944. The unit’s namesake, Brig. Gen. Frank Dow Merrill, requested the two guns be flown to the unit at Hsamsingyang, Burma. Gun crews were formed from men who had previously served in pack artillery units. Both guns were dropped by parachute and were in action within two hours. They proved popular with the troops and soon gained the nickname “the fatboys.”
The two pack howitzers were used in a direct fire role during the fighting in Burma, rather than the traditional indirect fire method of arcing rounds onto a target from beyond visual range. Often the guns were aimed directly at targets within sight. Radio transcripts convey the usefulness of these guns. During the Hsamsingyang fighting, the guns fired at pillboxes in the Japanese lines, scoring a direct hit on one and forcing the enemy out of another. The guns also proved useful against machine gun nests. When a lieutenant saw strong Japanese positions on a hill and began to take fire, he called for the pack howitzers, saying, “Japs are in strength on the next hill…put some fatboys on the hill for us.” Men fighting on the front lines called for the pack howitzers over and over during the battle, depending on their power and accuracy to both support their attacks and defend their positions.
The M-1 pack howitzer was useful on all fronts despite its relatively small caliber. It is still in service today as the M-120 saluting gun, used at military ceremonies with blank ammunition—a final salute in itself to a proven and tested design.
Originally published in the March 2006 issue of World War II. To subscribe, click here.
