The 75mm pack howitzer was one of the most versatile artillery weapons of the Second World War. It served in almost every campaign that Marines fought in and was nicknamed "Little Dynamite," because of its size and ability to deliver a high volume of fire. Marine artillerymen employed this weapon under conditions that made use of heavier artillery pieces either impractical, or simply impossible.
Beginning in 1920, the US Army worked to develop a 75mm artillery piece for pack transport, animal draft, and low-speed towing. The weapon was standardized in 1927 as the M1 pack howitzer. Minor changes were made to the M1 and it was subsequently redesignated as the M1A1. The piece originally was mounted on the M1 carriage, which had wood wheels and steel tires. Shortly before the start of World War II, this carriage was replaced by the M8 airborne carriage, which had modern steel rims and pneumatic tires.
In 1931 the Marine Corps took delivery of four 75mm pack howitzers. These weapons were assigned to the First Battalion, 10th Marines, then assigned to Marine Corps Base, Quantico. During the lean years of the Great Depression, only a limited budget was available for new weapon acquisitions. As a result, in the following two years The Marine Corps only had enough funds to purchase four additional pack howitzers. Though the 1930s, more of these were acquired as the Marine Corps sought to modernize its artillery force.
During the 1930s, Marine planners conceptualized a war in the Pacific and the Corps' role in this conflict. Central to this planning was the artillery's place in an assault landing force. As a lightweight, man-portable weapon, the pack howitzer played an important role in this thought process, and in its practical application. The howitzer and its crew had three primary missions in the landing force. They were; 1) reducing enemy strongpoints, 2) neutralizing enemy artillery and machine gun fire, and 3) stemming counterattacks.
As the Marine Corps went beyond the planning stages into combat exercises, pack howitzers were used in the fleet landing exercises that took place during the years leading up to 1941. Working with a variety of lighters, boats and experimental craft, Marine artillerymen practiced and honed their skills at getting their pieces onto the beach. They learned that artillery could not replace naval gunfire during the initial stages of the assault, but that artillery must be landed soon after the first waves of infantry were ashore. Also, the concept of direct support, in which the artillery worked directly for the infantry, became an important part of the way the guns were used. All of this would pay huge dividends in the Pacific war.
Throughout the war, the pack howitzer battery was equipped with four guns. Crew drill in training helped crews to perfect their skills. The diagram at left, extracted from FM 6-78, shows the pack howitzer crew formed for action. The crew was called a section and was commanded by a sergeant, titled the section chief. He was responsible for all actions by his Marines, all commands executed, and safety.
The gunner, a corporal, depicted by the "G", set the sight, deflection and elevation. All other section members were non-rated Marines. The assistant gunner, depicted by the 1 in this diagram, opened and closed the breech and fired the piece. Number 2 acted as the loader. Number 3 operated the fuze setter and set fuzes. Number 4 held rounds for number 3 to set fuzes, passed rounds to the assistant gunner for loading, and assisted number 5 in preparing charges. Number 5 prepared ammunition and shifted the trails.
Other Marines could be assigned or attached to the section. Chief among these was the driver. In most Marine units, the section had a jeep to tow the piece. But these vehicles were not used in all operations and sometimes the driver assisted with portage of the piece.
The 75mm pack howitzer was employed by either one of two methods of fire. It could be laid for direct firing against targets like tanks, bunkers, or pill boxes, typically out to a maximum effective range of 400-700 yards. In this technique of fire, the gunner centered the traversing wheel, and set the sight to the estimated range. Traversing was accomplished by moving the trail left or right to shift the entire weapon to bring it on line. This was known as "the one man, one sight" method of fire.
Using indirect lay, the section could engage targets out to a maximum range of about 9,000 yards. Typically firing as part of the artillery battery, the 75mm was used for neutralization, or harassing fires against troop concentrations, enemy defensive positions, and other targets. Forward observers called and adjusted fire for the battery and the fire direction center turned this information into deflection and elevation for the pieces. There were three basic types of missions using indirect fire: grid, polar, and shift from a known point.
Once the battery was set in position, an important task was to register targets. This was accomplished by firing registration rounds onto specific targets and then recording the information onto a range card. The targets were then assigned a reference number, identified, for example, as "concentration A11," etc. Especially at night, this information was frequently used to quickly lay the pieces on target to impede and break-up Japanese banzai attacks.
From the first assault landing of the war at Guadalcanal, right up through the climactic fight for Okinawa, 75mm pack howitzers delivered yeoman service. They were often brought ashore under fire before the beach heads were secured to provide much-needed artillery support for the infantry Marines. For example, in November 1943 during the heavy fighting on Tarawa, the 1st Battalion, 10th Marines, equipped with pack howitzers, was attached to the Second Marine Regiment. Under command of LtCol Presley Rixey, USMC, 1/10's artillery Marines were forced to drag their pieces ashore after a hazardous approach across Tarawa's exposed lagoon.
Under heavy Japanese fire of all calibers, the artillerymen set-up a composite battery of five guns on the evening of D-Day, 20 November 1943. Getting these guns ashore was a trial by fire as the crews carried them broken down through waist deep water and over the exposed pier between Red Beaches 1 and 2. With a battery frontage of only fifty yards, these Marines were subjected to constant sniper and machine gun fire. They used their packs to knock out two Japanese bunkers by direct fire. early in the morning of D+1. The machine guns in these bunkers had been tearing through the exposed ranks of the Eighth Marines who were wading toward the beach head through chest deep water.
By the evening of D+1, the entire complement of 1/10's pieces was ashore and deployed into a battalion firing positions. During the night of D+2, the battalion fired over 1,200 rounds in support of the Sixth Marines against massed enemy banzai charges. These concentrations were instrumental in stopping the attacks. One of the battalion's forward observers, 1stLt Norman Milner, later received a Silver Star for his gallantry in action. LtCol Rixey also received a Silver Star for his courageous actions on Tarawa. Amazingly, 1/10 suffered only minor casualties during one of the fiercest fights in Marine Corps history; seven Marines killed and eighteen wounded.
During the campaign in the South and Central Pacific, Marines appreciated the strengths of the little pack howitzer, but also recognized that the weapon had limitations. Against increasingly strong enemy fortifications, the 105mm howitzer was recognized as a weapon that had more versatility and firepower. But the larger gun never fully replaced the pack howitzer and some Marine divisions still maintained pack howitzer battalions right up through VJ-Day.
Finally, after the end of the war, the pack howitzer was withdrawn from frontline service. But many still can be seen today as memorials in parks and as salute guns on military bases around the country. The pack howitzer was a unique weapon in American service and answered the call of duty for the Marines of World War II.
Field Manual 6-78, 75mm Pack Howitzer, U. S. Army
"Little Dynamite", article, The Marine Corps Gazette, by Capt Thomas N. Greene, March 1949.
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