World War 2 gave rise to the airborne trooper - light infantry airdropped into enemy territory for the purpose of lightning-quick assaults or to capture key points all the while bypassing entrenched enemy defenses - and quickly proved their value. While initially utilized operationally by the Italians and Soviets, it was the German Army that so effectively utilized this weapon to great effect in the opening campaigns of the war and other nations soon followed in developing these multi-faceted elite combat units. By 1941, American military doctrine incorporated the "paratrooper" as a standard portion of its airborne force - soldiers trained in the fine art of "jumping out of perfectly good airplanes".
One of the key limitations of this type of soldier was the requirement that they be lightly armed for the jump ahead. As internal space aboard transport aircraft of the time was limited and, more importantly, the soldier could only carry so much equipment into battle, there still lay the challenge of properly outfitting these elements to make for a more capable fighting force. Many projects were undertaken for just that and one such solution for the American Army became the "105mm Howitzer M3".
The engineers went to work on the new weapon in 1941 under the designation of "T7". The design of the weapon essentially centered on shortening the existing standard 105mm howitzer gun barrel of the M2A1 howitzer - the standard light howitzer of the United States Army at the time - by some 27 inches and mating it with the existing gun carriage of the Army's 75mm Pack Howitzer. The carriage was slightly revised for the new "air portable" role though the recoil assembly of the 75mm system was retained. The result was a relatively light-weight field artillery system with the proven hitting firepower of the American 105mm. A prototype model was made available for evaluation in March of 1942 to which testing then ensued at the fabled Aberdeen Proving Ground in Maryland before being formally adopted into US Army service under the long designation of "105mm Howitzer M3 on Carriage M3". Production began in February of 1943 and would last until the end of the war in 1945.
The M3 was issued to airborne detachments as well as regular infantry within time and these were quickly appreciated for their mobility. In practice, the system proved its worth to airborne elements through effectiveness, reliability and accuracy out to 8,300 yards, utilized in dislodging enemies or covering offensive actions. The 105mm high-explosive 30lb shell had a devastating psychological effect to anyone unfortunate enough to be on the receiving end - cover or no cover and, with its split trail system, the M3 could be hitched to a mover vehicle and transported at speed. Otherwise, it was up to the gunnery crew of five personnel to relocate the system on foot. The M3 sat atop two rubber tires which made traveling short distances somewhat easy.
The M3 fired the 105x372R 105mm projectile from a horizontal breech block mechanism. The recoil system was a hydropneumatic action. Elevation spanned from -9 to +30 degrees with traverse being 45 degrees (manual rotation of the entire system left or right required beyond that figure). A trained and experienced crew could fire four rounds-per-minute and sustain fire at two rounds-per-minute as needed. Muzzle velocity was rated at 1,020 feet per second. An improved gun mount (T10) later appeared with 65-degree elevation and, thusly, increased operational range.
While the standard shell was high-explosive in nature (HE M1), the M3 could also fire the M67 High-Explosive Anti-Tank (HEAT) shell as well as smoke shells. A drill cartridge and blank shell were used for non-combat roles. The ammunition utilized by the M3 series was similar to that as featured in the M2 howitzer though with a lower-powered charge being used for faster burning of the propellant.
Over the course of its operational service, the M3 utilized various carriage types. The M3 was the basic initial production carriage and essentially a modified form of the one as used in the 75mm field howitzer. The M3A1 then followed and this version was given reinforced trail legs for the rigors of the battlefield. The final carriage variant became the M3A2 and it was this version that fitted a small blast shield for limited protection to the gunnery crew from shell splinters and artillery spray.
Operational use of the M3 began in 1943 to which 1,965 units were delivered that year. Production trailed off considerably in 1944 and 1945 with 410 and 205 units produced respectively. In all, 2,580 M3 systems were delivered to the United States Army while some were made available to French forces and South American allies.