During World War II, the U.S. Army added a cannon company to each infantry regiment. Initially, these cannon companies used the M3 75MM pack howitzer. When a more powerful weapon was required, a new short 105MM barrel was married to the recoil mechanism and carriage of the M3. The resulting M3 105MM howitzer, adopted in 1942, was widely used. It was not a successful design and was retired at the end of the war.105MM Airborne HowitzerDesigned to be deployed with airborne troops, the M3 105MM howitzer is a modified version of the smaller 75MM pack howitzer. The design cannibalized the older M2 howitzer and used the barrel and split trail carriage of the 75MM pack howitzer. The original design produced for testing in 1941 was designated as the T7. It was not until 1943 that the howitzer entered production as the M3A1. This variant included a reinforced split trail design with thicker metal. The prime mover was typically a standard quarter-ton jeep.Ahead of the D-Day invasion, some divisions were equipped with the M3A1, while others retained the 75MM pack howitzer. It was not until December 1944 that the M3A1 entered full service with the Allied Forces, and only by the end of the war did it see service with all airborne divisions in Europe. Other operators of the M3 acquired them through Lend-Lease, including France and the United Kingdom.While the M3 was retired by the end of World War II by the U.S. Army, some units utilized a modified M3A2 variant during the Korean War. The last operational use was in 1951 by divisions of the Republic of Korea. The M3A2 was equipped with a small shield bracing the barrel to add protection for the fire crew.Today, M3A1 howitzers are generally used in salute batteries firing blank shells.