The 105 mm Model 56 Pack Howitzer was developed by the Italian Army and produced by Oto Melara in the mid-1950s and entered production in 1957. Since then over 2,500 have been built and sales have been made to more than 30 countries.

The advantage of the Oto Melara Model 56 is that it can be dismantled into 11 subassemblies for transport across rough terrain, lifted by helicopters such as the Bell UH-1 and its profile can be lowered for anti-tank use.

Early in 1997, it was revealed that China North Industries Corporation (NORINCO) had built a weapon almost identical to the Oto Melara 105 mm Model 56 Pack Howitzer and details of this are available in a separate entry. Some sources have stated that Mexico has taken delivery of some NORINCO versions. Ammunition for the Oto Melara 105 mm Model 56 Pack Howitzer is available from many sources and is the same as that used in the US M101 towed howitzer.

The 105 mm barrel assembly of the Model 56 Pack Howitzer is composed of the barrel, breech ring, slipper and muzzle brake. The weapon has a multibaffle muzzle brake. The vertical sliding breech block has a percussion firing mechanism which can be cocked automatically or by hand. Firing is either by hand lever or by lanyard.

The gun carriage comprises the undercarriage, saddle, cradle, upper and lower recoil systems, two balancing springs, two sights and the shield. The undercarriage consists of a cross head housing the saddle centre pivot pin, two stub-axles, spring equalising rocker arm and two articulated arms. Each of the stub-axle supporting arms has two bearings into which the stub-axle can be fitted, this carries the wheel assembly and its handbrake. Each of the articulating brackets carries a trail leg of two or three sections, which can be folded up and interlocked. The end section of the trail may be anchored to the ground by a knife or rock spade.

The saddle, with its centre pivot mounting, is provided with two side members with rear-mounted lugs that carry the elevating and traversing gear. The recoil system is contained in two cradles, upper and lower, which slide on top of each other. The upper cradle contains the two recuperator-buffers and the lower cradle contains one buffer and two recuperators. The two balancing springs have helical springs operating in sliding sleeves and the cradle is mounted on two trunnion bearings.

The sighting equipment consists of an indirect sight on the left and an anti-tank direct sight on the right. The splinter-proof shield mounted on the saddle is in two halves, both of which can be removed to lighten the weapon.

As a field weapon the 105 mm Pack Howitzer wheels are overslung and the barrel has an elevation of +65°, a depression of -5° and a traverse of 18° left and right. As an anti-tank weapon the wheels are underslung and the barrel has an elevation of +25°, a depression of -5° and a traverse of 28° left and right. When deployed in the anti-tank role it has a lower profile and increased traverse arc.

The weapon can be dismantled into 11 subassemblies, the heaviest of which weighs 122 kg, in 3 minutes and can be reassembled in 4 minutes.

The 105 mm Pack Howitzer fires the same range of ammunition as the US 105 mm M101; HE (M1) with the complete round weighing 21.06 kg, a muzzle velocity of 472 m/s and the fixed High-Explosive Anti-Tank (HEAT) (M67) round, which weighs 16.7 kg, has a muzzle velocity of 387 m/s and will penetrate 102 mm of conventional steel armour.