M109 is an American 155 mm tracked self-propelled howitzer used by the United States Army and by many other nations across the world.

Introduced in service with the US Army in 1963, the US M109 SpH has since been upgraded several times, the M109A6 Paladin variant currently being the main US self-propelled howitzer.

The latest variant, the M109A7 entered service starting with 2013.

The US M109 155 is a tracked heavy-armoured self-propelled howitzer with a mass of 24.5 tonnes (27.5 tons).

It has a length of 9.1 m (30 ft), a width of 3.15 m (10 ft 4 in), and a height of 3.25 m (10 ft 8 in).

M109 155 mm self-propelled howitzer has a standard crew of four (4) persons, but the crew can be made up to seven (7) people.

Usually, the crew consists of the section chief/commander, the driver, the gunner, and the ammunition handler/loader.

The crew can be expanded to a maximum of seven, including the commander, the driver, the gunner, two loaders, and two ammunition handlers.

The role of the commander or gunner is to aim the cannon left or right (deflection) and up and down (quadrant).

As main gun, M109 has a 155 mm L/39 caliber M126 howitzer and as secondary armament is equipped with a 12.7 mm (.50 caliber) M2 machine gun.

M109 155 mm SpH is powered by a 450 hp (335.56 kW) Detroit Diesel 8V71T and has a power-to-weight ratio of 18.7 hp/t.

Using a torsion bar suspension, M109 has an operational range of 350 km (216 mi) and can reach a maximum speed of 56 km/h (35 mph).