M109 howitzer

The M109 is an American 155 millimetre turreted self-propelled howitzer, introduced in the early 1960s to replace the M44 and M52 and still the most common Western indirect-fire support weapon of armoured and mechanised brigades. A crew of four serves it: the section chief, the driver, the gunner and the ammunition handler. It first saw combat in Vietnam, where the early vehicles suffered a fleet-wide mechanical fault and were recalled in 1967 before the improved M109A1 appeared. Later marks include the A6 known as the Paladin, which added an inertial navigation system, digital communications and automated fire control, and the A7. The original vehicle was powered by a Detroit Diesel 8V71T eight-cylinder turbocharged diesel. Its development is credited to the Ground System Division of United Defense, which later became BAE Systems Platforms and Services, and BAE Systems in York, Pennsylvania has delivered upgraded M109A5+ vehicles to Chile and Brazil. Other armies have licence-built or replaced it, among them South Korea's K55 and the British AS-90.