M109A4

The M109A4 is an American 155mm self-propelled howitzer, an upgraded variant of the M109 series. It features improved reliability, availability, maintainability (RAM) enhancements, and nuclear, biological, and chemical (NBC) protection.

Developed in the late 1980s under the Reliability, Availability, and Maintainability (RAM) program, the M109A4 was designed to modernize existing M109A2 and M109A3 chassis to extend their operational lifespan. The upgrade kits began entering service with the United States Army and National Guard in 1989, standardizing automotive and electrical components across the fleet. While the US military rapidly transitioned to the M109A6 Paladin, the A4 variant was widely exported and saw operational use with international partners, including Belgium, Canada, and Morocco. Although retired from active US inventory, the M109A4 remains in service with several foreign nations and has recently seen combat deployment in Ukraine following donations from European allies.