The M9 Armored Combat Earthmover (ACE) was first fielded in 1986, by the U.S. Army and also used by the U.S. Marine Corps. Originally manufactured by BMY Combat Systems, owned by United Defense LP and later was bought out by BAE Systems in 2005. The M9 is a highly mobile, fully tracked, air transportable, armored amphibious vehicle, capable of supporting forces in both offensive and defensive operations. It has the ability to breach berms, prepare anti-tank ditches and combat roads, remove roadblocks, prepare access routes at water obstacles, perform maintenance and repair of roads and supply routes and construction of fighting positions. The primary functions are bulldozing, rough grading, excavating, hauling and scraping, and can be used as an earth hauler, cargo carrier or prime mover, as well.

The M9 consists of welded aluminum with selected steel and aramid-laminated plates for protection. It comes equipped with 8 smoke grenade launchers, allowing the vehicle to create a smoke screen. The engine, drivetrain, and operators compartment are located in the rear of the vehicle. The front has an 8.7 cubic yd. (67 cubic m), apron and dozer blade. The Hydro-pneumatic suspension allows the front of the vehicle to be raised, lowered or tilted. It has 8 high-pressure hydraulic rotary actuators that connect to the road wheels.

The M9 uses a one-man crew, the driver, who is thoroughly trained because of the lack of visibility while operating. An armored cupola containing 8 vision blocks cover the driver's compartment. It is powered by a Cummins V903C 8-cylinder, 4-cycle 295hp diesel engine with a Clark 13.5 HR 3610-2 manual transmission. It weighs 36,000lb (16,329.32kg) and is air transportable by C-130, C-141 or C-5. It is 20ft 5in (6.22m) long, 8ft 9in (2.67m) high and 10ft 5 in (3.2m) wide. Its fuel tank can hold 134gal (507 L) of fuel and can travel up to 30mph (48.3km/h) with a cruising range of 230mi (370km).

There has been a phase improvement program implemented for the M9. The System Improvement Plan (SIP) is led by Marine Corps Systems Command and took 6 to 8 years to develop. The modernized M9 looks the same as the legacy M9 but has been overhauled. The upgrades include a redesigned hull, an improved hydraulic system, fire extinguisher system and a bigger engine. The lever operation system was replaced with joysticks and a front camera system has been added, now allowing a more improved view for the driver.