The US Marine Corps documented a requirement around 2001 for a lightweight fire support system that could be carried internally in the MV-22 Osprey hybrid VTOL aircraft. The requirement was known as the Expeditionary Fire Support System (EFSS) and the initial concept called for a fully-automated magazine-fed heavy mortar, with associated fire-control and transport vehicles.

The resultant system, known as Dragon Fire, proved heavy, complex and expensive. Following a review, the Marines recast the programme into a simple towed 120 mm mortar, rifled to give good range performance, with an electronic fire-control system and a family of light wheeled vehicles, to be known as the Internally Transportable Vehicle (ITV).

Following a two-way competition the Marine Corps Systems Command awarded the contract to General Dynamics Ordnance and Tactical Systems (GD-OTS). The ordnance portion of their proposal was the 120 mm MO 120 RT from TDA Armements of France, which has been designated the M327 for US use.

The Marines' procurement objective is 66 EFSS, plus four developmental models, along with 700 ITVs. As of May 2009 the procurement of the EFSS ordnance (M327 and associated trailer and fire-control) was:The EFSS units are issued to Marine artillery units for one-for-one replacement of the heavy M777 howitzers for aerial insertion missions. Once land link-up is accomplished the howitzers would be brought in and the mortars withdrawn again. The first set of EFSS, including the vehicles, achieved initial operational capability with the 1st Battalion, 10th Marines in March 2009.GD-OTS buys the MO 120 RT. First deployment in Afghanistan was in april 2011.