The USMC Expeditionary Fire Support System (EFSS)

In February of 2011, the USMC Expeditionary Fire Support System was employed in combat in support of Battalion Landing Team 3/8 (26th MEU) in Helmand Province, Afghanistan.   The combat deployment was more than a decade in the making, the culmination of development which began in the late 1990s.  The requirement EFSS was intended to fill goes back at least another decade, to the final retirement of the venerable M101A1 105mm Light Howitzer from the USMC inventory, a cannon that had first entered service before World War II.

Concept of Employment

EFSS, along with the HIMARS rocket system and the M777A1 155mm Towed Howitzer, is intended to be part of the “triad” of ground fire support systems for the United States Marine Corps.   EFSS is conceived to be a part of the assault echelon of ship-to-shore movement, and provide maneuver forces with close ground fires until tube artillery comes ashore in the on-call waves, perhaps as much as 24-48 hours after H-hour.

The EFSS is being fielded in the Artillery Regiment of the Marine Division, which is a bit of a paradigm shift from more recent previous heavy mortar efforts by the USMC, but not unprecedented, as will be discussed below.

System Components

The EFSS is built around the RT120/M327 rifled 120mm mortar.    The mortar, carriage, and baseplate weigh 1,780 pounds, and has a crew of four.  Range with standard munitions is 8.5km.  GPS-guided Precision Extended Range Munitions (PERM) are capable of ranges of 17km, with a reported circular error probable (CEP) of 20m.  Projectiles vary in weight from approximately 36 to 42 lbs.

The prime mover for the RT120 is the Growler Internally Transportable Vehicle (ITV), based on a modified M151 Jeep concept, but with a sophisticated variable suspension system and dimensions tailored for internal transport, as the name implies, in the V-22 Osprey.  The Growler has a four-cylinder turbocharged diesel engine that generates 180 horsepower, is equipped with four-wheel drive (with a selection for rear-wheel drive only), and is capable of towing 2,000 pounds cross country.

The EFSS consists of the above-mentioned mortar, two ITVs, with each respectively towing the mortar tube, and an ammunition trailer which has a bustle rack for 36 ready rounds.  Tactical and vertical mobility have been emphasized, in order to ensure equal mobility to the maneuver force being supported.


The EFSS has not been without controversy.  Much of it surrounds the Growler prime mover, which has been specifically designed to fit into the very restricted internal cargo area of the V-22 Osprey.    The cost per unit is estimated to be over $200,000.   With a narrow wheelbase and limited ground clearance, true cross country capability is in question.   The vehicle is prone to rolling in turns, and may have trouble navigating the rugged terrain in undeveloped areas in which employment is possible.   Additionally, the Growler offers no ballistic protection for its crew.  Open on three sides, it is vulnerable to small arms, fragmentation, and the IED threats that have become so familiar in the last decade.   All valid criticisms, and requiring of the assumption of significant risk in employment.

For my part, the EFSS is at best a hybrid and therefore suboptimal solution.  This is not the first foray for the Marine Corps into the idea that a heavy mortar might replace a light howitzer capability.  In the early 1960s, the M30 4.2-in (107mm) chemical mortar was mounted on a surplus 75mm pack howitzer carriage, and mated with a recoil system to ease emplacement and increase range.

The M98 Howtar*** was the result, and was briefly fielded in Vietnam with Marine Artillery units.  However, with its still limited range when compared to the howitzer, and with similar mobility requirements, the M98 proved significantly less suitable than the 105mm howitzers already in service, and not a substantial upgrade from the standard “four-deuce” in service with Marine Infantry units.

The EFSS has similar limitations.

First, the weapon is a mortar, and incapable of low-angle fire or direct fire.   High angle fire is a significant challenge in fire support coordination with fixed and rotary wing air assets that comprise fully half  of the USMC combined-arms team and will be of critical importance in supporting operations ashore before tube artillery and HIMARS can be landed.

Second, unless the preponderance of ammunition is of the PERM variety, which is a doubtful proposition due to costs, EFSS has limitations in range (8.5km)  that require it to be well inside the range fans of a host of threat weapons systems in order to successfully prosecute targets.

Third, the rate of fire of the RT120/M327 is around 6 to 8 rounds per minute, relatively low for a mortar system, which limits the volume and weight of fire that EFSS can provide.

A more appropriate solution to light and mobile fire support would seem to be that of a lightweight 105mm howitzer, using similar weight-saving materials (titanium) and designs that allowed the M777A1 155mm towed howitzer to weigh slightly over half (8,800 lbs) what the M198 155mm (15,780 lbs) system tipped the scales at.    A 105mm howitzer weighing 3,000-3,500 pounds, capable of firing more lethal and extended range modern munitions, equipped with course-correcting fuses, would be a great enhancement to the Landing Force Commander, providing a much more robust and capable fire support system for minimal additional logistic and mobility requirements.

That said, the EFSS is infinitely better as a fire support system than what existed for that niche previously, which was nothing.   It is a recognition that, despite our recent low-intensity conflict/COIN experience, the modern battlefield will see an increased emphasis on ground fires.  This  is already true of those areas in the littoral where our adversaries are building Anti-Access/Access Denial (A2AD) capabilities with an eye towards thwarting US power projection options.

(***Note, the above photo of the M98 Howtar was taken on the quarterdeck of 10th Marines HQ at Camp Lejeune.   The Notre Dame Leprechaun is undoubtedly the work of Col Chris Mayette USMC, who commanded the regiment at the time the picture was taken.   There is no substantiation to the rumor that the Howtar disappeared when he turned over command, or that a similar one now adorns his living room in his current location…)

4 thoughts on “The USMC Expeditionary Fire Support System (EFSS)”

  1. Maybe call it the “Mighty Mac”….hey wasn’t there one of those way back when?? Sure resembles one.

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