USMC Amphibious Combat Vehicle: The Dangerous Consequences of Safe Bets

As of late 2023, the United States Marine Corps is in the process of fielding the new amphibious combat vehicle (ACV). The ACV is the troubled product of both the cancellation of the Advanced Amphibious Assault Vehicle (AAAV) / Expeditionary Fighting Vehicle (EFV) program as well as the DoD’s overdue pivot towards conventional warfare preparedness. In an era during which even the last USMC Commandant has declared the death of amphibious assaults, the Corps has suddenly done an about face and fielded a new ship-to-shore fighting vehicle envisioned to have all the attributes of the canceled AAAV/EFV program: increased protection, high water speed, a 30mm cannon, and cross-country mobility equal to or greater than the M1 Abrams.

The USMC has broken these difficult to achieve requirements into separate tranches of ACV development. The ACV currently being fielded is version 1.1 which meets only two of the next-generation requirements: increased protection and mobility. ACV 1.1 is currently experiencing all the normal teething problems associated with large defense equipment acquisitions programs. Most recently, the Marine Corps and BAE systems identified that water may be seeping into the powertrain, amongst other issues. This problem will almost certainly be fixed, but is quite frustrating considering the ACV is just a modified Iveco SuperAV, an Italian amphibious vehicle designed in the 2000s. Issues like water penetrating the engine compartment of an amphibious vehicle should have been solved long ago.

An Amphibious Combat Vehicle (ACV) with the 3d Assault Amphibian Battalion, 1st Marine Division, prepares to approach the well deck of amphibious assault ship USS Makin Island (LHD 8), July 11, 2022. (MC2 Kristopher Haley/U.S. Navy)

These problems would be easier to understand in an ambitious evolutionary program like the Osprey tilt-rotor, which dramatically increased the operational reach of Marine forces. However, the ACV is neither evolutionary nor revolutionary. It is meant to be a warmed over upgrade of an existing program; a safe bet.

This safe bet philosophy gets to the core of the entire issue with the ACV concept. The program is too far gone and the Corps needs immediate replacements for the aging Amphibious Assault Vehicle (AAV) fleet. However the entire ACV concept (not program) needs a critical revaluation. Though it is in the Marine Corps’ portfolio, it is in some ways a platform of national importance. Much like the Air Force’s bombers, the Marine Corps is the only service to field a capability in this niche - a vehicle designed to swim onto hostile shores and fight like a tank in some of the worst conditions a ground force could fight in - water, tides, high waves/high sea states, reefs, shoals, sea and land mines, heavily defended beaches loaded with obstacles, and God knows whatever terrain lies behind the beachhead. 

Due to the safe bet philosophy, the ACV swims no faster than the legacy AAV, making it quite literally half as fast as the People’s Liberation Army ZBD/ZTD Type 05 series. This limits the ACV’s range, forcing the US Navy to expose itself to more danger than the PLA Navy. This range factor also limits the island to island assault capacity of the platform. Finally, slow water speed obviously makes the Marines aboard sitting ducks, especially to opponent organic precision fires.

Legacy USMC AAVs conducting welldeck operations within the US Navy’s USS San Antonio LPD-17, the lead ship of her class.

The ACV also carries less troops, with space for 13 Marines while the old AAV is capable of carrying 21. This means a standard Marine rifle company requires a more than 50% increase of vehicles to carry it from ship to shore (from 22 to 35 vehicles). This is good for disaggregating and spreading risk across the assault force, but terrible from a logistics footprint perspective. 

The most salient impact is the effect upon the amphibious shipping cube. The ACV is roughly the same size as the original AAV (both 7.9 meters in length and 3 meters in width for the ACV, 3.3 meters in width for the AAV). A US Navy San Antonio class LPD (landing platform dock) amphibious assault ship is capable of carrying 14 AAVs but is likely capable of carrying 32 AAVs when packed to the gills. This means that US Navy LPDs, warships that cost on average $1.6b, go from being able to land about 672 Marines in one wave (4.3 companies) to about 416 (2.4 companies). This significant reduction in boots on the ground per echelon does not bode well.

The interior configuration of the San-Antonio class LPD

To scale the example up, a typical Amphibious Ready Group (ARG) is usually comprised of one large amphibious warship (We’ll assume a Wasp class LHD Landing Helicopter Dock with room for 40+21 AAVs), one LPD (the San-Antonio class discussed above with likely room for 32 AAVs), and one LSD (Landing Ship Dock, a large shallow draft vessel with cranes and plenty of room for 36 AAVs). This gives a theoretical ARG space for about 129 AAVs, which we will round to 130. 

An ARG loaded with the old AAVs can theoretically land 2,730 Marines in one wave. An ARG with the new ACV would only be capable of landing 1,690 Marines, about 60% of the legacy force. This means the Corps hits the beach at almost half weight. 

Compounding the loss in numbers is a commensurate loss in firepower. Due to the safe bet philosophy, the ACV still lacks truly heavy weapons or tank-like firepower. The original AAAV/EFV concept was supposed to have a 30mm cannon, but the decision was made to axe that requirement. Even the ACV’s PLA counterpart packs a 30mm cannon (and that is just the light version). The USMC is attempting to remedy the absolute lack of heavy weapons with the ACV-30 test vehicle scheduled for 2024. Hopefully, this system will be added to the ACV 1.2 baseline.

ACV-30 test vehicle

A positive development is the stabilized remote weapons station, able to fire accurately at targets whether the vehicle is swimming or on land. However, the original AAV carried both a Mk19 grenade launcher and a .50 cal machine gun in its upgunned weapons station. The ACV’s current remote weapons station setup carries only a .50 or a Mk19, not both. To make matters worse, the remote weapon station is one of the most troublesome parts of the vehicle, and in some tests is the source of the largest number of operational mission failures.

While Vermilion is confident that the platform issues, cannon fielding, and weapons station reliability issues will eventually be resolved, the current lack of a dual-weapon setup means that a typical assault amphibian battalion now hits the beach much lighter than than the previous AAV-equipped battalion. Each AAV company is equipped with about 40 vehicles for a total of 80 weapons systems, half machine guns and half grenade launchers. An ACV-equipped amphibian company would likely bring 40 weapons systems to bear, 20 heavy machine guns and 20 grenade launchers, albeit at a higher level of accuracy. This means that the new Marine first echelon landing force comes ashore with about 40% less infantry and 50% less vehicle weapons. Hopefully those remote weapons stations function in the littoral environment.

While the Marine Corps’ semi-official position is that the extra crew protection of the ACV makes some of these trade offs worth it, this is not true when considering the pacing threat. While the exact specifications are a secret, the front glacis of the ACV is likely only effective against certain medium-caliber direct fire weapons. It is hard to see how a 35-ton vehicle designed to swim could achieve anything greater. The ACV also features a V-shaped hull designed for protection against IEDs and mines. These are welcome improvements for personnel protection, but the truth is that these protection requirements are only highly effective for the Afghanistan/Iraq counterinsurgency fight. The ACV is not currently capable of defending against rocket, missile, or tank gun rounds, all very common in the PLA inventory. 

The added protection has to be balanced against the fact that the front glacis adds significant weight to the ACV, reducing speed, seaworthiness, and troop carrying capacity. The V-hull also has a significant impact on drag in the water, slowing down the vehicle while swimming. Traveling slowly in a combat environment can be just as deadly as being lightly armored. Additionally, a nation-state is able to produce mines that outclass light amphibious vehicle armor far more easily and consistently than a counterinsurgency home-brewing explosives of variable size and often questionable reliability.

The ACV program is full of fuzzy thinking which muddies together the requirements for two totally different types of vehicles. The Corps’ priority should be on seizing the beachhead in the first place, and the focus should be on a vehicle that performs well at amphibious maneuver. Instead, the capability documents for the ACV dictate that the vehicle’s performance shall be judged 80% on the land. How does it make any sense to evaluate an amphibious vehicle using an almost entirely ground-based metric? Marine planners are far too confident that the amphibious assault will be successful and have concerned themselves with the breakout before getting the beach assault right.

The decision to choose a wheeled and not tracked vehicle is also highly questionable. Wheels may have landward mobility advantages once forces leave the beach, but that again assumes lodgment is already secure. Tracks have historically been a huge advantage for amphibious forces. Track’s advantage has nothing to do with landward movement, road movement, traction on sand, or anything related to the land. Tracks are necessary because of the nature of ocean tides and underwater hydrography. 

History abounds with examples. In July of 1943, 2nd Marine Division began planning for the invasion of Tarawa. The atoll/island is fringed by a reef, meaning that depending on the tide, the three foot minimum clearance for the Higgins boat landing craft could not be guaranteed. Lt Col David Shoup, then 2nd MARDIV’s operations officer, planned for an LTV-1 amphibious tractor-borne assault.

At around 0900 on 20 November, the naval bombardment of Tarawa (Betitu/Betio Island) lifted. However, the tide did not rise as expected for the next two days. 2nd Mar Div was forced to rely on LtCol Shoup’s LVT-1 alligator landing force for assaults on to the northern Red Beach landing zones, the LVT-1s alternating between swimming and crawling over the natural reef obstacles with their tracks. This caught the Japanese defenders by surprise, who assumed that portion of the island was not amphibiously traversable due to the reef.

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An LVT-2 Doodlebug ramming its ramp into a coral wall during testing on Saipan

A second great example is the attack on Tinian. The island is surrounded by high coral cliffs about 10-15 feet high. The natural landing beaches are far too canalized to act as effective maneuver corridors, so the V Amphibious Corps turned to amphibious tractors to make the landing a reality. Navy Seabees constructed giant hook-crowned ramps and installed them on top of LVT-2 amphibious tractors. The LVTs once again negotiated the perilous waters through a mix of swimming and use of tracks to crawl over the jagged coral reef. Once the LVTs reached the coral cliffs on the northwest side of Tinian, they rammed the walls, fixing the ramps home. The LVTs then reversed, with the flexible ramp boards falling into place along two steel beams forming the main structure of the contraption. Seabee teams ensured the ramps were functional, then the LVT landing force simply crawled up the ramps onto the island, surprising the Japanese defenders yet again.

Difficult terrain, coral reefs, and unpredictable tides and weather caused by typhoons are extremely common throughout the First Island Chain, especially all across the South China Sea, where the PLA has already built multiple military bases. These are basic conditions which the USMC needs to be prepared to operate under, something the PLA has kept in mind by retaining tracks on their ZBD/ZTD Type 05 series vehicles.

The Corps developed this blind spot because safety minders have castrated modern amphibious training. Practice beaches are calm, flat, known entities with generally simple and sloping underwater hydrography; essentially the opposite of what troops will encounter in combat, where the enemy will deny easy beaches and attempt to force attackers to funnel into the most dangerous approaches available. The ACV’s wheels almost certainly cannot negotiate sharp coral reef features well, but time will certainly tell. 

Even the primary advantage of wheels (speed) is negligible in a First Island Chain fight across small islands. Unless the Corps is ordered to invade mainland China or fight across the home islands of Japan, the top speed difference is likely not worth the severe reduction in ability to negotiate underwater obstacles. One of the original precepts guiding the design of the ACV according to a previous program manager was the requirement to keep up with armored follow-on forces attempting to break out of the beachhead. Besides for the obvious fact that the Marine Corps got rid of all its M1 Abrams tanks and that main battle tanks are rarely used in amphibious operations, the top speed of an M1 is about 45 MPH on hardball road. The legacy AAV is also capable of 45MPH on hardball road, which is a head scratcher. Even the Army’s new M10 Booker / Mobile Protected Firepower / light tank/not a tank is only rated at 45 MPH on hardball. The ACV achieves about 60 MPH on roads, which matches the performance of the Army’s Stryker. 

Road from Keelung/Jilong City to Bali Beach, Google Maps

In the example above, movement by road from Keelung/Jilong City (the port on Taiwan’s northeast side) to Bali Beach travels along a roughly 50km route. An ACV traveling 60 MPH with no breaks can make the trip in 31 minutes. An AAV or M1 Abrams can make the trip in 41 minutes. It is true that this is a ~33% increase in speed, but significant time savings are not realized from high road speed unless longer ground movements are required. The increased speed of the ACV will still be valuable in tactical engagements with enemy forces. These arguments are not meant to conclude that the ACV is terrible, simply that different tradeoffs should have been prioritized for such a vehicle.

On a final note, a known problem with the ACV at least as of 2020 was tire degradation during desert maneuvers, causing 2 hour delays for tire replacement during operational testing. According to an official evaluation, only some of the tire issues were attributable to improper adjustment of the central tire inflation system (CTIS), while an unknown portion of the issues were attributed to operating in a desert environment.. Guess what the desert and tropical beaches have in common? Sand and heat, commonplace challenges an amphibious vehicle must answer during combat.

The Marine Corps is not doing itself, amphibious warfare, or the concept of the armored amphibious tractor justice by simply purchasing an Italian steel box to check another box.

Solutions

Embrace Amphibious Operations Holistically: It is important that the services, especially the Marine Corps, do not get sucked into a purely Taiwan oriented way of thinking. Besides which side has an advantage over Taiwan, there is another extremely important question about the larger region: which side has more ability to operate throughout the entire 4,500+ miles of the First Island Chain as a whole, from the Kurils of Russia to the Riau Islands of Indonesia? The entire FIC is solidly archipelagic in nature, with no exceptions. Operating throughout this area requires well equipped naval and marine forces, and it is clear that Beijing understands this.

ACV 1.2: The USMC should invest now and modify the ACV 1.2 standard to require tracks. All ACV vehicles produced from that point on should be tracked models. The ACV-30 test concept needs to conclude successfully and the autocannon turret needs to be included as a baseline weapon for all models. A variant focused on UAV operations/ISR should also be produced.

High Water Speed: The US needs to start a national effort to engineer an amphibious test vehicle capable of very high water speed and extreme operational range. The USMC needs help in achieving this requirement, and a unique public-private partnership should be created to support this endeavor.

Protection: Heavy slabs of composite tank-like armor are almost certainly not going to be the most effective form of protection on the future battlefield. A far more effective long-term approach would be to lighten out the ACV and then devise a super lightweight active protection system utilizing soft and hard kill measures to defeat common battlefield threats. This would help the ACV leapfrog ahead of the ZBD/ZTD and also be installable on the next generation of amphibious vehicles. Another future initiative should focus on creating a manned/unmanned team of manned ACVs linked to unmanned minesweeper vehicles.