The primary function of the USMC is to conduct amphibious assaults. It consists of three active and one reserve divisions and associated air wings. The air wings each include AV-8B VSTOL and F-18 CTOL jets, attack and light, medium and heavy transport helicopters. The Marine divisions consist of straight-legged infantry battalions supported by towed artillery. Their overall force structure also includes 4 LAV battalions and 8 tank companies. Marine infantry are mounted on tracked LVTs for over-the-beach assaults, or can be delivered ashore by helicopters. For amphibious operations, the LVT can carry half a platoon but, once on shore, it generally only carries a squad. It is very lightly armored, has a high profile, has limited ground clearance, and has a very vulnerable flat bottom. It has one small turret, mounting a heavy machine gun or an automatic grenade launcher for suppressive fire.
The USN currently maintains a mix of up to 33 large amphibious ships to transport Marines, vehicles and supplies. If all of these ships were simultaneously available, they could mount one full division, only 25% of the USMC. But one-third of these ships are generally undergoing overhaul. Therefore, available amphibious ships could only simultaneously embark two regiments (brigades). Prior to 9-11, the USMC generally maintained two forward-deployed reinforce battalions mounted on amphibious ships, one on each coast. It, then, regularly conducted small amphibious exercises. Large scale amphibious exercises were rarely conducted. These ships provide berthing for embarked Marines, cargo holds for vehicles and supplies and hangars and flight decks for Marine VSTOL aircraft and helicopters. They also incorporate floodable wells which are used to transport the LCAC air-cushion vehicles that are now used to transfer vehicles and cargo ashore. Because of the large size of LCACs, only two or three of these can be embarked by each current modern amphibious ship. Consequently, movement of vehicles and heavy equipment across the beach depends on a handful of LCACs. The amphibious ships also have limited numbers of helicopter landing spots and limited hangar space. A forward deployed Marine battalion mounted on amphibious ships will, therefore, have the dedicated support of only 6 VSTOL attack aircraft and be dependent on as few as 4 LCACs. A carrier battle group might be available to support a Marine battalion. USN carriers each embark 48 F-18s. These have to provide defensive CAP and also function as airborne tankers. Relatively few will, therefore, be available for the close air support of assaulting Marines. Supporting USN destroyers and cruisers have SQS-53 bow sonar domes which result in very deep navigational draft. They each mount 1 or 2 MK 45 127mm gun mounts. These gun-mounts each fire 70 pound high explosive shells to a maximum range of 24km at a rate of up to 20 rounds per minute. USN frigates mount a single 76mm gun that provides minimal fire power. The new LCS mounts an even smaller 57mm gun.
World War II destroyers mounted 4 to 6 five inch 38 caliber guns. Each of these was capable of firing a 55 pound high explosive shell out to 18km at a maximum rate of 15 to 18 rounds per minute. These World War II destroyers had much shallower drafts than current ships and could, consequently, operate much closer to shore. They could provide 2 to 4 times as much fire power per ship. During World War II, amphibious assaults also had the support of battleships and cruisers firing at virtually point blank range. Each USN destroyer could then generate greater fire power than the organic artillery of an infantry division. One destroyer was usually assigned to support each assaulting battalion. This level of fire power can no longer be provided.
The hard reality is that the USMC does not currently possess a significant forced entry amphibious assault capability. Amphibious training has all but ceased. Naval gunfire support is grossly inadequate and only a fraction of what was previously available. USN carriers have very limited attack capability, and Marine air wings cannot be fully employed without the availability of nearby conventional airfields. Based on the VSTOL aircraft, which can be operated from large amphibious ships, each Marine battalion can be provided with only about 12 sorties per day of dedicated close air support. Assaulting LVTs are very slow and, hence, have to be deposited close to the shore by large, slow, expensive and vulnerable LPDs. The LPDs are extremely vulnerable to ASCMs, mines and shore defense artillery. It is very difficult to ensure the destruction of mobile ASCM launchers and well-hidden dug-in artillery. Once the LPDs come close to shore, the enemy’s fire control problems are vastly simplified and difficult to defeat. The LVTs, themselves, are easy targets for ATGMs or even conventional anti-tank or anti-aircraft guns. With their limited ground clearance and flat bottoms, they have proven to be catastrophically vulnerable to mines. Very few LCACs are available to support each battalion. The LCACs are thin skinned and vulnerable to all enemy weapons. They are currently the only means available to transport Marine tanks and LAVs ashore during an amphibious assault. The USN, which once fielded over 1,000 LSTs and a vast array of small LSMs and LCTs, today, does not have any available for amphibious assault operations! Combat history, going back to Vietnam, has shown time and again that helicopter borne straight-legged infantry cannot be inserted into well defended areas without experiencing unacceptably heavy casualties. Moreover, because of limited hangar volume, and, more significantly, the lack of landing spots, very few assault helicopters can be simultaneously launched. This limits the size of a heli-borne amphibious operation. Because of the limited lift capability of Marine helicopters, this force would incorporate minimal vehicles and heavy support weapons. Simply put, the Marines exist to execute a mission they cannot currently effectively perform.
The US needs an amphibious capability. But does it need to maintain the expensive illusion of a force entrance capability? Do we need 4 Marine divisions? Do we need a third independent tactical air force in addition to the USAF and USN? In my view, we cannot any longer afford to fund expensive illusions of power. The USMC should be significantly downsized and transformed.
The transformed USMC should consist of only 3 active and 1 reserve reinforced brigade groups. Existing Marine air wings should be disbanded and their fixed-wing squadrons absorbed into the USN or USAF or disbanded. Marine helicopters and UAVs should be cut in numbers and reorganized into smaller units which would support USMC maneuver units as appropriate. The numbers of USN amphibious assets should be down-sized to provide a total lift of one brigade on each coast, of which one-third would be held in reserve with a limited crew or de-commissioned under long-term refit. Two Marine battalions would be irregularly forward-deployed, one operating from each coast. The primary function of these battalions would be special operations, counter insurgency and emergency responses.