United States Marine Corps
The Marine Corps is a military service within the Navy Department of the United States Department of Defense. Traditionally, they have been an elite force that has been among the first to service in foreign wars. The first well known Marine engagement was in the war with Tripoli over raids conducted by Tripoli based pirates against U.S. merchant ships in the Mediterranean Sea because they failed to pay tributes from 1801 to 1805. (The Treaty of Tripoli is one of the earliest documents that establishes the United States' status of a secular, rather than Christian nation.) A July 20, 2005 article found here notes that prior to World War II, the Marines were a much smaller force and had less independence from the remainder of the Navy (indeed, the Navy is now organizing its own security forces to replace some roles the notion of a Marine was invented to fill).
The Marines specialize in amphibious assaults, are the primary source of U.S. embassy guards, and have their own helicopters and fixed wing aircraft. Out of respect for their elite status, the Marines were largely spared the deep cuts in force numbers experienced by the Air Force, Army and the remainder of the Navy with the end of the Cold War. The Marines have the lowest ratio of officers to enlisted men (11%), the smallest percentage of women (6%), and the youngest and least experienced soldiers of any of the services in the armed forces. While the Army has historically made significant distinctions between the 15% of its soldiers who have primarily combat roles and the 85% who have primarily non-combat roles, the Marines have traditionally emphasized the idea that each Marine is a rifleman first, and any other type of specialist second.
There are currently about 176,000 Marines in active duty service. There is no Marine national guard. There is one Marine Reserve division and one Marine Reserve Air Wing.
Marine forces are organized in a manner similar to, but with material differences from the Army.
Most Marines serve in one of three Marine Expeditionary Forces, with about 47,500 Marines each, consisting of a Marine division, 330 aircraft (a Marine Air Wing) and a force service support group. One is based at camp Pendleton in California, one at Camp Lejeune in North Carolina and one at Camp Butler in Okinawa, Japan. Some Marines, however, serve in seperate units, for example, as embassy guards or on Naval ship or to smaller mixed units such as a Marine Expeditionary Unit of about 2,700 Marines with air and support units as well.
An Army squad typically has about nine or ten soldiers in it. A Marine squad typically has about twelve marines. Marine organization then relentlessly follows a rule of three, with three squads in a platoon, three platoons to a company, three companies to a battalion, three battalions to a regiment, three regiments to a brigade, and three brigades to a division.
Thus, a notional Marine division has three brigades, nine regiments, twenty seven battalions, 81 companies, 243 platoons and 729 squads of twelve Marines in three fire teams each. This is complicated by headquarters units and the like, however. Still Marine divisions are smaller than Army divisions which have about as many personnel as an entire Marine Expeditionary Force.
The Marines use Navy F-18 and Harrier AV-8B fighter jets (which are notable for their ability to hover), as well as helicopters, transport planes and tanker planes. Current plans call for the Harrier AV-8B jets to be replaced the F-35B which will have similar capabilities (this source says that the Marines plan to buy 480 F-35Bs, with additional purchases of this variant made by the United Kingdom Royal Navy and the Air Force). The top aircraft procurement priority for the Marines is the V-22 Osprey, a propeller based transport fixed wing plane that has about the same capacity to carry troops and cargo as a medium sized transport helicopter, and can convert to helicopter mode. This would allow the V-22 to travel for much longer distances than helicopters with comparable carrying capacity. But, this program has been repeatedly delayed by technical difficulties.
In anticipation of the V-22, the Marines have also begun a program to design a ground vehicle that the V-22 and its CH-47 helicopters can carry. These aircraft are too small to carry a Humvee (the standard military utility vehicle) or heavier armored vehicles. Currently, tests have been conducted using World War II era jeeps and small commercial pickup trucks. The proposed vehicle, currently called the ITV, would be unarmored but able to carry 3-4 Marines and their supplies and heavy weapons a substantial distance (comparable to a civilian motor vehicle) over fairly rough terrain for a wheeled vehicles. Some prototypes resemble big dune buggies. About 2000-4000 ITVs are expected to be purchased.
The Marines use a variety of ground combat vehicles and weapons most of which are also used by the Army. The most distinctively Marine ground combat vehicle is the LAV, an amphibious armored personnel carrier roughly in the same class of vehicle as the Army's Stryker vehicle. A replacement, which would be much faster in its aquatic mode, sometimes called the AAAV (Advanced Amphibious Assault Vehicle) or MEV (Marine Expeditionary Vehicle) has been delayed but not cancelled in the current Defense Department budget.
The V-22 and MEV are both part of a doctrine that calls for Marines to deploy in amphibious assaults from ships located "over the horizon" (i.e. 30-40 miles at sea), where the ships deploying them are less vulnerable to threats particular to coastal waters.