I'm often asked what the elements of command are for the U.S. Marine Corps. Much of the below information was provided by apacherat, a member of our message forum, and a former Marine (actually, there is no such thing as a "former" Marine):
The Marine Corps has the "RULE of THREE." I believe it was invented during the Anna Wars by Edison who invented the fire team concept that is used today. In a nutshell, the rule is this: each Marine has three things to worry about. Three men to a fire team commanded by a Corporal (so there are actually a total of four on the team, when you count the team leader). Three fire teams to a rifle squad commanded by a sergeant. Three rifle squads to a platoon commanded by a Lt.. Three rifle platoons to a company commanded by a Capt. Three companies to a battalion commanded by a Lt Col. etc.
Team: Four individual Marines assigned to a specific team (Three team members, plus the team leader).
Squad: Three Teams are assigned to a specific squad.
Platoon: Three squads are usually assigned to a specific platoon.
Company (or Battery): Three platoons are assigned to a Company (sometimes called a battery). The Company/battery is the lowest level of command with a headquarters element (example, a Company Commander, or Company First Sergeant).
Battalion: Three companies/batteries are assigned to form a battery a battalion.
Regiment: Three battalions form a Regiment (Sometimes called a Brigade).
Division: Three Brigades are assigned to make up a Division.
Marine Corps: Three or more divisions make up the Marine Corps.
MEU: In addition to the above, there are also MEUs (Marine Expeditionary Unit). With a strength of about 2,200 personnel, the MEU is normally built around a reinforced battalion, a composite aircraft squadron, and by a MEU Service Support group. Commanded by a colonel, the MEU is employed to fulfill routine forward deployments with fleets in the Mediterranean, the Western Pacific, and periodically, the Atlantic and Indian Oceans. The MEU is deployed on up to four Naval amphibious ships. The ground combat element (GCE) is the battalion landing team (BLT), an infantry battalion reinforced with artillery, amphibious assault vehicles, light armored reconnaissance assets and other units as the mission and circumstances require. The aviation combat element (ACE) is a Marine Medium Helicopter Squadron augmented with four types of helicopters into a composite squadron. These units include CH-53E "Super Stallions," CH-46E "Sea Knights," UH-1N "Hueys," and AH-1W "Super Cobras." Ace assets may also include the fixed-wing aircraft such as the AV-8B "Harrier" jet. The combat service support element is the MEU Service Support Group (MSSG) formed primarily from force service support groups assets. The MSSG contains all the logistics specialists necessary to keep the GCE, ACE and organic equipment functioning. Included within the MSSG are medical, dental, maintenance, engineering, and other technical experts. The command element (CE) provides command and control of the other three elements. In addition to the MEU commander and his supporting staff, the CE includes specialized detachments providing a direct action capability, naval gunfire liaison capability, reconnaissance, and surveillance and specialized communications and electronics warfare capabilities.
The Marines structure their aviation commands a little differently. The structure for aviation commands are:
Squadron: (applied to flying & non-flying units). In aircraft squadrons, the number of aircraft varies from 4 - 24, depending on the type of squadron. Non-flying squadrons include Marine Aviation Logistics Sqns (supply), Marine Wing Support Sqns (construction), Marine Air Control Sqns (air defense), Marine Air Support Sqns (Airfield control), Marine Tactical Air Command Sqns, Marine Wing Communications Sqns, Marine Wing Headquarters Sqns (Admin).
Group: (3 or more squadrons) Includes Marine Aircraft Group (MAG), Marine Wing Support Group (MWSG), Marine Air Control Group (MACG). The MAGs are usually all helo or all fixed-wing (MAG-36 in Okinawa has a KC-130 sqn attached)
Wing: 3+ Groups. 2 or more MAGs + MWSG, MACG.
For example, 1st MAW has 1 fixed-wing MAG (MAG-12)+ 2 helo MAG (MAG-36 + Aviation Support Element, Kaneohe). 2nd & 3rd MAW each have 2 fixed-wing + 2 helo MAGs. 4th MAW (Reserves) has 4 mixed MAGs
There is no set size (number of troops) assigned to any specific element. The size of an element of command depends primarily upon the type of unit and mission. For example, an aviation squadron would have a different number of troops assigned than an infantry company because it has a different mission, different equipment, and therefore different requirements.