MILITARY UNIT SIZES

Steve Cole writes:

The military use a bewildering array of unit sizes and types. Here is a short description of the most common, with notes on how these came to be. The list is arranged from the smallest to the largest.
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Team: Four soldiers, led by an E5 three-stripe sergeant. (Note, a Navy "Seal Team" is a wholly different thing, much larger, with some officers in it.)
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Squad: In the US Army, this has two teams, with a total of nine soldiers, one of whom is an E6 (four-stripe sergeant). Marine Corps squads have thee teams and 13-14 guys.
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Section: This is kind of a funky unit, bigger than a squad but smaller than a platoon. In World War I, most armies had sections instead of squads. In current US military usage, a section consists of two squads, and is used only in some special cases. Some platoons have two sections, which may or may not have squads. Most platoons do not have sections at all.
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Platoon: This consists of three squads, led by a first lieutenant (O2) or second lieutenant (O1) with a senior E7 five-stripe sergeant to help him. Most companies are organized into platoons, but some have sections. The rather bizarre Marine Corps TOW anti-tank missile "platoon" is actually a very large company. A tank platoon has four tanks (five tanks until about 1980).
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Company: This consists of three platoons plus a weapons squad. Led by an O3 captain with an O2 first lieutenant and an E8 six-stripe first sergeant to help him. An artillery company is known as a battery. A mechanized cavalry company is known as a troop. (British and most European armies call a tank platoon a troop and a tank company a squadron.) A company is based on the old Roman "century" of 100 soldiers, and can include 100-150 soldiers depending on type. A tank company has fourteen tanks. An artillery battery has six cannons. In the British Army, companies are commanded by majors. In the US Army, this is the smallest unit with a "commander" (platoons have "leaders") but the Marines often call platoon leaders by the title "platoon commanders".
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Team: In US Army usage, this is a company that traded one of its platoons to another company for a platoon of a different type, such as a mechanized infantry company trading one of its platoons to a tank company for a tank platoon.
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Battalion: In current US usage, this unit of about 700-1000 soldiers includes three line companies, plus a mortar platoon, scout platoon, anti-tank company (not in Bradley units which have tank killing built into the vehicles), supply platoon, and other small units. This unit is led by an O5 lieutenant colonel, with two majors and a sergeant-major to help him. This is called a "squadron" in armored cavalry units. This would be called a "regiment" in most European armies. This is the smallest US unit with a staff (S1 personnel, S2 intel, S3 operations, S4 logistics). Under Ronald Reagan, Army mechanized battalions were incredibly powerful organizations with four line companies AND an anti-tank company, but Clinton cut them to three line companies and no anti-tank company. During the American Civil War, a battalion was any group of companies that was smaller than a full regiment. An Air Force squadron (with 12-24 aircraft) is the same size unit.
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Task Force: This is a US Army battalion that traded one of its companies to another battalion for a different kind of company. For example, a mechanized infantry battalion trades one company to a tank battalion, and both become combined arms task forces.
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Regiment: In US usage, this is a historical organization of three identical battalions, plus assorted other units such as an anti-tank company, cannon company, and so forth; at least, that is what it was during World War II. In the Civil War, a regiment had 1,000 men (and was almost always down to 300-500 men due to casualties). This term is really no longer used by the US Army except that armored cavalry brigades are called regiments because the word regiment is so darn cool. A regiment is led by an O6 full bird colonel with a full staff. All current Army battalions are part of "historical regiments" but the battalions rarely serve in the same place.
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Brigade: In current US Army usage, this is a group of two or more line battalions (infantry or tanks), plus a recon company, an engineer company, an attached artillery battalion, and other small units formed into a support battalion, with a total of maybe 3,000 people. A brigade is commanded by an O6 full bird colonel with a full staff. Until 2001, brigades had three or sometimes four line battalions and about 5,000 people. Now, with more firepower and UAVs and precision smart bombs, two battalions are enough warm bodies exposed to enemy fire. Until 2001, brigades borrowed almost all of their subunits from division. Now, those subunits are more or less permanent parts of the brigade, and the Army rotates brigades through war zones under control of whatever division headquarters is handy. For historical confusion, a Civil War brigade included three to seven "regiments" and was commanded by a brigadier general. An Air Force "wing" is the same size unit.
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Division: This had three line brigades until 2001, and now has four line brigades. In either case, there is also an artillery unit (called "a divisional artillery" but it's a brigade, except that it gives its battalions to the brigades and the artillery commander becomes a member of the division staff and Corps HQ gives the division another whole national guard artillery brigade). There is also an engineer unit (which gives its subunits to the brigades and the engineer commander becomes a divisional staff advisor). Since about 1980, there is an aviation/recon brigade (including the armored cavalry battalion and the helicopters). A division is commanded by a two-star major general with two one-star helpers (one of whom runs operations, the other runs logistics). A division has a military police company to handle traffic and prisoners. Usually, subunits of the MP company work for the brigades. There are some other dibble and dabs of support units in the division, but these days, the division has few troops of its own as the brigades are set up to operate independently.
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Operational Maneuver Group: Used by the Soviets, this was a very big division or very small corps. The Soviets invented this thing just before they went out of business. It was based on the very successful World War II "mechanized corps" organization, which was sort of a really big division. The US Army was officially scared to death of Soviet OMGs.
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Corps: The consists of two or more divisions, led by a three-star lieutenant general. This often has two or three artillery brigades (mostly from the National Guard), plus a helicopter brigade, an armored cavalry regiment, and assorted other support units.
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Army (also known as a Field Army): This includes two or more corps, and in theory is led by a four-star full general (but these days, by a three-star). A field Army always has a mountain of other units like engineers, artillery, aviation, mess kit repair, finance, and so forth. Soviet (and Arab) armies use the term "army" to refer to a group of four divisions, and had no corps.
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Operational Group: This formation was used by the Germans in World War II for tank armies. This was a field army (containing two or three corps and eight or ten divisions) but did not get the title "army" until a year later when they quit calling them Operational Groups. The infantry guys who ran the German Army did not want the younger tank generals to have the glory of being "army" commanders.
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Army Group: This consisted of two or three field armies plus a lot of support units. This has not used since World War II because armies are smaller. The Soviets in World War II and until the collapse in 1990 used the term "Front" to mean what Western units called an Army Group.