Military Unit Heirarchy

Howdy all,

It’s late, I can’t sleep, and I have a nagging question - so I turn to you all!

In your typical army, how do units fit together? How big are they? Who commands them? I’m currently reading some civil war stuff, and read Band of Brothers a while back.

I get that:
army > corps > division
squad < platoon < company

but don’t really have much understanding other than squads are about 10 people-ish. Can somebody try and break it down for me?

In most militaries the rule of 3 applies. That means three sections make a platoon and three platoons make a company, etc.*

A section in the Greek army consists of 24 men that can be broken down into three squads of 8 men. A squad can be broken into three fireteams which is the smallest subdivision.

In practice there may not be enough people to have all these subdivisions. When I was serving in the artillery, we were just about 30 people in my platoon so we weren’t subdivided in sections or squads.

  • I am not very familiar with the English names of divisions so I may have screwed up

Squad - 9 to 10 soldiers. Typically commanded by a sergeant or staff sergeant, a squad or section is the smallest element in the Army structure, and its size is dependent on its function.

Platoon - 16 to 44 soldiers. A platoon is led by a lieutenant with an NCO as second in command, and consists of two to four squads or sections.

Company - 62 to 190 soldiers. Three to five platoons form a company, which is commanded by a captain with a first sergeant as the commander’s principle NCO assistant. An artillery unit of equivalent size is called a battery, and a comparable armored or air cavalry unit is called a troop.

Battalion - 300 to 1,000 soldiers. Four to six companies make up a battalion, which is normally commanded by a lieutenant colonel with a command sergeant major as principle NCO assistant. A battalion is capable of independent operations of limited duration and scope. An armored or air cavalry unit of equivalent size is called a squadron.

Brigade - 3,000 to 5,000 solders. A brigade headquarters commands the tactical operation of two to five organic or attached combat battalions. Normally commanded by a colonel with a command sergeant major as senior NCO, brigades are employed on independent or semi-independent operations. Armored cavalry, ranger and special forces units this size are categorized as regiments or groups.

Division - 10,000 to 15,000 soldiers. Usually consisting of three brigade-sized elements and commanded by a major general, divisions are numbered and assigned missions based on their structures. The division performs major tactical operations for the corps and can conduct sustained battles and engagements.

Corps - 20,000 to 45,000 soldiers. Two to five divisions constitute a corps, which is typically commanded by a lieutenant general. As the deployable level of command required to synchronize and sustain combat operations, the corps provides the framework for multi-national operations.

Army - 50,000 + soliders. Typically commanded by a lieutenant general or higher, an army combines two or more corps. A theater army is the ranking Army component in a unified command, and it has operational and support responsibilities that are assigned by the theater commander in chief. The commander in chief and theater army commander may order formation of a field army to direct operations of assigned corps and divisions. An army group plans and directs campaigns in a theater, and is composed of two or more field armies under a designated commander. Army groups have not been employed by the Army since World War II.

Above Information Derived from DA Pamphlet 10-1

Other divisions or names might include section, regiments, CAV units, etc…

Here’s how it works in the Israeli military, or at least its infantry. All of these are “textbook” formations - units are rarely at full strength in the field.

Squad - around 10 soldiers. Squads are ad-hoc, not fixed formations, usually commanded by an NCO.

Platoon - 3 squads - 30 soldiers. Platoons can also be ad-hoc. Commanded by a Lieutenant.

Company - 3 platoons + command element (CO, XO, company medic, clerk) - 100 soldiers. Commanded by a Captain.

Battalion - 4 regular companies + 1 HQ company (clerks, operations, infirmary, drivers, cooks etc.). Around 500 soldiers, commanded by a Lt. Colonel.

Brigade - 3 regular battalions + 1 “recon” battalion (special combat troops) + 1 battalion-sized HQ element. Around 2500 soldiers, commanded by a Colonel.

Division - here’s where things get complicated. A division consists of three brigades, either one armored and two infantry or two armored and one infantry; added to that are an artillery battery, a combat engineering battalion, an anti-aircraft element, etc. I have no idea how many soldiers are in one, but I’d guess around 10,000. Commanded by a Brigadier General.

Corps - I think 2 divisions + change.

In the American Army it is hard to say something like “A company has x personnel.” Different types of units have different requirements (of course there is an acronym, MTOE Modified Table of Organization and Equipment). I used to be in aviation. I was in a few line units in Attack Helicopter Battalions (first Cobras, then Apaches). We had about 35 people in the company when it was full. The battalion had less than 300. Then I became a tanker. There were 62 authorized in a tank company. Infantry has a lot more.

Then there is the fact that the Army constantly fiddles with it. The Brigade Combat Team concept that we work with now has changed the makeup of a lot of units. Assets that used to be at the division level are now at the brigade or battalion level.

Brigadier Generals command brigades, which is why they’re called “Brigadier Generals.” Divisions are, in most armies, usually commanded by major generals.

Colonel usually command regiments, in those organizations that have them.

The breakdown given so far is pretty accurate, though of course, it varies.

When I was in Germany, my battalion started pretty normally…5 full companies and 2 smaller detachments (about 40 personnel each). One of the companies I was a platoon leader in had about 200 personnel (pretty big). 6 months after I left, the battalion was huge…11 companies.

When I was a company commander in the National Guard, I had 110 Soldiers, which is a pretty average company size. My battalion only had 3 companies, though, and we were the support battalion for the 2nd Brigade Combat Team, which is quite large.

Not any more…While I’m sure some BGs still command some larger brigades, the vast majority of brigades are commanded by full colonels (O-6). Every brigade I was ever in (and those around us) were commanded by colonels. Divisions are usually commanded by MGs though. (though I’ve definitely seen my share of 1 star commanders in that position.)

‘Brigadier General’ is the accepted English-language translation of the IDF rank of *Tat-Aluf *, the seventh officer rank (or O7, as Americans would have it). Brigades are commanded by an Aluf Mishneh, commonly translated as “Colonel.” The IDF does not have any formation between battalion and brigade.

I’m pretty sure that in the British Army Brigadiers still command Brigades. They are also considered the highest field rank, rather than the lowest flag rank.

Given that he was reading about the US Civil War and Band of Brothers, which is about US Soldiers in WWII, I was referring to U.S. Army hierarchy.

Of course, when we look at the U.S. Civil War, we have to make room for regiments, again. We also have to recall that the Union had a narrower vertical pyramid structure (allowing room for more levels of authority–not necessarily a good thing), while the Confederates had “broader” pyramid structures. (This also meant that a Confederate unit might be larger than a Union unit bearing the same title.)

Here is one overview of Civil War organization terminology.

That’s why that even though the South brought 3 corps to Gettysburg to the North’s 7, both sides had roughly the same amount of troops. For a long time, the Union had too many chiefs, not enough Indians.

They have been tinkering with it since World War II.

Before then, the usual hierarchy was:

Group of Armies—Field Marshal (in the US, “General of the Army”)
Division—Lieutenant General
Corps—Major General*
Brigade—Brigadier (in the US, “Brigadier General”)

The usual grouping in infantry, per my father’s ROTC textbook, was
Squad = 7 privates + a corporal = 8 men
Section = 3 squads + a sergent = 25 men
Platoon = 2 platoons + a lieutenant = 51 men, plus another sergeant or two
Larger units usually consisted of 2 to 4 smaller combat units, plus a staff unit.

*Up until about WW1, the Marine Corps was just that: a corps.
The Commandant of the Corps was a major general.

You’re all leaving out the smallest unit, which is the “fire team”. There are (or were) three fire teams to a squad, a fire team consisting of four men, generally a fire team leader, automatic rifleman and two riflemen. A squad consisted of up to fourteen men: three fireteams, a grendadier and a squad leader. I realize that with the changes in weaponry, the composition has likely changed over the years.

Dad was in ROTC before WW2. In his textbook, a squad was 5 men with Springfields, 2 men operating the B.A.R., and the corporal supervising. :slight_smile:

Slight tangent: where do dedicated support units start to come in? How big does the unit have to be to include cooks, mechanics in a motor pool, etc?

A Seabee battalion used to be 762 men (optimally staffed). Battalions were completely self-sufficient, with admin staff, mechanics, drivers, cooks, you name it.

Fair enough. But we got Brigadier General from the British Brigadier. Originally the rank was made for those who command a brigade. It doesn’t work that way anymore except in those countries that follow the British system.

More than just tinker. In 1957 they did away with regiments as they were used before. Then they went to the Combat Arms Regimental System. They did away with that in 1981. By the time I came enlisted in 1989 regiments were in name only. You were part of a regiment just for the lineage. As a command and control entity it did not exist. Except for a few separate units such as Armored Cavalry Regiments. They are bigger than brigades but smaller than divisions and are expected to operate independently. ACRs are usually Corps assets and not attached to a division. In the last few years there has been another major change. The army is being divided into Brigade Combat Teams. The theory is to incorporate division assets such as support and artillery into the brigades. They want brigades to be self sustaining and able to be deployed independently if needed. As it is currently being used a division command structure is deployed and will command several BCTs in the field. These BCTs do not have to come from that division.

Cooks and mechanics are assigned at the company level. Mechanics at that level only have the equipment to fix a certain level of equipment. If more is needed it gets pushed up to a higher level of maintenance. In practice cooks and mechanics are often consolidated at the battalion level when deployed.

Nitpick again.
A “military unit” is the smallest entity capable of indpendant operations. Below that wou;d be sub-units. Above that would be military formations.
In most commonwealth derieved militaries a unit is a battalion, while brigades, divisions and corps are formations.

It should be remembered that operational requirements may cause certain military entities to be reinforced or denuded as necessary. For example in the Northern France Campiagn in WWII, the US Third Army had two corps, while the Third Army had 4.
Friend of mine in the Pakistan Army as a company commander, at one point when occupying a series of strategic heights in Kashmir that were under severe pressure was given two additional rifle platoons and an additional weapons platoon, meaing he commanded closer to 450 mean than the 250 he normally would have.