Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!lll-winken!uwm.edu!linac!att!cbnews!cbnews!military From: graham@cs.washington.edu (Stephen Graham) Newsgroups: sci.military Subject: A Quick and Dirty Guide to US Unit Numbering Message-ID: <1991Mar7.014546.2986@cbnews.att.com> Date: 7 Mar 91 01:45:46 GMT Sender: military@cbnews.att.com (william.b.thacker) Organization: U of Washington, Computer Science, Seattle Lines: 77 Approved: military@att.att.com From: graham@cs.washington.edu (Stephen Graham) A Quick and Dirty Guide to the Numbering of US Army Units (and really brief comments on the Marines and Air Force) Corps, Armies, and Army Groups These units are raised and numbered in sequence as necessary. The 1st through 5th Armies are administrative units within the Continental US. Corps currently active are derived from WWII units, which were numbered as they were raised. Army Groups are now multi-national units (usually NATO) and are named. Divisions Divisions are numbered in sequence within the general divisions Infantry, Armor, and Cavalry. The numbering sequence derives from WWI and WWII. Regular Army (RA) divisions are numbered 1-25. National Guard divisions fall within 26-50 and Divisions to be raised from draftees are numbered 51 and above. In practice, Training Divisions are numbered 70 and above, since the original pattern had WWI draftee divisions numbered 76 and above. Very few National Guard divisions exist any more. Recently active RA divisions include: 1st Mech, 2d Infantry, 3d Mech, 4th Mech, 5th Mech, 6th Light Infantry, 7th Light Infantry, 8th Mech, 9th Motorised, 10th Mountain, 24th Mech, 25th Light Infantry, 82d Airborne, 101st Air Assault, 1st Armored, 2d Armored, 3d Armored, 1st Cavalry (armored). The 82d and 101st started out as draftee divisions in WWI, and were converted to RA when they became airborne in WWII Brigades. Brigades are stranger. If they are part of a division, they are numbered as the 1st, 2d, 3d or 4th Brigade of the Xth Division. If independent, Regular Army brigades are numbered 196-199 (a relic from Vietnam, hard to say why). National Guard brigades derive their numbers from one of two places: 1) The number of the WWII National Guard division they derive from; or 2) The National Guard brigade in their area from before WWII. (Prior to WWII, US Army Divisions had two brigades of two regiments each, numbered in sequence according to divisional number: 1st Infantry Division had 1st and 2d Infantry Brigades. The Washington National Guard contributed the 81st Infantry Brigade to the 41st Division, it now provides the 81st Infantry Brigade as a separate unit). Regiments Regiments are now administrative and honorary organizations. Prior to the 1960's, they were the primary combat unit. They are numbered in sequence in each branch (Infantry, Armor/Cavalry, Artillery, Engineer). The numbering sequence is thus: 1-100 Regular Army and Reserves, 101-300 National Guard, 301- draftees. Airborne units are numbered 501 and above. A couple of exceptions: the 187th and 325th Infantry are RA Airborne units, but out of the normal sequence. The 442d is a Reserve unit. I can explain this, but it'd take a while. It makes sense if you know unit histories. Armor and Cavalry regiments are numbered in sequence, as Armor was raised from Cavalry. However, it is possible to have an Armor and a Cavalry regiment with the same number, usually in the National Guard. It's just the way things are. Smaller units (Battalions, Companies, whatever). A mess. Theoretically, they follow the same numbering system as regiments, but not really. Number sequences are unique within each branch, so that you can have the 125th MP Company, 125th Intelligence Co, 125th Quartermaster Co., etc. Sometimes it seems numbers are picked completely at random for a unit. Marines. The Marines still have regiments as combat units. They, however, number all regiments in sequence. So, the 1st Marines are infantry, but the 11th Marines are artillery, etc. Their rational is that everyone's a Marine. Air Force. Air Force unit numbering is very odd. It's more or less random as far as I can tell.