general question - what leads to the numbering of units?

[raketenjagdpanzer]

What is the decision process that goes in to that 101st airborne division...well, there weren't 100 airborne divisions that preceded it, were there

394th Tank Guards, 5th armored (actually we did used to have 5 armored...excuse me, ANY armored divisions), 344th TFW -

what's the pattern here Or is there none Does someone just come up with a unit composition and stick a number to it, whatever sounds good that day "Hey, have we used 199th No 199th it is."

[Legbreaker]

Can't speak for the US of course, but in this part of the world they started at 1 and went from there.
During WWII though things changed somewhat. In a show of respect to the original WWI units, a "2" was placed in front so that 14 Battalion was known as 214 Battalion.

It all changed again though a few years post war but essentially it was still #1 to whatever....

[James Langham]

if your own side doesn't understand it what chance has the enemy...

In the UK it is mainly historical tradition.

[Fusilier]

there weren't 100 airborne divisions that preceded it, were there

Not airborne, but the 101st was not originally an airborne unit. Same with the 82nd for example.

[dragoon500ly]

This is a rough breakdown of how US divisions were numbered, at least in WWII.

1-25 were Regular Army divisions
26-59 were National Guard divisions
60-110 were National divisions

The national guard divisions are normally linked with 1-3 specific states and, at least until they hit combat, had a strong contingent for troops from the state. The national divisions were filled with draftees from the very beginning.

In the post war era, the 82nd and 101st were converted into Regular Army in honor of their combat record;wereas the 11th, 13th and 17th Airborne Divisions were deactivated and remained that way except for short periods, i.e. in the Vietnam War, the 1st Airmobile Cavalry Division had been the 11th Airborne Division (Airmobile) during its original training.

As far as the brigade/regimental numbering....there is a rumor that the Pentagon writes 1-1,000 on slips of paper and then draws numbers at the Christmas Party...

[ArmySGT.]

What is the decision process that goes in to that 101st airborne division...well, there weren't 100 airborne divisions that preceded it, were there

394th Tank Guards, 5th armored (actually we did used to have 5 armored...excuse me, ANY armored divisions), 344th TFW -

what's the pattern here Or is there none Does someone just come up with a unit composition and stick a number to it, whatever sounds good that day "Hey, have we used 199th No 199th it is."

The Divisions and Regiments are numbered sequentially from creation. Most Divisions are de-activated, the Colors furled, and the Lineage and Honors recorded. The type of Division has always me adaptable. The 82nd was an Infantry Division before it was Airborne. The Armor and Cavalry are low numbers as they were not often created as whole Divisions centered on that concept. Armor and Cavalry units were mainly created in the Regimental systems and part of an Infantry Divisions organization.

[dragoon500ly]

Well, the US Army solution has always been a bit confusing...

Prior to the Civil War, division's were named after their commander, i.e. Lee's Division in the Revolutionary War/1812 era.

During the Civil War, divisions were numbered within their corps, i.e. 1st/2nd/3rd Divisions, IX Corps, Army of the Potomac.

In the post-ACW era, divisions were organized to control military units in a specific region, i.e 5th Military Division controlled the six regiments assigned to patrol Texas and the Indian Territories. These didn't last out Reconstruction and were replaced by Departments, i.e. Department of Montana.

When the Spanish-American War kicked off, the Civil War style was followed.

Around 1910, the US Army started to number divisions in sequence, but they did not use the Infantry/Cavalry modifiers, so... When WWI kicked off you had the 1st Division, 3rd Division and 82nd Division, American Expeditionary Force (just to name a few).

This new style was followed until the 1925-28 period, when the Infantry/Cavalry modifier was added, i.e. 1st Cavalry Division, 3rd Infantry Division.

With the possibility of war in Europe, planning for a vastly increased army started in 1935-38. The divisions were broken up into blocks and assigned as follows: 1st-25th was assigned to the Regular Army; 26th-60th belonged to the National Guard and 61st-110th belonged to the National Service.

This is pretty much the system that has remained in place since 1946, with the exception of the 82nd and 101st being assigned to the Regular Army block.

Regiments follow roughly the same system...1-100 are assigned to the Regulars; the National Guard has the 101st-250th and the National Service has the 251st-400th. The Armor regiments use this system as well.

The Airborne is the confusing block with units ranging from the 187th-518th. But they were originally rasied as NG/NS units before being assigned to their divisions, this is why you see the initial organizations of the 11th Abn with the 187/188/511; the 13th Abn with 88/326/515; the 17th Abn with 193/194/513; the 82nd with 325/504/505 and the 101st with 327/401/402
regiments....and just to throw a monkey wrench into the system, the 71st Infantry Division (a NS unit), was made up of the 5/14/66 Infantry Regiments (all RAs).

Finally, there are numerous brigades/regiments that bear 4(5) digit numbers. These tend to be engineer units or combat units organized for specific purposes, but their numbering is usually in sequence.

[Adm.Lee]

As an expansion of the above....

Infantry regiments were originally assigned during WWI, when the National Guard received those 26-50 numbers. Each division had 2 brigades, each of 2 regiments, and these were numbered to match. So, my home state of Ohio's 13 infantry regiments and 1 battalion (colored) were shuffled about to become the 37th Division, with the 73rd and 74th Brigades, 145th-148th Infantry Regiments. Also, the 112th MP Company, 112th Medical Detachment, 112th this, 112th that, and so on. The Field Artillery Brigade was the 62nd, and its three regiments were the 134th-136th. These got scrambled a bit during the early stages of WW2 (I have a big list of Ohio's NG units) and more so since then.

Note that if you multiply the division number by 2, you can derive the infantry brigade numbers, and if you multiply it by 4, you can tell the regiment's numbers. This worked for British brigades (certainly not battalions) in both World Wars, too-- 3 brigades per division-- the 51st has the 151, 152, 153 brigades, and so on.

This worked for the NG and AUS (draftee) divisions, but not the Regulars, since those were assembled by putting together what regiments they could find. I'm pretty sure I read that the 1st Division formed around New York City, and the 16th, 18th, 26th and 28th regiments were based or organized from there.

When the regiments were broken up after Korea, they started assigning regimental numbers to battalions that had some affiliation with their parent division. This eventually went giggle-piggledy, and you've got what you see today (if you can bear to look at it).

When Gens. Marshall and McNair started raising the many new units and formations they would need for WW2, they used numbers to help ID some combat units types.
100s- lots of field artillery brigades, but I'm not sure if that's on purpose.
500s- parachute infantry regiments or battalions, but the glider regiments kept the numbers of their parent divisions. Thus the 325th (close to 4x82) stayed in the 82nd Airborne Division.
600s- some antitank/tank destroyer battalions
700s- tank battalions not in armored divisions, some tank destroyer battalions (converted from tank units)
800s- tank destroyer battalions
900s- engineer construction regiments
1000s- engineer special or port brigades
1100s- engineer combat brigades
Field artillery had its own numbering, I haven't picked up the pattern, if any. Often, they kept the numbers of the regiments they replaced.

Artillery & engineer battalions, service units, support units: I got nuthin'

[Sanjuro]

In the British Army, the numbering of divions went no lower than brigade level; assigned regiments were known by their names (in the 20th Century anyway). As has already been posted in another topic, each regiment usually had two battalions, but only the first battalion would be assigned to duty- the second would be a replacement, garrison or reserve formation.
Of course, in wartime extra battalions were formed in many regiments- sometimes as many as 15. These extra battalions would not be assigned to the same division as their "parent" battalion.
Of course, even in the 20th Century, there were were plenty of battalion and regimental commanders who would use the older (Napoleonic War or earlier) numbered designation for their units as a way of highlighting the link with past campaigns (the 42nd Foot as a name for the Black Watch, for example).

[pmulcahy11b]

My personal belief about the numbering of units is that it has something to do with Generals, lots of beer, and a long weekend...

[pmulcahy11b]

500s- parachute infantry regiments or battalions, but the glider regiments kept the numbers of their parent divisions. Thus the 325th (close to 4x82) stayed in the 82nd Airborne Division.

When gliders got the shaft after World War 2, the 325th was retrained as a parachute unit. Thus the 325th is the only one of the 82nd's four infantry brigades to be designated AIR (Airborne Infantry Regiment) instead of PIR (Parachute Infantry Regiment), as the use of the term "Airborne" did not come into widespread use until near the end of World War 2.

[Adm.Lee]

In the British Army, the numbering of divions went no lower than brigade level; assigned regiments were known by their names (in the 20th Century anyway). As has already been posted in another topic, each regiment usually had two battalions, but only the first battalion would be assigned to duty- the second would be a replacement, garrison or reserve formation.
Of course, in wartime extra battalions were formed in many regiments- sometimes as many as 15. These extra battalions would not be assigned to the same division as their "parent" battalion.
Of course, even in the 20th Century, there were were plenty of battalion and regimental commanders who would use the older (Napoleonic War or earlier) numbered designation for their units as a way of highlighting the link with past campaigns (the 42nd Foot as a name for the Black Watch, for example).

I looked this up, the numbers went away in 1881 or so, replaced with the names that the regiments had been using. At that time, there were usually 2 battalions-- one overseas, one at home, and 1-2 more in the Territorials. When wartime battalions were raised, those sometimes were brigaded together.