Eli5. Why do military groups (101st airborne for example) seem to be numbered in random order
In: 1833
Because units are activated and deactivated. Like in ww2 with a massive amount of men they needed new units. After the war only the hardcore units that had a lot of combat achievements stayed and the rest were deactivated when the military down sized.
In WW1, the War Department set aside division numbers based on their origin. Active Army divisions were to be numbered 1-25, National Guard divisions 26-75, and Reserve divisions 76 and up.
In the end, only active divisions 1-20, Guard divisions 26-42, and Reserve divisions 76-102 were ever organized, 64 infantry divisions in total, plus one Cavalry division. And the 102nd was never fully organized.
In WW2, they began activating divisions along the same numbering system. They decided to limit the divisions to 100, but didn’t quite make that, as they decided to stop organizing new divisions in favor of providing replacements for existing divisions.
The War Department decided to take 82nd and 101st and convert them to Airborne divisions and at the same time bring them into the Active Army.
Units are generally deactivated and reactivated based on a points system based on the number of campaigns they have participated in and the type of division. So 101st remains in existence despite the high number.
Because units are activated and deactivated. Like in ww2 with a massive amount of men they needed new units. After the war only the hardcore units that had a lot of combat achievements stayed and the rest were deactivated when the military down sized.
Sometimes it’s a trick
Like forming SEAL Team 6, when only two other teams existed, suggesting that they had 3 more ‘secret’ Teams already.
Plus it makes signalling or talking on radios much easier when the unit names are clear, the number 5 isn’t used much as it can sound too much like ‘fire’, 1 0 1 comes across really clearly in contrast.
The 82nd Airborne is another unit that survived downsizing the Army after WWII.
Also, in peacetime there are no one-star admirals and generals, along with five stars too.
When there is a huge mobilization, more units are temporarily created to keep each unit a manageable size
Unit numbers are generally sequential. Often, they reserve certain ranges of numbers for a certain role (such as for reservists or for for a different type of unit or something). If an army shrinks and has to cut those units, it’s probably going to try to keep the more prestigious ones.
Let’s take your example of the 101st Airborne Division.
In the numbering convention of the United States Army, division numbers 1-25 were active duty, 26-75 were National Guard, and anything above that was Army Reserve. Unlike some other armies, the United States doesn’t number armor divisions or cavalry divisions in the same sequence, so right now if the United States Army brought its heavy armor to bear all on one front, you would see 1st Infantry Division, 1st Cavalry Division, and 1st Armored Division rolling in with their tanks and other heavy tracked vehicles, though currently there are no other divisions in either the armor sequence or the cavalry sequence.
The Army Reserve doesn’t have combat arms troops anymore, but a few of those numbers are in use for other purposes such as 100th Infantry running certain training units. National Guard still has a few divisions such as 29 and 42. The last armor division other than 1st Armored was 49th Armored in the Texas Army National Guard.
82nd Airborne and 101st Airborne were originally Army Reserve infantry divisions created during the World War I expansion of the Army. 82 saw combat (the most decorated American of the war, Alvin York, was. In this division), but the war ended before 101 made it to Europe and it was a reserve unit until those two divisions were organized as parachute divisions. After the war when the Army was downsizing and returning the higher-numbered divisions to reserve status, they kept 82 and 101 as active-duty divisions because the name is famous and draws lineage to people who the Army likes to talk about and the 101st keeps the airborne name even though they don’t jump out of planes anymore (although when 101 was reconstituted during Vietnam as an air assault division riding helicopters into battle, it was originally as the 11th Airborne Division).
Since 1945, the United States Army has never been as large as it was during the war and some of the divisions during the war had been fake divisions to fool German spies even if they existed in the World War I Army, there are a lot of gaps in the number sequence.
Sometimes, the Army brings back divisions. Most recently, the 25th Infantry Division’s two brigades in Alaska were reorganized as the 11th Airborne Division (the only WWII Pacific parachute division) so 25ID is now just the guys in Hawaii. Around 10-15 years ago, they did the same thing and revived 7th Infantry Division out of the 2nd Infantry Division brigades in the Continental United States, so 2ID is now only the units in Korea.
Sometimes it’s a trick
Like forming SEAL Team 6, when only two other teams existed, suggesting that they had 3 more ‘secret’ Teams already.
Plus it makes signalling or talking on radios much easier when the unit names are clear, the number 5 isn’t used much as it can sound too much like ‘fire’, 1 0 1 comes across really clearly in contrast.
Sometimes it’s a trick
Like forming SEAL Team 6, when only two other teams existed, suggesting that they had 3 more ‘secret’ Teams already.
Plus it makes signalling or talking on radios much easier when the unit names are clear, the number 5 isn’t used much as it can sound too much like ‘fire’, 1 0 1 comes across really clearly in contrast.
Unit numbers are generally sequential. Often, they reserve certain ranges of numbers for a certain role (such as for reservists or for for a different type of unit or something). If an army shrinks and has to cut those units, it’s probably going to try to keep the more prestigious ones.
Let’s take your example of the 101st Airborne Division.
In the numbering convention of the United States Army, division numbers 1-25 were active duty, 26-75 were National Guard, and anything above that was Army Reserve. Unlike some other armies, the United States doesn’t number armor divisions or cavalry divisions in the same sequence, so right now if the United States Army brought its heavy armor to bear all on one front, you would see 1st Infantry Division, 1st Cavalry Division, and 1st Armored Division rolling in with their tanks and other heavy tracked vehicles, though currently there are no other divisions in either the armor sequence or the cavalry sequence.
The Army Reserve doesn’t have combat arms troops anymore, but a few of those numbers are in use for other purposes such as 100th Infantry running certain training units. National Guard still has a few divisions such as 29 and 42. The last armor division other than 1st Armored was 49th Armored in the Texas Army National Guard.
82nd Airborne and 101st Airborne were originally Army Reserve infantry divisions created during the World War I expansion of the Army. 82 saw combat (the most decorated American of the war, Alvin York, was. In this division), but the war ended before 101 made it to Europe and it was a reserve unit until those two divisions were organized as parachute divisions. After the war when the Army was downsizing and returning the higher-numbered divisions to reserve status, they kept 82 and 101 as active-duty divisions because the name is famous and draws lineage to people who the Army likes to talk about and the 101st keeps the airborne name even though they don’t jump out of planes anymore (although when 101 was reconstituted during Vietnam as an air assault division riding helicopters into battle, it was originally as the 11th Airborne Division).
Since 1945, the United States Army has never been as large as it was during the war and some of the divisions during the war had been fake divisions to fool German spies even if they existed in the World War I Army, there are a lot of gaps in the number sequence.
Sometimes, the Army brings back divisions. Most recently, the 25th Infantry Division’s two brigades in Alaska were reorganized as the 11th Airborne Division (the only WWII Pacific parachute division) so 25ID is now just the guys in Hawaii. Around 10-15 years ago, they did the same thing and revived 7th Infantry Division out of the 2nd Infantry Division brigades in the Continental United States, so 2ID is now only the units in Korea.
Unit numbers are generally sequential. Often, they reserve certain ranges of numbers for a certain role (such as for reservists or for for a different type of unit or something). If an army shrinks and has to cut those units, it’s probably going to try to keep the more prestigious ones.
Let’s take your example of the 101st Airborne Division.
In the numbering convention of the United States Army, division numbers 1-25 were active duty, 26-75 were National Guard, and anything above that was Army Reserve. Unlike some other armies, the United States doesn’t number armor divisions or cavalry divisions in the same sequence, so right now if the United States Army brought its heavy armor to bear all on one front, you would see 1st Infantry Division, 1st Cavalry Division, and 1st Armored Division rolling in with their tanks and other heavy tracked vehicles, though currently there are no other divisions in either the armor sequence or the cavalry sequence.
The Army Reserve doesn’t have combat arms troops anymore, but a few of those numbers are in use for other purposes such as 100th Infantry running certain training units. National Guard still has a few divisions such as 29 and 42. The last armor division other than 1st Armored was 49th Armored in the Texas Army National Guard.
82nd Airborne and 101st Airborne were originally Army Reserve infantry divisions created during the World War I expansion of the Army. 82 saw combat (the most decorated American of the war, Alvin York, was. In this division), but the war ended before 101 made it to Europe and it was a reserve unit until those two divisions were organized as parachute divisions. After the war when the Army was downsizing and returning the higher-numbered divisions to reserve status, they kept 82 and 101 as active-duty divisions because the name is famous and draws lineage to people who the Army likes to talk about and the 101st keeps the airborne name even though they don’t jump out of planes anymore (although when 101 was reconstituted during Vietnam as an air assault division riding helicopters into battle, it was originally as the 11th Airborne Division).
Since 1945, the United States Army has never been as large as it was during the war and some of the divisions during the war had been fake divisions to fool German spies even if they existed in the World War I Army, there are a lot of gaps in the number sequence.
Sometimes, the Army brings back divisions. Most recently, the 25th Infantry Division’s two brigades in Alaska were reorganized as the 11th Airborne Division (the only WWII Pacific parachute division) so 25ID is now just the guys in Hawaii. Around 10-15 years ago, they did the same thing and revived 7th Infantry Division out of the 2nd Infantry Division brigades in the Continental United States, so 2ID is now only the units in Korea.
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