Ok, so let's be honest - we full on stole the CARS concept from the @BritishArmy. They managed the histories and lineages of their storied regiments like bloodlines of winning racehorses. We tossed ours about willy-nilly. CARS was about creating a sense of belonging & identity https://twitter.com/18airbornecorps/status/1285547909942050819

The Hancock Board in the 1870s assigned battle honors to units. In 1922, the Historical Section of the War Plans Division took over responsibility of developing lineage for all units as well as assigning campaign credit. At the same time, regiments rec'd heraldic crests & mottos

The post-WWI Army, then, created the regimental identity. And this was vitally important. For the Regular Army, this could be done with the stroke of a pen. But for the National Guard, it was a different story. WWI had mashed up different preexisting units; lineage was a mess

The Historical Section released the State Study: every state was sent a list of pre-WWI state units with their post-war lineal counterparts. Units were consolidated with each other to ensure that noted histories did not get lost. NG lineage follows people and location.

Many units that were created for WWI and then inactivated, simply lost their lineages completely if the State Study did not show that their unit was continued in any post-war unit.

Following WWII, the War Department released a similar study, showing unit designations as they appeared at the time of the 1941 mobilization, during the war, & upon return to state control in 1945. In 1946, the War Department provided authorization for states to form units again

The War Department also created a data card for EVERY. SINGLE. unit in WWII. Every. Single. One. With dates, MTOE changes, campaigns authorized, and whether it was inactivated, returned to state control, or some other force structure action

These sets of documents help present day Army historians determine a unit's lineage - connecting the past with the present. In 1981, CARS becomes the US Army Regimental System & provides regimental affiliation for non combat arms units: Engineers, MPs, Ordnance, Chemical, etc.

All Soldiers can now trace their service into a line that goes back to the creation of their branch. It's an often messy system, but it works. And as an Army historian, it's terrifically fun to trace unit lineages & try to find more branch lines for more history & campaigns

The complete confusion to force structure brought during the #AtomicAgeArmy forced the Army's Office of the Chief of Military History to standardize their processes even more, resulting in the creation of the @USArmyCMH in 1973

For more on unit numbering, refer to this: https://angrystaffofficer.com/2020/01/12/army-unit-numerical-designations-where-do-they-come-from/amp/