On 1 January 1969, under the new U.S. Army Combat Arms Regimental System (CARS), U.S. Army Rangers were re-formed in South Vietnam as the 75th Infantry Regiment (Ranger). Fifteen companies of Rangers, two of which (A-75 & B-75) were based in the USA, were raised from units that had been performing missions in Europe since the late 1950s and in Vietnam since 1966 as Long Range Reconnaissance Patrol and Long Range Patrol companies. These new Rangers were given a unit genealogy traced to Merrill's Marauders.
In Vietnam, the Rangers were organized as independent companies: C, D, E, F, G, H, I, K, L, M, N, O and P (With one notable WWII exception, since 1816, U.S. Army regiments have not included a Juliet or "J" company. Each company from the 75th Infantry (Ranger) was assigned to a major US army combat unit:
· C Company-I Field Force RVN (Republic South Vietnam)
· D Company-II Field Force RVN
· E Company-9th Infantry Division RVN
· F Company-25th Infantry Division RVN
· G Company-Americal Division (also known as the 23rd ID) RVN
· H Company-1st Cavalry Division (Airmobile); also known as the 1st Air Cav Division RVN
· I Company-1st Infantry Division RVN
· K Company-4th Infantry Division RVN
· L Company-101st Airborne Division (Airmobile) RVN
· M Company-199th Light Infantry Brigade RVN
· N Company-173rd Airborne Brigade RVN
· O Company-82nd Airborne Division (3rd Brigade) RVN
· P Company-5th Infantry Division (1st Brigade/Mechanized) RVN
Rangers in Vietnam conducted long range reconnaissance into hostile territory. They collected intelligence, planned and directed air strikes, acted as force-multipliers in conventional operations, assessed aerial bombing damage in enemy-controlled areas, executed hunter-killer missions, both day and night, conducted ambushes, and specially-trained and specially-equipped Ranger snipers killed selected enemy personnel.