On 1 March 1966 the 26th Marine Regiment was activated at Camp Pendleton initiating the formation of the 5th Marine Division.[1]: 357 The 26th Marines moved to Okinawa in August.[1]: 306 Until 4 October the battalion formed the battalion landing team (BLT) of the Special Landing Force (SLF).[1]: 350 The battalion conducted Operation Deckhouse IV from 15 to 18 September. On 27 September the battalion was landed at Da Nang.[1]: 346
At the beginning of 1969 the battalion was responsible for security on the northern approaches to Da Nang including the Hải Vân Pass.[4]: 81 On 1 April the battalion joined the SLF Alpha as the BLT.[4]: 303 On 5 May SLF Alpha launched Operation Daring Rebel.[4]: 307 From 26 May to 10 June the battalion participated in Operation Pipestone Canyon.[4]: 176–8 On 27 June SLF Alpha launched Operation Bold Pursuit which continued until 6 July.[4]: 307 From 10 to 20 July SLF Alpha conducted Operation Mighty Play.[4]: 307–8 The battalion rejoined Operation Pipestone Canyon on 20 July.[4]: 176–84 On 8 August the battalion reembarked on ships and on 7 September began Operation Defiant Stand which continued until 18 September.[4]: 308–9 The battalion then ended its BLT duties and moved ashore replacing the 2nd Battalion, 26th Marines which became the BLT.[4]: 310 On 21 September 1969 the 5th Marine Division was deactivated however the 26th Marines were assigned to the 1st Marine Division.[4]: 356
At the beginning of 1970 the 26th Marines were responsible for the defense of the northern and western approaches to Da Nang.[5]: 27–8 The battalion had its command post on Hill 10 southwest of Da Nang with its TAOR directly below Charlie Ridge (15°56′10″N108°05′42″E / 15.936°N 108.095°E / 15.936; 108.095), a hill mass that projected from the Annamite Mountains that was frequently used by the VC for attacks on Da Nang.[5]: 32 As part of Operation Keystone Bluejay the regiment stood down for deactivation in late February to early March with the 1st Marines taking over most of their tactical area of responsibility.[5]: 28 On 6 March the 1st Battalion 1st Marines relieved the battalion.[5]: 36 From 11 to 19 March 1970 the 26th Marine Regiment redeployed from South Vietnam and was inactivated.[5]: 15