The 120th Tactical Fighter Squadron, Colorado Air National Guard, arrived at Phan Rang Air Base, South Vietnam, during the concluding days of the second Viet Cong offensive of 1968. The squadron was ordered into active federal service as a result of the Pueblo incident in January 1968, along with three other F-100 tactical fighter squadrons: 136th Tactical Fighter Squadron, New York, 174th Tactical Fighter Squadron, Iowa, 188th Tactical Fighter Squadron, New Mexico. The 120th Tactical Fighter Squadron entered combat on 5 May 1968, two days after its arrival, and completed its 1,000th mission 51 days later.

During the Air National Guard's eleven months of service in Vietnam, the four F-100 squadrons flew 24,124 combat sorties and accumulated 38,614 combat flying hours. The Air Guard's record proved, once again, the combat-ready status and professionalism of the Air National Guard.