Vietnam Photos- / ARC Identifier: 530612 - Vietnam. As the second phase of operation "Thayer," the 1st Air Cavalry Division (airmobile) is having operation"Irving" in the area 25 miles north of Qui Nhon which lies 400 miles north-northeast of Saigon. The 1st Air Cavalry was given the mission of clearing a mountain range where an estimated two battalions of North Vietnam regulars were supposed to be massing an attack on Hammond Airstrip. Troops of "A" Company, checking house during patrol. , 10/06/1966