The herbicide spraying missions began in Vietnam in 1961, and it has recently been revealed that some took place from Thai bases, including Takhli, as early as 1966. This pre-dates the USAF receiving permission to use herbicides for clearing areas on and around Thai bases for area and perimeter defense, which was given in 1969. The missions in 1966 defoliated areas surrounding parts of the Ho Chi Minh Trail in Laos, near the Vietnam border and north of the Vietnamese Demilitarized Zone and had the approval of both the Thai and Laotian governments.