Question 3: What is Operation Ranch Hand?
The U.S. military’s herbicide program in South Vietnam began in August 1961 and ended in October 1971, under the overall codename “Operation Trail Dust.”
Within this program were several operations and plans with different codenames. Among them, the core mission was “Operation Ranch Hand,” which involved spraying herbicides from the air using C-123 transport aircraft.
Source: From the book 120 Questions and Answers about Agent Orange/Dioxin