Why the US Used Agent Orange in Vietnam and What Makes It So Deadly

The United States military sprayed nearly 12,000 square miles of Vietnamese jungles with the chemical defoliant over a 10-year period in an effort to clear large areas of jungle that provided Viet Cong guerrillas with cover, shelter and food.

https://www.military.com/history/why-us-used-agent-orange-vietnam-and-what-makes-it-so-deadly.html