Because of its proximity to Laos and the Ho Chi Minh Trail, the A Shau Valley in the mountains of southern Vietnam was one of the most hotly-contested regions of the country during the war. The area was sprayed numerous times with Agent Orange, and the site of a nearby former Special Forces camp is still heavily contaminated with dioxin because of the defoliants that were stored there nearly 50 years ago. April 25, 2013.