This is the Vietnam patch for the 101st Airborn Medivac. 4" in diameter.
Medical evacuation helicopters were the lifeline of the Vietnam War. Affectionately known as medevacs or dustoffs a nickname originally taken from the radio call sign of Army chopper pilot Major Charles L. Kelly, who was killed in action on July 1, 1964 these Bell UH-1 Huey airborne ambulances and their brave crews saved the lives of thousands of wounded soldiers.
The 101st Airborne Divisions 326th Medical Battalion formed an air ambulance platoon known as Eagle Dustoff that was responsible for aerial medical evacuation of casualties in its area of operations, including some of the most infamous hot spots in all of Southeast Asia. In the spring of 1969 that area included the rugged A Shau Valley, on the western edge of Thua Thien province near Laos, which remained a Communist stronghold throughout the war. Eagle Dustoff crews also evacuated casualties from the mountain known as Hamburger Hill, where elements of the U.S. Armys 101st Airborne and two battalions of the 29th NVA Regiment engaged in a bloody 10-day slugfest in May 1969 that resulted in 446 American casualties. In early 1972 the 326ths medevacs provided support for South Vietnamese forces engaged in Operation Lam Son 719, during which ARVN troops invaded Laos to disrupt NVA supply lines and destroy base camps.