ERDL pattern is a camouflage pattern developed by the United States Army at its Engineer Research & Development Laboratories (ERDL) in 1948. It was not issued to elite reconnaissance and special operations units until early 1967,during the Vietnam War.
The pattern was initially produced in a lime-dominant colorway, consisting of large organic shapes in mid green and brown, black ‘branches’, and light green ‘leaf highlights’. Shortly thereafter a brown-dominant scheme (with the light green replaced by light tan) was manufactured. The two patterns are also known as "Lowland" and "Highland" ERDL, respectively.
The United States Marine Corps (USMC) adopted the brown ‘Highland’ version as standard issue from 1968, and later the U.S. Army introduced it on a wide scale in Southeast Asia. A third variation, known as 'Delta' from an alleged use in the Mekong Delta area of South Vietnam, was issued in the early 1970s. By the end of the Vietnam War, American troops wore camouflage combat dress as the norm.'Delta' ERDL is the same as 'Highland' pattern, but the black 'branches' appear thicker and less detailed. The ERDL-pattern combat uniform was identical in cut to the Olive Drab (OD) jungle fatigues it was issued alongside. Following the withdrawal of the U.S. military from Vietnam in 1973, the Army no longer routinely issued camouflage clothing. The 1st Battalion, 13th Infantry Regiment wore the ERDL-leaf pattern as an experiment in the early 1970s in Baumholder, Germany. The USMC continued wearing the transitional ‘Delta’ ERDL pattern, which became general issue in the mid 1970s. It was to be used to equip the Rapid Deployment Force (RDF) while on tropical missions. Photographs during the 1979 Iranian hostage crisis showed U.S. Embassy Marines wearing the RDF version ERDL uniforms when they were taken prisoner by Iranian revolutionaries. It was not until 1981 that the Army approved another camouflaged uniform. That year it officially introduced the battle dress uniform (BDU) in M81 Woodland pattern , an enlarged and slightly altered version of ERDL-leaf, to supply all arms of the US Forces. The last batches of the ERDL fatigues saw service during Operation Eagle Claw, Beirut and the Grenada Invasion.