Established on 24 January 1964, the unit conducted strategic reconnaissance missions in the Republic of Vietnam (South Vietnam), the Democratic Republic of Vietnam (North Vietnam), Laos, and Cambodia; carried out the capture of enemy prisoners, rescued downed pilots, and conducted rescue operations to retrieve prisoners of war throughout Southeast Asia; and conducted clandestine agent team activities and psychological operations.
The unit participated in most of the significant campaigns of the Vietnam War, including the Gulf of Tonkin incident which precipitated increased American involvement, Operation Steel Tiger, Operation Tiger Hound, the Tet Offensive, Operation Commando Hunt, the Cambodian Campaign, Operation Lam Son 719, and the Easter Offensive. The unit was formally disbanded and replaced by the Strategic Technical Directorate Assistance Team 158 on 1 May 1972.
A Forward Operating Base (FOB) is any secured forward military position, commonly a military base, that is used to support tactical operations. They may or may not contain an airfield, hospital, or other facilities, and are generally separate from a main operating base by being temporary stations rather than permanent.
On August 23, 1968, an NVA/VC sapper attack was launched on a SOG compound in Da Nang, FOB (forward operating base) 4. Seventeen Green Berets were killed during that attack—the single largest toll of Green Berets killed in Special Forces history.
The above information provided in part by Wikipedia, The Institute of Heraldry, Global Security, and the official websites of the corresponding units and formations.