| Forward Operating Base 4 | |
| Type: | Army |
| Built: | 1967 |
| Pushpin Map: | Vietnam |
| Used: | 1967-72 |
| Condition: | abandoned |
| Occupants: | Military Assistance Command, Vietnam – Studies and Observations Group |
| Battles: | Vietnam War |
Forward Operating Base 4 (also known as FOB 4) is a former Military Assistance Command, Vietnam – Studies and Observations Group (MACV-SOG) Command and Control North base. It was near the Marble Mountains southeast of Da Nang, Vietnam. Seabees from NMCB 12 built sea huts on the base in 1968.[1]
The base was located immediately north of the Marble Mountains and south of Marble Mountain Air Facility.[2]
On the night of 22–23 August 1968, as part of their Phase III Offensive, a company from the Viet Cong (VC) R20 Battalion and a sapper platoon infiltrated the base, killing 17 Special Forces soldiers (their largest one-day loss of the war) and wounding another 125 allied soldiers. Thirty-two VC were killed.[3]
The base is abandoned and the area now consists of sand dunes with some commercial and residential development.