Central Office for South Vietnam

Central Office for South Vietnam (abbreviated COSVN /ˈkɑːzvɪn/; Vietnamese: Văn phòng Trung ương Cục miền Nam), officially known as the Central Executive Committee of the People's Revolutionary Party from 1962 until its dissolution in 1976, was the American term for the North Vietnamese political and military headquarters inside South Vietnam during the Vietnam War. It was envisaged as being in overall command of the communist effort in Republic of Vietnam (South Vietnam), encompassing the efforts of both People's Army of Vietnam (PAVN, or NVA to the Americans), and the National Liberation Front of South Vietnam (NLF, or Viet Cong), as well as the People's Revolutionary Party. Some questioned its existence, but in his memoirs, General William Westmoreland, commander of Military Assistance Command, Vietnam (MACV), insisted its existence and importance were not in doubt.

According to PAVN Major General and later dissident Trần Độ, COSVN did exist and was responsible for organising and directing Viet Cong operations. It was however hierarchically overseen by the Central Office (Trung ương Cục) which directed overall strategy from Hanoi. COSVN existed to coordinate Viet Cong military and political efforts, as part of the wider Communist bid to reunify the country under their rule.

MACV had imagined COSVN as a physically large, permanent structure due to the carefully coordinated and planned nature of Viet Cong activity. It became a near obsessive fixture for US military and political leadership, referred to by some as the "Bamboo Pentagon." In fact, what the Americans called COSVN was a dispersed, highly-mobile headquarters network, often working out of thatched huts in the jungle. There was no centralized, static physical structure overseeing Viet Cong operations, as US and ARVN bombing and search and destroy missions forced NLF leadership to remain mobile and well camouflaged.

MACV and the Joint Chiefs of Staff had sought to locate and target COSVN for nearly a decade, given its perceived importance in controlling the war effort. It became an obsession of Richard Nixon, who was advised by Admiral John McCain that its destruction could prove decisive:

The Joint Chiefs of Staff claimed to have located the enemy's headquarters inside Cambodia — what the United States called the Central Office for South Vietnam, or COSVN. The chiefs envisioned it as a "Bamboo Pentagon," concealed beneath the jungle's canopy. They thought that if you could blow up this central headquarters, you could cripple the enemy's capacity to command and control attacks on US forces in South Vietnam. McCain said the United States should destroy it and win the damn war.

In 1965, nearly 400 US warplanes attempted to wipe out COSVN in an aerial attack, but had no effect on the elusive shadow command. Frequent B-52 raids against its headquarters in Memot, Cambodia failed to kill any of its leadership, while insertion of US / ARVN Special Forces teams often resulted in heavy casualties, described as "poking a beehive the size of a basketball". COSVN narrowly avoided capture of its entire headquarters by ARVN and Cambodian forces during the escape of the Provisional Revolutionary Government in 1970, but after an evacuation to new bases further north in Kratie Province, regular NLF operations in South Vietnam were resumed.