Operation Junction City: The Hunt for the Elusive COSVN Begins
On the 22nd day of February 1967, the U.S. Army II Field Force opened up the largest offensive of the Vietnam War, driving through swamps and jungles in search for the secret headquarters of enemy military operations in South Vietnam.
What is known in the U.S. as the Central Office for South Vietnam, or COSVN, consisted of two parallel organizations set up by the Central Committee of the Labor Party of Vietnam, as the Hanoi-based Communist Party of Vietnam referred to itself. Their mission was to direct the struggle in South Vietnam against the American-backed government in Saigon. No COSVN permanent physical infrastructure was ever discovered or claimed by first-hand sources to have existed. This "Pentagon in the jungle" was constantly on the move, in order to avoid being wiped out.
Operation Junction City took place in War Zone C, a roughly triangular region flush with the Cambodian border, pointing at Saigon from the northwest. War Zone C was a common infiltration point for North Vietnamese forces and materiel entering South Vietnam from the Ho Chi Minh Trail. The COSVN headquarters was believed to be in this region and was believed by some to be housed in a permanent physical headquarters complete with full-time office staff.
Map from "Cedar Falls - Junction City: A Turning Point", Department of the Army, 1989
More than 25,000 men, including two South Vietnamese marine battalions, were committed to the opening day of this operation. More than 5,200 troops, carried by a fleet of 250 helicopters, executed a massive airborne assault along the Cambodian border. An American paratroop battalion made the first combat jump of the Vietnam War, penetrating War Zone C for the first time since the U.S. entered the conflict. It turned out to have been the only mass jump of the Vietnam War.
The guiding strategy was to attempt to seal off a potential escape route into Cambodia with American troops, then drive towards those forces with armored units, completing a "hammer and anvil" maneuver.
During the first 48 hours of combat, only scattered sniper fire was encountered. The Viet Cong were to suffer significant losses over the course of that 82-day operation, but COSVN quietly slipped away across the border into Cambodian territory.