With the goal of clearing dangerous communist concentrations north of Saigon, American forces launched Operations Cedar Falls (January 8-26, 1967) and Junction City (February 22 –May 14, 1967), arguably the largest American operations in the Vietnam War, in early 1967. After a prolonged period of building up American forces and shoring up the South Vietnamese defenses, Gen. William C. Westmoreland, the American commander in South Vietnam, could take the offensive.

By October 1966 American forces in South Vietnam had risen to 351,600; South Vietnamese forces numbered 735,900, and Allied forces from other nations numbered 32,600. Communist forces (both North Vietnamese and Viet Cong) in South Vietnam numbered about 131,000 conventional troops, 113,000 militia and 39,000 political cadre. 

Westmoreland believed the dry season (November – May) would be the best time for an offensive to sweep War Zone C, in Tay Ninh Province, to the Cambodian border. First, troops had to face the “Iron Triangle”, a three hundred square kilometer knot of difficult terrain thirty kilometers north of Saigon. Here the communists had established a deeply dug in base area, and were capable of launching forays into Saigon. The operation to liquidate the Iron Triangle would be called Cedar Falls, and the subsequent sweep of War Zone C called Junction City.

The Iron Triangle featured extensive underground tunnel complexes constructed over the years, the most significant of which was at Ben Suc. The 1^st Battalion 26^th Infantry seized Ben Suc with a masterful helicopter-borne air assault on January 8, 1967. Meanwhile the 25^th Infantry Division sealed off the west side of the triangle, and the 1^st Infantry Division, 173rd Airborne Brigade and 11^th Armored Cavalry Regiment swept into it from the north and east. Despite formidable defenses, the communists lost 700 dead and 700 captured. Perhaps more consequential, the Americans destroyed 1,100 bunkers, 400 tunnels and 500 other structures, and captured 3,700 tons of rice, 491,553 pages of documents, over 600 weapons, and tons of munitions.

Cedar Falls saw the first general introduction of “tunnel rats”—soldiers  with modest statures and quick reactions who volunteered to take the battle underground. Armed with probes, flashlights, compasses, field phones and pistols, they searched enemy tunnels and mapped the tunnels as they went. They stretched telephone wire behind them to guide them back. Fierce battles broke out in the subterranean darkness. When sufficient information had been gathered, the Americans used explosives and acetylene gas to blow up the tunnels.

With the Iron Triangle secure, Westmoreland moved on to Junction City. In 82 days of intermittent fighting the Americans further devastated communist logistics. The communists lost 2,728 killed to 282 for the Americans. The Americans captured tons of rice and ammunition and thousands of pages of documents. They methodically cleared War Zone C, and bloodily repulsed communist counter- attacks. Surviving communist units and headquarters slipped across the border into Cambodia. From sanctuaries in Cambodia the communists sought to control the timing and nature of subsequent operations, thus avoiding prolonged exposure to the superior American forces.

More than 2,500 Americans who lost their lives in the Vietnam War and were missing in action are commemorated on the Courts of the Missing at the Honolulu Memorial.

Recommended Reading

MacGarrigle, George L., Combat Operations: Taking the Offensive, October 1966 to October 1967 (Washington DC: U.S. Army Center of Military History, 1998)

Rogers, Lieutenant General Bernard W., Cedar Falls – Junction City: A Turning Point (Washington DC: U.S. Army Center of Military History, 1989)

Stewart, Richard W., American Military History: The United States Army in a Global Era, 1917-2003 (Washington DC: U.S. Army Center of Military History, 2005)