The Saigon River makes its way from Cambodia southeast to Saigon, then continues on towards the South China Sea — its final destination. As the river approaches Saigon (now Ho Chi Minh City), the Cu Chi district sits on its right bank and an area that was called by U.S. military men the Iron Triangle is on its left bank. In January 1967, this region became the scene of the largest U.S. ground operation of the Vietnam War: Operation Cedar Falls.
The Tunnels of Cu Chi
The Iron Triangle region was under Viet Minh control throughout the post-1945 French war in Vietnam and was dominated by the National Liberation Front (Viet Cong) throughout America's involvement in Vietnam. Military Assistance Command, Vietnam commander Gen. William C. Westmoreland considered the Iron Triangle a "dagger pointed at the heart of Saigon", since possession of that stronghold put the Viet Cong in position to threaten the South Vietnamese capitol itself.
In their war against the French, the Viet Minh had elaborated on an old network of tunnels and hidden fortifications throughout the region. Following the departure of the French, the tunnel system was expanded into an immense network serving as a base for underground operations against the South Vietnamese government. The tunnel system contained makeshift hospitals, training grounds, storage facilities, military headquarters and more. Viet Cong guerrillas might stay underground for several months at a time.
Hundreds of miles of tunnels were located in the Iron Triangle region, with a special concentration around the town of Cu Chi. Nearby was a former French owned rubber plantation called Ho Bo Woods. The Viet Cong had built an extensive bunker and tunnel network there — in some places the tunnels were three or four levels deep!
Iron Triangle, Hammer and Anvil, Thin Air
Virtually since the beginning of the Vietnam War, the Iron Triangle had been used as a major communist staging ground and rear area which, by 1966, South Vietnamese government officials and military forces dared not enter. General Westmoreland had formulated plans to go on the offensive in 1967, driving People's Army of Vietnam and Viet Cong forces out of South Vietnam's densely populated regions and pushing them into the lightly populated border region. There, U.S. forces could take advantage of their superior firepower.
Earlier efforts to clear the Iron Triangle of the Viet Cong had failed. The planners of Operation Cedar Falls had determined to achieve the complete eradication of enemy sanctuaries and bases of operations in the area. Plans were not limited to an assault on Viet Cong forces and their infrastructure; the area's civilian population was to be evacuated and their homes destroyed. The area was to be defoliated and categorized as a "free-fire zone", which was a special type of area where any individual encountered was presumed to belong to the Viet Cong.
The operation would employ an entrapment maneuver called "hammer and anvil". Numerous attempts at implementing this tactic were made during the years of heaviest U.S. involvement in Vietnam, with consistently disappointing results. In the first stage, blocking positions, or the "anvil", were stealthily positioned along the Saigon River, which formed the southwestern leg of the triangle. In the second stage, armored cavalry and airborne infantry moved as "hammers", sweeping across the triangle from the east and from the north. It was to be an "Iron Triangle" in more ways than one.
As it turned out, the massive assault largely encountered air — the Viet Cong evaded their attackers by either fleeing to Cambodia or by hiding in the complex underground tunnel network. The largest ground operation of the Vietnam War was characterized by small unit actions and not by large scale combat.
Tunnel Rats: Specialists in a New Type of Warfare
Operation Cedar Falls saw the introduction of the “tunnel rats”, an elite group of volunteers specializing in the art of tunnel warfare. Armed only with a pistol, a knife, a flashlight and a piece of string, these specialists would enter a tunnel alone and cautiously advance inch-by-inch, watching for booby traps or Viet Cong lying in wait. Although American ground forces failed to locate and destroy significant assemblies of enemy forces, the tunnel rats did uncover parts of the secret tunnel system and uncovered the Viet Cong district headquarters at Cu Chi. There they discovered half a million military documents, among which were documents on strategy, maps of U.S. bases, accounts of guerrilla force movements from Cambodia into Vietnam, and lists of South Vietnamese political sympathizers. After being searched to the extent possible, tunnel complexes were rendered useless by means of gas and demolition charges.
The Tunnels of Cu Chi: A Harrowing Account of America's Tunnel Rats in the Underground Battlefields of Vietnam provides first-hand accounts from brave souls on both sides of the conflict who waged tunnel warfare.
Operation Cedar Falls: A Disappointing Outcome
Although the National Liberation Front was dealt a setback, it quickly reestablished authority over the Iron Triangle area. Only a year following the operation's conclusion, the area was used as a staging ground for Tet Offensive attacks on Saigon. Compounding the lack of lasting results with negative aftereffects, measures such as saturation bombing and the forced relocation of civilian populations created a legacy of ill will towards the U.S.