The senior Viet Cong commander inside the Iron Triangle received word of Operations Cedar Falls as soon as the South Vietnamese did. When the incredulous John Paul Vann and the USAID were receiving the briefing from the II Corps staff on 7 January, the VC commander had made the decision not to fight. In less than 24 hours, five of his nine battalions had already escaped north toward Cambodia (they were out before the 1st ID hammer landed) or southeast through the Cu Chi tunnels toward Saigon. Two battalions attempted to escape west and were effectively destroyed by 2nd Brigade, the 25th Infantry Division. The other two battalions went into the extensive tunnel systems and either waited for the 11th ACR to pass overhead, or they fought it out in the numerous small unit actions over the next two weeks. Most casualties from the operation were the result of the booby traps and small ambushes, many inside the tunnels.
After the civilians of Ben Suc and the hamlets were evacuated, the Americans went after the tunnel system with a vengeance. American volunteers, called “tunnel rats”, delved downward and engaged the VC with pistols, knives, and flashlights. To their astonishment, they caught a glimpse of how deep and extensive the tunnels actually were, and the futility of trying to clear them. Tunnel Rats were not new in the war, but where before they were just volunteers with giant brass gonads, Cedar Falls was the first time they were specially trained and organized. When they deemed it impossible to go further, engineers above would flood the tunnels with acetylene gas, light it, then bull dozers would collapse the tunnels and seal them off. For good measure, B-52 strikes would be called on the more extensive and deeper systems to collapse them, which it was found out later was the only real way of damaging them permanently, and then only when the bombs fell directly above.
Operation Cedar Falls was a body blow to the VC. Publicly the Communists declared it failure, just as Saigon declared it a victory. But by the American’s own metrics it was not nearly what Seaman was hoping for: the body count was relatively low, just 753 or just under two battalions. 507 VC defected under the Chieu Hoi program, though many disappeared later. Thousands of tons of rice were seized but few weapons and ammunition. The big haul was intelligence, though Westmoreland couldn’t say that on the air. Over 500,000 documents and the majority of the COSVN headquarters support staff were captured (the “primaries” and the important members of the staff moved to the Fishhook in Cambodia in December. Cedar Falls interrupted the movement of the remainder). The new found intelligence painted a far different picture than what the Americans or South Vietnamese had thought to be true.
It took the first half of 1967 to translate and analyze the document and interrogation haul from Cedar Falls. And Westmoreland and Saigon couldn’t believe what they saw. The insurgency was so deeply entrenched that VC shadow governments operated alongside the South Vietnamese at every level. Many South Vietnamese Army units had truces with the VC in their districts. The documents painted a picture of an insurgency that was clearly winning, and whose district and provincial leadership were unafraid of having their names and activities recorded. The haul provided targeting fodder for thousands of Phoenix Program operations and quickly resulted in the expansion of CORDS. In the end the document dump probably sank Westmoreland. Although Westmoreland brilliantly saved Vietnam from being overrun in 65, and then miraculously built up the US conventional offensive presence nearly from scratch then fought Giap and Than to a standstill in 66, President Johnson and Secretary McNamara no longer believed what Westmoreland was feeding them. Even money says it led directly to the decision to replace him in late 1967.
The intelligence windfall was not lost on Giap. He was furious at Than and would hold it against him until his rival’s “accidental” death later in the year. Operation Cedar Falls proved that the VC in South Vietnam were not ready for main force operations against the Americans, though it would take another American operation to confirm it. Giap and Than wouldn’t have long to wait.
On 26 January 1967, just 18 days after LTC Haig and his battalion landed around Ben Suc, the last Americans and South Vietnamese pulled out of the Iron Triangle to prepare for the next corps level search and destroy operation. Despite the severe damage to the tunnel system and a dozen square miles of jungle defoliated, the first VC moved back in just ten days later; the first civilians, two weeks later.
The Iron Triangle would continue as a VC safe haven for another three years.