The Tet offensive, which began 50 years ago today and is remembered as the turning point of the Vietnam War, caught Americans by surprise. One of the few who saw what was coming was Edward Lansdale, the legendary covert operative and retired Air Force general who had helped to create the state of South Vietnam after the French withdrew. He had returned to Saigon in 1965 as an official at the American Embassy, trying to use his close ties to the South Vietnamese to salvage something from a failing war effort.

At a time when many American leaders were cautiously optimistic about the war, at least in public, Lansdale was sending up warning flares. At the end of October 1967, he wrote to Ellsworth Bunker, the ambassador to Saigon, “I believe that Hanoi is gambling on the climax of the war coming in 1968.” He anticipated that North Vietnam’s leaders would try to repeat their success against the French: “Hanoi policymakers and historians saw the defeat of the French forces as having reached its decisive point through the antiwar sentiment in Metropolitan France rather than on the field of battle in Vietnam; Dien Bien Phu was fought by the Viet Minh mostly to shape public opinion in Paris, a bit of drama rather than sound military strategy. It worked.” Now, he warned, Hanoi was going to implement a similar plan to “bleed the Americans” and “get the American public to force U.S. withdrawal,” because “they believe the American public is vulnerable to psychological manipulation in 1968.”

It was an uncannily accurate prediction, but like much of what Lansdale had to say, it went unheeded by the powers that be. He had warned in 1963 that it was a mistake to overthrow his friend and protégé, President Ngo Dinh Diem. He was ignored, and after Diem’s death in a military coup, South Vietnam went into free fall, leading Lyndon Johnson to send American troops into combat to avert a Communist victory. Then Lansdale had warned that there was no way out of the quagmire through military action alone; the United States, he said, had to nurture a legitimate government in Saigon that could win the support of the people. He had been ignored again as America opened a Pandora’s box of free-fire zones and search-and-destroy missions. Gen. William Westmoreland was convinced he could kill the Vietcong faster than they could be replaced.

The Tet offensive, which unfolded over Jan. 30 and 31, 1968, exposed Westmoreland’s blithe assurances, as late as the fall of 1967, that he saw a “light at the end of the tunnel” as little more than wishful thinking. Eighty thousand Vietcong troops attacked 36 of 44 provincial capitals, 64 of 242 district capitals, five of six autonomous cities and numerous hamlets and villages. A battle for control of Hue, the old imperial capital, raged for more than a month. Even the perimeter of the embassy in Saigon was penetrated by a Vietcong sapper squad.