The visit to Vietnam of CBS Evening News anchor Walter Cronkite in February 1968 and his commentary expressing doubts about victory in the war was the dagger to the heart of Lyndon Johnson’s presidential reelection bid. Approval ratings of the war effort dropped below 50 percent, and as a result, the insurgent Democratic candidate and senator Eugene McCarthy came close to pulling an upset over Johnson in the New Hampshire primary.

Johnson, who had produced a stunning array of legislative accomplishments in civil and voting rights following John Kennedy’s assassination, had in effect presided over what would be the final year of America’s post-World War II triumphalism. It had been an ascending period of U.S. global leadership and dominance, which made New York the commercial capital of the world, Washington the epicenter of global military power and diplomatic influence, and America the ubiquitous bulwark against communism.

{mosads}In late March 1968, as the Wisconsin primary approached, Johnson was trailing badly in the polls and stunned the nation by withdrawing from the presidential race. That was followed just a few days later by an enormous racial tsunami on April 4, 1968 with the assassination of Martin Luther King Jr.

I can still vividly recall standing transfixed outside the State Department training center in Arlington, as huge plumes of black smoke rose out of our burning national capital, which had not experienced such a widespread conflagration since the War of 1812. In an extraordinary midday rush hour, cars filled with government employees and business people fled across the Key Bridge, carrying with them the remnants of a decade of improved race relations.

That weekend when the fires had been put out and order restored by units of the 82nd Airborne Division flown in from North Carolina, I drove into Washington and observed the results of the rage that the tragic murder of King had unleashed. The sight of burned buildings and helmeted soldiers carrying rifles with fixed bayonets on every street corner remains with me to this day.

It was then, in the midst of the charred ashes of American political unity, that Robert Kennedy stepped to center stage. Carrying the mantle of Camelot, he seemed to offer the chance to restore the ascendancy of the new frontier and the justice his brother Jack had pledged to African Americans. It seemed that the triumphalism of post-World War II America that President Kennedy had symbolized could be restored.

Then, in a hotel ballroom, that last chance for redemption was shattered forever on June 5, 1968 by an assassin’s bullet that took Bobby Kennedy’s life and with it the possibility of restoring political tranquility to the nation. Anti-war protests, demonstrations in inner cities, and turmoil at the Democratic National Convention in Chicago produced harsh responses by law enforcement and left the political process convulsed.

Watching the hearse carrying Bobby Kennedy’s body cross Memorial Bridge to Arlington National Cemetery, I recall feeling an incredible sense of depression about the future of the country. Ten months after the Tet Offensive, as I boarded a plane to fly to Saigon and my assignment in the Mekong Delta, our country and our politics, race relations and the war effort would once again be forever changed in a manner not dissimilar to the Civil War.

With the election of Richard Nixon later that year and the beginning of Vietnamization, it was clear that the United States was no longer trying to win the war. It was only trying to find a way out. In that situation, as part of the Military Assistance Command in Vietnam, I witnessed the attitude of “no one wanting to be the last person to die in Vietnam” spread through the U.S. Army, eroding discipline and morale, especially among draftees, and leading to the “fragging” of officers who were too aggressive.

While Nixon’s election can be seen as temporarily providing a respite to the political turmoil that had, like a Midwest tornado, swirled the nation uncontrollably, events over the next few years continued to keep tensions high. The killings at Kent State, the Cambodian incursion, and eventually Watergate left America exhausted, divided, and without the will to continue the Vietnam struggle.

The ignominious disgrace of the evacuation of Saigon in April 1975, with the American ambassador fleeing the advancing North Vietnamese Army, was the final blow against American triumphalism. It was the culmination of incredible political upheaval, all of which began of Jan. 30, 1968, when the Viet Cong blew their way into the U.S. Embassy.

It would become the very same building from which, seven years later, the helicopter would take off carrying Ambassador Graham Martin and with him the tattered remnants of America’s reputation as a dependable ally and a bulwark against communism, as well as the sense that triumphal America could do anything.

Kenneth Quinn is president of the World Food Prize Foundation. He served as U.S. ambassador to Cambodia and spent more than 30 years as a foreign service officer with the U.S. State Department.