As advisor to President John F. Kennedy, then national security advisor (1969-75) and secretary of state (1973-77) to President Richard Nixon, Henry Kissinger was responsible for making major decisions related to the Vietnam War. He kept the U.S. bombing of Cambodia a secret from Congress, but won the Nobel Prize for negotiating the 1973 Paris Peace Accords that led to a ceasefire. That peace failed two years later.

His flair for secret diplomacy earned him both acclaim and detractors, but the legacy of Vietnam, which he called “a tragic national experience,” haunted him long after the war.

In his book, Ending the War in Vietnam, Kissinger depicts himself as being “drawn into the vortex” of the Vietnam War, going from someone “who had met the President-elect only once and then only for a few minutes” to becoming “the principal adviser to the president on the policy for the extraction from Vietnam and eventually the chief negotiator.” His closeness with Nixon was his initial source of power. It was also the tie that led to his downfall.

The Vietnam War was a central issue in the 1968 presidential election, and Nixon campaigned on the promise to bring “peace with honor.” The unpopular war begun under Kennedy and Johnson as a way to stop communism from spreading in Southeast Asia was costing taxpayers an annual $30 billion. Two hundred out of the 500,000 Americans stationed in Vietnam were dying every week, fueling even more protest against the draft. But to pull out of the conflict meant abandoning American allies in South Vietnam and, Kissinger and Nixon feared, make America look weak.

“Kissinger, like Nixon, distrusted Cold War bureaucracy,” says Robert. K. Brigham, Shirley Ecker Boskey Professor of History and International Relations at Vassar and author, Reckless: Henry Kissinger and the Tragedy of Vietnam. Nixon circumvented the state department and the foreign service by granting Kissinger permission to conduct secret negotiations with the North Vietnamese.

“Nixon wanted his own man doing his negotiations so the credit for ending the war would come to him, not the State or Defense Department,” says Thomas Alan Schwartz, director of Undergraduate History Studies at Vanderbilt University and author, Henry Kissinger and American Power. What Nixon didn’t anticipate was Kissinger’s ability to eclipse his boss: “He created his own Frankenstein monster in Kissinger,” says Schwartz.

A tiny villa outside Paris was the unlikely setting for Kissinger and North Vietnamese representative Le Duc Tho to discuss terms for peace. They met a total of 68 times, with Kissinger keeping certain conversations secret even from the President, says Brigham. “Kissinger wanted to make sure the war ended in Paris and not in Saigon. He had very little faith in the Vietnamese armed forces. He understood U.S. Congress didn’t have stomach for the conflict and wanted the U.S. to withdraw without looking like it was an overwhelming defeat,” Brigham says.

The Paris Peace accords leading to a ceasefire in Vietnam were signed on January 27, 1973. To critics, “peace with honor” didn’t look that different from options available when Nixon first took power: “Kissinger and Nixon wasted four years of negotiations with the Vietnamese communists, agreeing to virtually the same peace terms in 1973 that were on the table in 1969,” argues Brigham. In total, 2.5 million to 3 million Vietnamese and other Indochinese and 58,000 Americans died in Vietnam. Hundreds more were missing in action.

In October, Kissinger and Le Duc Tho were named the joint recipients of the Nobel Peace Prize. Only Kissinger accepted; Tho refused the award until “peace is truly established.”

While Nixon publicly favored a policy of Vietnamization, or the withdrawal of U.S. troops so that the South Vietnamese could take over military operations, he secretly escalated the Vietnam War by bombing neighboring Laos and Cambodia. The North Vietnamese transported supplies and arms across the borders of their officially neutral neighbors, and Kissinger saw bombing them as a way to put pressure on Hanoi.

Kissinger was deeply involved in the bombing raids on Cambodia—and in keeping them a secret from Congress and the public. According to a Pentagon report released in 1973, “Henry A. Kissinger approved each of the 3,875 Cambodia bombing raids in 1969 and 1970” as well as “the methods for keeping them out of the newspapers.”

By the end of the bombing campaign, nicknamed “Operation Menu,” the U.S. had dropped a total of 110,000 tons of bombs that killed between 150,000 and 500,000 civilians. The Khmer Rouge galvanized anti-American sentiment in a destabilized Cambodia, rising to power and slaughtering 1.7 to 2.2 million Cambodians as part of the Cambodian genocide.

In 1973 and 1974, a Gallup poll declared Kissinger “the most admired man in America.” The acclaim was short-lived. The Watergate scandal that led to Nixon’s resignation revealed that Kissinger had ordered the FBI to wiretap the phones of members of the National Security Council to see who had leaked news of the U.S. bombing of Cambodia to the press. By 1975, the communist victory in Vietnam had tarnished the legacy of his 1973 peace efforts.

Though he continued to be a major player in global diplomacy, Vietnam cast a shadow over Kissinger’s career. “The ironic legacy is that Kissinger received the Nobel Peace Prize for his work in the Vietnam War—not a war he ended—and not for the Middle East, the war he did," says Schwartz. "The war he failed in was the war he was acknowledged for."