President Richard M. Nixon made a disastrous decision to widen the Vietnam War by invading Cambodia, recounted here in an excerpt adapted from my new book, One Man Against the World: The Tragedy of Richard Nixon. We are watching the story repeat itself today. From the Middle East to Afghanistan, the United States is ever more enmeshed in wars with dubious friends and elusive enemies. – Tim Weiner

Nixon suffered from demonic insomnia. “I don’t think he ever slept,” said General Alexander M. Haig, then deputy assistant to the president. Nixon dealt with it at night by drinking. By day, he fell into a dark state of portents and omens. Talking with White House Chief of Staff H.R. Haldeman, Nixon suddenly started planning the precise details of his own funeral.

The president’s popularity was plummeting. The endless war in Vietnam was the cause. The war’s toll was measured not only by hundreds of Americans who died each week, but in wounds of the mind: soldiers who became shell-shocked or heroin-addicted in Vietnam. They returned to find the war had come home with them, a battle within the American body politic.

On Mar. 19, 1970, Nixon’s national-security adviser, Henry Kissinger told a trusted colleague about a brutal telephone conversation he had just held with the president. Kissinger told Nixon that “there wasn’t much we could do militarily” to force North Vietnam to settle or surrender. The president “went through the roof.” He demanded a new set of war plans — a “hard option” — and he wanted it that day. Kissinger became frantic. The nation’s military and intelligence chiefs had no hard options or new ideas.

Then, suddenly, came a coup out of nowhere: a right-wing military junta took power in Cambodia. In reaction, battle-hardened North Vietnamese forces started moving toward the Cambodian capital, Phnom Penh, 200 miles northwest of U.S. military headquarters in Saigon.

The Cambodian army was hopeless — “totally unprepared for combat,” according to a recently declassified U.S. military history. “It lacked experienced leaders, corruption was prevalent among its officers and pay was low.” Its principal activity in the past decade had been draining swamps. A clash between these mismatched armies was certain. Cambodians and Vietnamese had hated one another — politically, tribally, racially — for centuries.

Nixon instinctively embraced the right-wing Cambodian coup leader, a general no one knew well but with a name no one could forget: Lon Nol.

“President Nixon asked me to draft several personal Nixon-to-Lon Nol telegrams containing rather extravagant expressions of friendship and support,” recalled Marshall Green, assistant secretary of state for East Asia. “I was concerned that Lon Nol would read into these messages a degree of U.S. military support and commitment that exceeded what our government could deliver. … I also regarded Lon Nol as lacking the qualities needed to lead his country out of its mess.”

As the mess deepened in Cambodia, Nixon ordered the CIA into the fight. “I want [CIA director Richard] Helms to develop & implement a plan for maximum assistance to pro-U.S. elements in Cambodia,” he instructed Kissinger in writing.

That meant untraceable money and guns, preferably Swiss gold and an arsenal of Communist-bloc weapons such as AK-47 assault rifles, which the Cambodians could claim they had captured from the Vietcong.

The CIA director promised to support Nixon’s “military effort against the Viet Cong in Cambodia . . . by the provision of covert economic and political support.” This proved difficult in the short run. Cambodia, with no U.S. ambassador, no CIA station chief and no CIA or military intelligence officers on the ground, was terra incognita as a war zone. The U.S. embassy was in the hands of a few Foreign Service officers — diplomats, not warriors.

Helms decided to call in John Stein, a veteran CIA officer with plenty of paramilitary experience in Africa, but none in Indochina. Stein reported back to the CIA and the White House shortly after he arrived in Cambodia. He got straight to the point: “Here was another small Southeast Asian country where nobody knew what was going on.” The new Cambodian regime “had come to the conclusion that somebody had to help them, and that this somebody was the U.S. With more fighting on their hands, their morale needed bucking up. The only way at the moment to give this bucking up was to give the AK-47 package and provide a Swiss bank account.”

Nixon approved 1,500 assault rifles and $10 million in untraceable CIA cash for Lon Nol, a down payment on a far greater commitment coming soon.

* * *

That same week, North Vietnamese soldiers laid deadly siege to America’s central outpost in Laos, the CIA’s mountain redoubt in Long Tieng. If it fell, Laos could collapse into chaos or face the threat of Communist control. The crisis demanded action but offered no easy solution. Kissinger had to plead for the president’s attention.

“Poor K,” Haldeman noted sardonically in his Mar. 24 diary entry, “no one will pay attention to his wars, and it looks like Laos is falling.”

On Mar. 25, Nixon met for three hours with Kissinger, Helms and key National Security Council members. The president, Kissinger noted drily, wasn’t inclined to let Laos go down the drain. Helms was blunt: Washington had to ask the right-wing military junta in Thailand to send battalions of troops into Laos, widening the covert war without telling Congress.

The next afternoon, Kissinger called Nixon, who was in Key Biscayne at the start of a four-day Easter weekend. “The Thai battalion, are we going to get them in there?” Nixon asked. “That’s done,” Kissinger replied.

“There’s going to be no announcement,” the president said. “We are just going to do it. We don’t have to explain it.” With that, Nixon tried to take his mind off life-and-death issues. He spent the next three days sailing, sunbathing and drinking in Key Biscayne and the Bahamas with his friend Bebe Rebozo.

Kissinger sent an attention-getting intelligence report to Key Biscayne on Friday morning, Mar. 27: North Vietnam had placed its military forces on alert in Cambodia. Nixon’s immediate response was to order the Air Force to step up the bombing of Communist targets in Cambodia. His nightmare was that Cambodia would fall, providing a permanent base for the North Vietnamese armed forces. If Laos fell, too, U.S. soldiers would face Communist forces on three fronts.

The American Embassy in Saigon could become a garrison encircled by Asian guerrillas. The United States, with all its military might, could lose the war. All that, and worse, would come to pass as a consequence of Nixon’s strategies.

* * *

On April 4, 1970, Kissinger reconvened his secret negotiations in Paris with North Vietnam’s Le Duc Tho, who grasped Washington’s strategic problems as acutely as Kissinger and described them with greater accuracy.

“We have no intention of using Laos to put pressure on you in North Vietnam,” Kissinger falsely asserted. The CIA and its Lao tribesmen were running cross- border sabotage attacks into North Vietnam at that very moment. “As for Cambodia, we have no intention of using Cambodia to bring pressure on Vietnam.” That, too, was a falsehood.

Le Duc Tho responded: “This does not conform with reality. … While you are suffering defeat in Laos and Vietnam, how can you fight in Cambodia? You have sowed the wind, and you must reap the whirlwind.”

By April 19, the Communists were 20 miles from the Cambodian capital of Phnom Penh. Nixon, in Hawaii to greet the astronauts returning from the nearly fatal Apollo 13 moon mission, was briefed by Admiral John McCain, the commander in chief for the Pacific, whose son (now a senator) was a prisoner of war.

McCain captivated Nixon with a hair-raising report. The president ordered the admiral to return with him to the Western White House in San Clemente, California, on April 20 and meet with Kissinger. McCain’s briefing was grim: If the Communists took Cambodia, South Vietnam might be next, and the war would be lost. He said Washington should send every weapon it could find to Phnom Penh, South Vietnam’s troops should attack across the Cambodian border and squadrons of B-52s should bombard the Communists.

The Joint Chiefs of Staff claimed to have located the enemy’s headquarters inside Cambodia — what the United States called the Central Office for South Vietnam, or COSVN. The chiefs envisioned it as a “Bamboo Pentagon,” concealed beneath the jungle’s canopy. They thought that if you could blow up this central headquarters, you could cripple the enemy’s capacity to command and control attacks on U.S. forces in South Vietnam.

McCain said the United States should destroy it and win the damn war.

Nixon’s meeting with McCain in the Western White House gardens was a fatal turning point. U.S. boots were about to hit the ground in the bomb-cratered wastelands of eastern Cambodia.

Nixon, Kissinger and McCain “discussed possible cross-border attacks into Cambodia,” reads a unique account in a recently declassified Joint Chiefs history. “If such operations were mounted, the president asked, what would be the best mix of U.S. and South Vietnamese forces? Or should only [South Vietnamese] troops be used, with the United States furnishing air and artillery support from within South Vietnam? Admiral McCain assured the president that plans were being prepared on an urgent basis and would be submitted to the Joint Chiefs of Staff as quickly as possible.”

The United States quickly assembled tons of weapons for the Cambodian army. It scoured the arms depots of every U.S. ally in Asia and dealt in black markets to procure ammunition. U.S. military officers in Saigon assembled an arsenal for 10,000 soldiers — carbines, pistols, machine guns, rocket launchers and mortars.

That was the easy part. Now the president needed a plan for the invasion of Cambodia and the destruction of the central command.

But Nixon never understood that COSVN was not a place. It had no address. It was a small mobile group of Communist officers, located only by the radio signals they transmitted. Yet even that location was fixed by the antennae they used for transmissions, which could be miles away from the men doing the talking.

And the enemy always seemed to know when the B-52s were coming. North Vietnam’s intelligence on U.S. intentions was far better than American intelligence on its enemy’s plans.

* * *

Nixon did not sleep for more than an hour or two on April 21. He dictated a disturbing note to Kissinger: “I think we need a bold move in Cambodia, assuming that I feel the way today (it is 5 a.m., April 22) at our meeting as I feel this morning to show that we stand with Lon Nol. I do not believe he is going to survive. There is, however, some chance that he might and in any event we must do something.”

The meeting was a National Security Council conclave. Nixon demanded that no staff attend and that no one take notes. But General Earle Wheeler, chairman of the Joint Chiefs of Staff, and Admiral Thomas Moorer left detailed accounts in the Joint Chiefs’ files.

At the meeting, Nixon immediately authorized large cross-border attacks by South Vietnam into Cambodia, with support from U.S. artillery and fighter jets. He said that he had not yet decided the question of American ground forces.

The war council was split three ways. Defense Secretary Melvin Laird and Secretary of State William Rogers argued for a limited incursion, conducted by South Vietnamese troops. Kissinger favored an attack on the two Cambodian sanctuaries, in areas called the Parrot’s Beak and the Fishhook — but without U.S. ground troops. The military wanted an assault on the Communists in Cambodia and the spectral COSVN headquarters, with U.S. soldiers leading the charge. So did Vice President Spiro T. Agnew, who objected to “all the pussyfooting.”

Nixon resented the implication that he was not being tough enough. He decided to go for an all-out attack with U.S. ground forces.

The Joint Chiefs of Staff never drew up a formal plan for the Cambodian operation. There wasn’t time. But three of Kissinger’s most loyal National Security Council staff members — Winston Lord, Tony Lake and Roger Morris — knew of the coming invasion. They warned Kissinger that it would create “a political storm here, as it would be the most shocking spur to fears of widening involvement in U.S. ground combat in Southeast Asia.” Lake and Morris resigned in protest. Lord stayed on and was rewarded for his loyalty.

At 7:20 a.m. on April 24, Nixon, after another sleepless night, summoned Kissinger, Moorer and Helms to the White House. In a fury, the president said that Rogers and Laird were sabotaging plans for the invasion. “P is moving too rashly without thinking through the consequences,” Haldeman noted in his diary that evening. Kissinger called Helms to ask him what he thought of Nixon’s decisions.

Helms replied, “It seemed to me that if he is prepared for the fallout, then it is the thing to do. He obviously was.”

“It is worth it?” Kissinger asked. Helms hoped so.

* * *

On April 30, 1970, after another night with one hour of sleep, the president went on television to announce the invasion of Cambodia.

“This is not an invasion of Cambodia,” he said, a classic Nixon contradiction.

“My fellow Americans, we live in an age of anarchy, both abroad and at home. We see mindless attacks on all the great institutions which have been created by free civilizations in the last 500 years. Even here in the United States, great universities are being systematically destroyed. Small nations all over the world find themselves under attack from within and from without.

“If, when the chips are down, the world’s most powerful nation, the United States of America, acts like a pitiful, helpless giant, the forces of totalitarianism and anarchy will threaten free nations and free institutions throughout the world.”

Rogers was in his hideaway office on the State Department’s seventh floor that night. As Nixon concluded his speech, he snapped off the TV set and said: “The kids are going to retch.”

The nation’s college campuses exploded in protest. National Guardsmen shot and killed four youths at Kent State University in Ohio. More than 100,000 demonstrators prepared to march on Washington.

“The Cambodian incursion was an unmitigated disaster,” begins a National Security Agency history of the battle, declassified in 2013. “American bombs tore up miles of jungle and troops floundered through a trackless quagmire” in fruitless pursuit of the Bamboo Pentagon.

Cambodia eventually fell to the murderous Khmer Rouge, who killed a quarter of its population between 1975 and 1979.

That was part of Nixon’s legacy — one more lost battle in his desperate search for “peace with honor” in Vietnam, which led to the deaths of more than 20,000 U.S. soldiers during his presidency, a dishonorable retreat and victory for the enemy.

Excerpted from One Man Against the World: The Tragedy of Richard Nixon by Tim Weiner, published by Henry Holt and Company, LLC. Copyright (c)2015 by Tim Weiner. All rights reserved.