Twelve helicopters, bristling with guns and U.S. Marines, breached the morning horizon and began a daring descent toward Cambodia's besieged capital. The Americans were rushing in to save them, residents watching the aerial armada believed. But at the U.S. Embassy, in a bleeding city about to die, the ambassador wept.

Forty years later and 6,000 miles away, John Gunther Dean recalls what he describes as one of the most tragic days of his life — April 12, 1975, the day the United States "abandoned Cambodia and handed it over to the butcher."

Time has not blunted the former ambassador's anger, crushing shame and feelings of guilt over what also proved a milestone in modern American history — the first of several U.S. interventions in foreign countries climaxed by withdrawals before goals were accomplished and followed by often disastrous consequences.

"We'd accepted responsibility for Cambodia and then walked out without fulfilling our promise. That's the worst thing a country can do," he says in an interview in Paris. "And I cried because I knew what was going to happen."

Five days after Operation Eagle Pull, the dramatic evacuation of Americans, the U.S.-backed government fell as communist Khmer Rouge guerrillas stormed into Phnom Penh. They drove its 2 million inhabitants into the countryside at gunpoint, launching one of the bloodiest revolutions of modern times. Nearly 2 million Cambodians — one in every four — would die from executions, starvation and hideous torture.

Many foreigners present during the final months — diplomats, aid workers, journalists — remain haunted to this day by Phnom Penh's death throes, by the heartbreaking loyalty of Cambodians who refused evacuation and by what Dean calls Washington's "indecent act."

I count myself among those foreigners, a reporter who covered the Cambodian War for The Associated Press and was whisked away along with Dean and 287 other Americans, Cambodians and third-country nationals. I left behind more than a dozen Cambodian reporters and photographers — about the bravest, may I say the finest, colleagues I've ever known. Almost all would die.

For the general public, the pullout is largely forgotten, overshadowed by the mass, hysteric flight from Saigon and the end of the Vietnam War three weeks later. But for historians and political analysts, the withdrawal from Cambodia signifies the first of what then-U.S. Secretary of State Henry Kissinger termed "bug-outs."

"It was the first time Americans came anywhere close to losing a war. What worries me and many of us old guys who were there is that we are still seeing it happen," says Frank Snepp, a senior CIA officer in Saigon and author of "Decent Interval," which depicts the final years of the Vietnam War. After Cambodia and Vietnam came Laos; there would be other conflicts with messy endings, like Central America in the 1980s, Iraq and — potentially — Afghanistan.

Today, at 89, Dean and his French wife reside in a patrician quarter of Paris, in an elegant apartment graced by statues of Cambodian kings from the glory days of the Angkor Empire. A folded American flag lies across his knees, the same one that he clutched under his arm in a plastic bag as he sped to the evacuation site. Captured by a photographer, it became one of the most memorable images of the Vietnam War era.

In the apartment's vestibule hangs a framed letter signed by President Gerald R. Ford and dated Aug. 14, 1975. It highlights that Dean was "given one of the most difficult assignments in the history of the Foreign Service and carried it out with distinction."

But Dean says: "I failed."

"I tried so hard," he adds. "I took as many people as I could, hundreds of them, I took them out, but I couldn't take the whole nation out."

The former ambassador to four other countries expresses more than guilt. He is highly critical of America's violation of Cambodian neutrality by armed incursions from neighboring Vietnam and a secret bombing campaign in the early 1970s which killed thousands of civilians and radicalized, he believes, the Khmer Rouge. Once-peaceful Cambodia, he says, was drawn into war for America's interests, a "sideshow" to Vietnam.

The U.S. bombed communist Vietnamese sanctuaries and supply lines along the Vietnam-Cambodia border, keeping Cambodia propped up as an anti-communist enclave, but it provided World War II aircraft and few artillery pieces to Phnom Penh forces fighting the Khmer Rouge.

"The U.S. wasn't that concerned about what happened one way or the other in Cambodia but only concerned about it to the extent that it impacted positively or negatively on their situation in Vietnam," says Stephen Heder, a Cambodia expert at London's School of Oriental and African Studies.

Opinion on what went wrong in Cambodia remains split to this day. One view is that the country was destabilized by the American incursions and bombings; another is that Washington failed to provide the U.S.-propped Lon Nol government with adequate military and other support.

In his memoirs, Kissinger says the U.S. had no choice but to expand its efforts into the neighboring country, which the North Vietnamese were using as a staging area and armory for attacks on U.S. troops in South Vietnam. And as Cambodia crumbled, he writes, anti-war elements, the media and Congress combined to tie the administration's hands, preventing further assistance.

Dean is bitter that Kissinger and other power brokers in Washington did not support his quest to persuade ousted Cambodian King Norodom Sihanouk to return from exile and forge a coalition between the Khmer Rouge and Lon Nol. It was Dean's "controlled solution."

"We were also on the telephone with Washington shouting, 'Help us. We are going under. We are going to leave this country unprotected,'" Dean said in earlier oral testimony. But Washington seemed unmoved.

"Ambassador Dean never had (President Richard) Nixon's or Kissinger's support because both of them wanted out of Indochina," Snepp says.

By early 1975, the embassy's cables, most of them declassified in 2006, were becoming increasingly frantic.

Meeting me one day, a haggard Dean, who had lost 15 pounds, asked rhetorically: "Isn't there any sense of human decency left in us?"

"Phnom Penh was surrounded by explosions and a night sky of blossoming flares and streaks of tracer bullets," I wrote in one of my stories at that time. "Children were dying of hunger, the hospitals looked more like abattoirs and the Cambodian army lost as many men in three months as the U.S. did in a decade of war in South Vietnam."

The Khmer Rouge were tightening their stranglehold on the capital, shutting down the airport from which the embassy had flown out several hundred Cambodians. An April 6 cable from Dean said the Cambodian government and army "seem to be expecting us to produce some miracle to save them. You and I know there will be no such miracle."

Congress was cutting the aid lifeline to Phnom Penh. The American public had had enough of the war.

Among Cambodians in the know, some anti-American feeling was growing.

"The Americans give temporary aid but ultimately they think only of themselves. We in Cambodia have been seduced and abandoned," Chhang Song, a former information minister, said one night in early 1975.

But among Phnom Penh residents I found only smiles — "Americans are our fathers," one vegetable vendor told me — along with a never-never-land mindset that things would turn out to be all right. Somehow.

"I honestly believe we did not do enough. There was something better that could have come out other than a genocide of 1.7 million people," Dean says, explaining in part why he, a Jew, felt so strongly. "Now you must understand, I was born in Germany and suffered under Nazi oppression, so how could I turn over a people to the butcher?"

Dean's abiding emotions are shared by others of his former staff.

Alan Armstrong, the assistant defense attache, is still trying to complete a novel to exorcise what he went through. It is called "La Chute," ''The Fall."

"I was paid by my government to smile, break bread (with Cambodians) and then betray my friends and colleagues. That's a heavy burden to bear no matter how many years roll by," says the retired U.S. Army colonel. "The downfall of the Khmer Republic not only resulted in the deaths of countless Cambodians, it has also crept into our souls."

Historians, distant from the passions of the actors, differ over Dean's efforts and American culpability.

Benedict Kiernan, a Yale University professor who has written extensively on Cambodia, says that given rifts within the Khmer Rouge leadership a political compromise earlier in the war might have been possible, resulting in a left-wing dominated coalition and not a fanatical revolution.

"Anything was worth trying to stop the Khmer Rouge before they got to Phnom Penh," says Heder, the academic, who reported in Cambodia during the war and was among those evacuated from the capital.

Milton Osborne, an Australian historian and diplomat who served in Cambodia, describes Dean's "controlled solution" as a "forlorn hope," with the Khmer Rouge determined to win totally and execute Phnom Penh's leaders. "By 1974, it was not a question of if, but when," he says.

Snepp believes that Dean, desperately grasping at straws, was "living in fantasy land."

Washington may have abandoned its ally, but the Cambodian elite also bears responsibility for its own demise. Snepp views President Lon Nol — corrupt, inept, superstitious and half-paralyzed — as one in a long line of similar leaders the United States would back in the following decades.

"What we have seen in all cases is that unless the U.S. has a politically viable domestic partner, neither limited nor massive military intervention is going to succeed," says Heder.

Timothy Carney, the embassy's political officer, drawing on his record as ambassador to several countries, says that "tolerating corruption saps the legitimacy and support for whatever authority we are trying to prop up in a country."

In the final days, Carney's task was to persuade, unsuccessfully, Cambodian leaders to flee the country.

The night before the evacuation, Dean and his deputy drank some of the ambassador's fine French wine so it wouldn't fall into Khmer Rouge hands. The next morning, sitting in his office for the last time, he read a letter from Prince Sirik Matak in which the respected former deputy prime minister declined evacuation and thus sealed his own death. It read: "I never believed for a moment that you have this sentiment of abandoning a people which has chosen liberty. I have only committed this mistake of believing in you the Americans."

Dean today describes it as the "greatest accusation ever made by foreigners. It is wrenching, no? And put yourself in the role of the American representative."

His embassy closed down at 9:45 a.m., the evacuees driven 10 blocks to a soccer field shielded by a row of apartment buildings from Khmer Rouge gunners about a mile away. The Sikorsky "Jolly Green Giant" helicopters were setting down. The Marines fanned out to form a security cordon around the landing zone.

But fears of possible reprisals by Cambodians proved unfounded.

Children and mothers scrambled over fences to watch. They cheered, clapped and waved to the 360 beefy, armed Marines. A Cambodian military policeman saluted Armstrong smartly. Disgusted and ashamed, he dropped his helmet and rifle, leaving them behind.

I tried to avoid looking into faces of the crowd. Always with me will be the children's little hands aflutter and their singsong "OK, Bye-bye, bye-bye."

By 12:15 the last helicopters landed on the deck of the USS Okinawa waiting off the Cambodian coast. Tactically, the 2 1/2-hour operation had been flawless.

In Phnom Penh, Douglas Sapper, an ex-Green Beret who stayed behind to save his company's employees, recalled the reaction of Cambodians who realized what had happened: "It was like telling a kid that Santa Claus was dead."

Five days later we received a cable from Mean Leang, an ever-jovial, baby-faced AP reporter who had refused to seek safety. Instead he wrote about the brutal entry of the Khmer Rouge into the city, its surrender and gunpoint evacuation. "I alone in office, losing contact with our guys. I feel rather trembling," he messaged. "Do not know how to file our stories now ... maybe last cable today and forever."

Barry Broman, then a young diplomat, remembers a Cambodian woman who worked upcountry monitoring the war for the embassy who had also refused evacuation.

"One day she said, 'They are in the city,' and her contact said 'OK, time to go.' She refused. Later she reported, 'They are in the building,' and again refused to leave her post. Her last transmission was, 'They are in the room. Good-bye.' The line went dead."