John Gunther Dean, U.S. ambassador to Cambodia, carries the closed embassy’s American flag in 1975 after evacuating from Phnom Penh and landing at a military base in Thailand. (Sal Veder/AP)

John Gunther Dean, a Jewish refu­gee from Nazi Germany who went on to serve as U.S. ambassador to five countries — including Cambodia, where he was forced to flee the American embassy days before it fell to the Khmer Rouge, and Lebanon, where he survived at least two assassination attempts — died June 6 at his home in Paris. He was 93.

His family confirmed the death and said the cause was decompensation.

In a Foreign Service career that spanned three decades and four continents, Mr. Dean embedded with troops in Vietnam, helped thwart a coup in Laos and held top diplomatic postings from 1974 to 1988, serving as ambassador to Cambodia, Denmark, Lebanon, Thailand and India.

Raised in Germany, where he learned English from a British governess and French from a tutor, he immigrated to the United States at 12 and served in the Army during World War II, wheedling information out of Nazi scientists while stationed at a secret interrogation camp in Northern Virginia.

His language skills proved a boon for the State Department, where he helped find a home for refugees in the aftermath of the Vietnam War and acquired a reputation as a skillful negotiator, notably while serving as ambassador to Lebanon from 1978 to 1981, during that country’s civil war.

Amid Cold War tensions, he reportedly sought to develop a dialogue with his Soviet counterpart in Beirut and met secretly with the Palestine Liberation Organization, helping negotiate the release of 13 hostages taken by Iranian students at the U.S. Embassy in Tehran. He also escaped rocket, machine gun and sniper attacks on his car.

Mr. Dean in 2015. (Jacques Brinon/AP)

But Mr. Dean was best known for his work in Southeast Asia, where he sought to navigate a tangle of conflicts between communist rebels, renegade military officers and established monarchies.

As deputy chief of mission in Laos, he forged a compromise agreement with the communist-led group Pathet Lao to avoid bloodshed and stifled an attempted coup in 1973, when a dissident Air Force general, Thao Ma, sought to overthrow the U.S.-backed government of Prince Souvanna Phouma.

Backed by officers who had taken refuge in northern Thailand, Thao Ma seized the airport in the capital, Vientiane, and announced his plot on state radio. Mr. Dean placed the prince in a safe house and was driven to the airport, where he parked in the middle of the runway. Wielding a bullhorn, he ordered the plotters to “go back across the Mekong” unless they wanted the Laotian military to lose American aid.

“Well, Gen. Thao Ma was not going to be put off by this show of bravado by a young civilian officer,” Mr. Dean said in a 2000 oral history. “He fired up his plane, and he tried to take off. Since I was about midway on the airstrip, he tried to avoid the car. He did not have enough height. In the process of avoiding a collision with my car, he veered off to the right and crashed. He was killed instantly.”

(Contemporary news reports differed on the precise cause of the general’s death, saying he died in a plane crash after being shot down over the city or was executed after being removed from the plane.)

Mr. Dean faced more turbulence in Cambodia, where he arrived in Phnom Penh as U.S. ambassador in 1974, with President Lon Nol’s forces losing ground against the Khmer Rouge, a group of brutal communist insurgents. Battling with Secretary of State Henry Kissinger, Mr. Dean called for a diplomatic effort to return the country’s exiled king, Norodom Sihanouk, and institute a coalition government.

But Mr. Dean received little support, as U.S. officials shifted resources away from Southeast Asia in the waning years of the Vietnam War. As the Khmer Rouge closed in, lighting up the night sky above Phnom Penh with explosions, flares and tracer bullets, he and his remaining staff were forced to evacuate on April 12, 1975, in a departure dubbed Operation Eagle Pull.

Mr. Dean later described the episode as the worst day of his life, linking the American withdrawal to the deaths of some 1.7 million Cambodians under Khmer Rouge leader Pol Pot, who was ousted after the Vietnamese invaded in 1979. “Now you must understand,” he told the Associated Press in 2015, “I was born in Germany and suffered under Nazi oppression, so how could I turn over a people to the butcher?”

According to the AP account, Mr. Dean and his staff left the embassy around 9:45 a.m. They were driven 10 blocks to a soccer field, where Marines ferried nearly 300 Americans, Cambodians and third-country nationals by helicopter to an aircraft carrier waiting off the coast. (Three weeks later, a more frenetic withdrawal took place in Saigon, marking the end of the Vietnam War.)

Mr. Dean was the last to board the final helicopter. A photograph that ran on the cover of Newsweek showed him arriving at a military base in Thailand with the embassy flag, the last vestige of American power in Cambodia, wrapped in a clear plastic sheet and clutched under his arm.

He later served with UNESCO as a special envoy to Cambodia, helping to reestablish international ties with the country as it ushered in democratic reforms in the early 1990s. But he said the George H.W. Bush administration declined his request to return the old embassy flag to Phnom Penh, in what he hoped would be an act of reconciliation.

“Why I took the flag down was my Boy Scout way of protecting it from desecration,” Mr. Dean told the New York Times in 1991. At the time of his death, the flag was still packed with his belongings.

He was born Gunther Dienstfertig in Breslau, Germany, (now the Polish city of Wroclaw), on Feb. 24, 1926. His father was a lawyer, and his mother was a homemaker who convinced the family to flee the country in late 1938, insisting that the Nazi persecution of Jews would not “blow over.”

Settling in Kansas City, they changed their family name to Dean, and Gunther adopted an “American” first name, John. He graduated from high school at 16, then studied government and international law and relations at Harvard before enlisting in the Army.

In part because of his fluency in German, he was sent to an interrogation camp known as P.O. Box 1142. “I would do sports with them in order to make them more cooperative,” he told NPR. “I would take some of the people out for dinner at a restaurant in town in civilian clothes.”

He graduated from Harvard in 1947, studied law at the Sorbonne in Paris and returned to Harvard to receive a master’s degree in international relations in 1950.

Later that year, he joined the Economic Cooperation Administration, which carried out the postwar economic aid package to Europe known as the Marshall Plan. Mr. Dean went on to open American missions in Mali and Togo, where he was stationed when the West African nation became independent in 1960, and in the early 1970s was detailed to the 24th Corps in the northern section of South Vietnam.

As deputy for CORDS (Civil Operations and Revolutionary Development Support), a civilian-military pacification program, he used a helicopter to rescue American advisers surrounded by North Vietnamese forces before being shot down near Quang Tri City. “Our helicopter dropped to the ground like a bag of potatoes,” Mr. Dean said in the oral history, adding that he was soon rescued, along with the remaining 50 besieged Americans.

Mr. Dean generated controversy toward the end of his career when he accused Mossad, the Israeli intelligence agency, of trying to assassinate him in Lebanon, in retaliation for his perceived support for the PLO. He also suggested that Israel was involved in the 1988 plane crash that killed Pakistan’s president, Gen. Mohammed Zia ul-Haq.

In a 2009 memoir, “Danger Zones,” Mr. Dean said his suspicions about the crash led the State Department to force him into retirement.

Survivors include his French-born wife of 66 years, Martine Dean, the former Marthe Duphenieux, of Paris and Verbier, Switzerland; three children, Catherine Curtis of Cajarc, France, Paul Dean of Geneva and Joseph Dean of Sebastopol, Calif.; and seven grandchildren.

Mr. Dean said he was long haunted by the United States’ legacy in Cambodia. Soon after leaving the country as ambassador, he received a letter signed by President Gerald R. Ford, who said that Mr. Dean was “given one of the most difficult assignments in the history of the Foreign Service and carried it out with distinction.”

And yet, Mr. Dean told the AP, he couldn’t help but believe he had “failed,” leaving behind friends, journalists and other Cambodian contacts who were executed and buried in Pol Pot’s infamous “killing fields.”

“I tried so hard,” he said. “I took as many people as I could, hundreds of them, I took them out, but I couldn’t take the whole nation out.”

Correction: An earlier version of this obituary incorrectly referred to the end of Mr. Dean’s diplomatic career. He said he was forced to retire after raising suspicions about the 1988 plane crash that killed Pakistan’s president, Gen. Mohammed Zia ul-Haq, but not after suggesting that Israel was behind an assassination attempt against him in Lebanon. The story has been updated.