Three short years ago, the rosier thinking in Washington was that Syrian President Bashar al-Assad, a British-trained eye doctor, had the dispositions of a Mideast peacemaker.

"Syria is an essential player in bringing peace and stability to the region," intoned then senator John Kerry, chair of the U.S. Senate's foreign relations committee, in Damascus in 2010 following one of his half-dozen parleys with Assad.

Kerry had been holding meetings with the dictator as early as 2006, even as Syria was (and still is) on the U.S. list of state sponsors of terrorism. 

How times have changed. With Syria now embroiled in a brutal civil war, two weeks ago Kerry, as U.S. secretary of state, likened Assad to some of history's most heinous despots, citing mounting evidence that his army used chemical weapons against rebels.

"Bashar al-Assad now joins a list of Adolf Hitler and Saddam Hussein who have used these weapons in time of war," Kerry said in a TV interview.

It's certainly not the first time American officials have tried to cozy up to an unsavoury strongman, only to turn on them when the tide changed. Over the last decades, a roster of the globe's tyrants have, at times, enjoyed the U.S.'s favour, or at the very least stood shoulder to shoulder with American leaders.

Here is a sampling of some of the more prominent cases:

Saddam Hussein, Iraq

The Iraqi leader certainly wasn't a pal of the United States when his armed forces invaded Iran in 1980. Iraq was on the U.S. list of state sponsors of terrorism and hadn't had normal diplomatic relations since 1967.

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Donald Rumsfeld, left, and Iraqi President Saddam Hussein shake hands in December 1983 in Baghdad. Rumsfeld met with Hussein during the war between Iran and Iraq as an envoy for U.S. President Ronald Reagan. (AFP/Getty)

But the U.S. also hoped to contain the Islamic Revolution in Iran and to counter the Soviet Union's attempts to influence the region. President Ronald Reagan sent Donald Rumsfeld, a former and future defence secretary, as special envoy to meet Hussein in 1983 and again in 1984.

The Reagan administration took Iraq off its terrorism list and in 1984 restored diplomatic relations. Secretly, military aid flowed to Hussein: cluster bombs through a CIA front company, as well as weapons components and intelligence about Iranian troops, a 2002 Washington Post exposé revealed. The Reagan and George H.W. Bush administrations authorized sales of anthrax and bubonic plague to Baghdad, even as intelligence reports were highlighting Iraq's "almost daily" chemical weapons use in the hostilities, the Post reported.  

By the end of the Iran-Iraq war, in 1988, government leaders had officially soured on Iraq again, trying to pass economic sanctions after it turned its guns — and gas — against its own Kurdish population. And then in 1991, after Iraq invaded Kuwait and American warplanes began dropping bombs over Baghdad, Hussein was officially the pariah he would remain until his final days. 

Hosni Mubarak, Egypt

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U.S. President Barack Obama greets Egyptian President Hosni Mubarak in Cairo in 2009. Two years later, Obama would call for Mubarak to 'immediately' democratize his country. (Amr Nabil/Associated Press)

During Mubarak's rule, from 1981 until protests swept him from office two years ago, he was an important American client in the Middle East. Egypt signed a peace treaty with Israel in 1978, and thereafter began to receive billions of dollars in U.S. military aid, second only to Israel every year from 1981 to 2002. Democracy was broached in talks with the dictator, but the lack of free and fair elections never saw him blacklisted.

The Obama administration at first stuck to its partner as the Arab Spring spread across the region in late 2010 and early 2011. On the second day of mass protests in Cairo, White House spokesman Robert Gibbs said, "We have a close and important ally in Egypt and they will continue to be." Then secretary of state Hillary Clinton said Mubarak was "looking for ways to respond to the legitimate needs and interests of the Egyptian people."

But within two weeks, the tone had changed. "The Egyptian government must put forward a credible, concrete and unequivocal path toward genuine democracy," Obama said. "We believe that this transition must immediately demonstrate irreversible political change."

Mubarak resigned the next day.

Moammar Gadhafi, Libya

The flamboyant "brother leader," as he styled himself, spent two decades dogging the West as a terrorist-funding rogue, starting after he organized the bloodless overthrow of Libya's King Idris in 1969. The U.S. placed his regime on its list of state sponsors of terrorism, as Gadhafi supplied arms, training, funds and haven to militant groups including the Irish Republican Army, the Basque ETA and the Black September Movement, which was responsible for the 1972 Munich Olympics attacks.

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Obama shakes hands with Moammar Gadhafi in Italy in 2009. After initially calling the 2011 Libyan uprising an internal struggle, the U.S. joined the military alliance that helped rebels overthrow the Libyan leader. (Alessandro Bianchi/Reuters)

Then, with characteristic caprice, Gadhafi in his latter years sought rapprochement with the very world powers he had devoted so many years to bedevilling. He agreed to compensate victims of Libyan-sponsored terrorism, including the 1988 bombing of Pan Am Flight 103, and allowed UN investigators into his country to examine and dismantle weapons of mass destruction.

The U.S. removed Libya from its terrorism blacklist in 2006, and world leaders such as British Prime Minister Tony Blair and Canadian Prime Minister Paul Martin paid him visits in his desert tent. Obama shook Gadhafi's hand at a G8 summit in Italy in 2009.

When the Arab Spring spread to Libya and Gadhafi turned his warplanes against his own people, the U.S. initially remained aloof. "This [is] ultimately and fundamentally an issue between the Libyan government, its leader and the Libyan people," a State Department spokesperson said in February 2011.

But the next month, the UN Security Council passed a resolution authorizing military force against Libya, and the U.S. dispatched warships, bombers and fighter jets. "I think it is just a matter of time before Gadhafi goes," Obama said that June. "What you're seeing across the country is an inexorable trend."

Manuel Noriega, Panama

Manuel Noriega took U.S. military training and was on the CIA's payroll for years, as he helped the United States spy on other Latin American countries and suppress the spread of socialism and communism.

By the time George H.W. Bush became CIA director in 1976, the agency knew that its collaborator was said to be involved in high-level drug trafficking from his perch as head of Panama's military intelligence. Noriega's operatives had also bribed American soldiers to get at details about U.S. eavesdropping on Panama.

Despite Noriega's shady reputation and published reports that some of his country's officials were laundering drug money, Bush, as vice-president, went to Panama to meet him in 1983, after the strongman had consolidated power as the country's de facto ruler. Photos show them lounging on couches.

Bush's ties to Noriega dogged him when he ran for the presidency in 1988. Official views of the Panamanian general had changed, with the U.S. Senate denouncing his "corruption and drug dealing" and his ties to Colombian drug lord Pablo Escobar's Medellin cartel. He was also indicted in Florida on narcotics and racketeering charges.

After the election, Bush channelled that animus into the eventual invasion of Panama in 1989. Noriega was captured and returned to the U.S., where was tried, convicted and sentenced to 40 years in 1992.

Fidel Castro, Cuba

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Cuban revolutionary leader Fidel Castro shakes hands with U.S. Vice-President Richard Nixon during a media reception in Washington in April 1959. (Keystone/Getty)

The guerrilla leader enjoyed a fleeting popularity among the U.S. public after he deposed dictator Fulgencio Batista and took over Cuba in 1959. On a visit to the United States in April of that year, cheering crowds, with some of their children dressed up like rebels, greeted Castro in the streets. "Fidel Castro swept through Houston in glory bordering on pandemonium, with sirens failing to drown out the cheers of his admirers," the Houston Chronicle reported.

It was hoped that Castro would bring democracy to Cuba. The revolutionary appeared on the TV interview show Meet the Press, and later joined Vice-President Richard Nixon in Washington. Nixon told him that "he had done extremely well" on TV, and "had fought so gallantly" against "dictatorship" in Cuba.

The aim was to steer him away from the radical rhetoric he had espoused during the revolution, and on that score Nixon's assessment showed concerns. "His ideas as to how to run a government or an economy are less developed than those of almost any world figure I have met in 50 countries," the vice-president wrote in a memo.

U.S. officials saw very quickly that it was not to be, and within a year, President Dwight Eisenhower authorized the CIA to plot Castro's overthrow.