It sounds like a fanciful script for a Hollywood thriller: foreign government agents plotting assassinations in the United States.

To be sure, there have been suspected state-sponsored killings in the past 20 years that have grabbed international headlines. Former Russian agent Alexander Litvinenko's poisoning with a radioactive isotope in London in 2006 is one example; the murder of journalist Jamal Khashoggi at a Saudi diplomatic facility in Istanbul in 2018 is another.

And just this month, Maksim Kuzminov, a Russian pilot who defected to Ukraine after Russia's full-scale invasion, was found shot dead in southern Spain. The Kremlin declined to comment on the case, but there are suspicions Kuzminov's killing could have been a Russian-ordered assassination.

None of those took place in the United States. But in the past few years, there have been assassination plots aplenty in the U.S. In just the past 18 months, the Justice Department says it has foiled four of them on American soil.

"We face a rising threat from authoritarian regimes who seek to reach beyond their own borders to commit acts of repression, including inside the United States," Matthew Olsen, the head of the Justice Department's National Security Division, said in 2022 when announcing charges in one of the cases.

In that prosecution, the government alleges that a member of Iran's Islamic Revolutionary Guard Corpsplotted to murder former U.S. national security adviser John Bolton.

"This is an especially appalling example of the government of Iran perpetrating egregious acts of transnational violence, in violation of U.S. laws, and our national sovereignty," Olsen said at the time.

The case echoes a 2012 prosecution the department brought accusing Iran of plotting to kill the Saudi ambassador to the U.S. in Washington, D.C.

Iran also has had a hand in two other recent assassination plots, according to court papers. One targeted an Iranian-American writer in New York, the other a couple in Maryland, one of whom was an Iranian defector.

But it's not just Iran.

American allies have also targeted assassinations on U.S. soil

Late last year, the Justice Department said it had foiled a plot directed by an Indian government official to kill a U.S. citizen in New York City. The intended victim was an activist for Sikh independence.

The U.S. announced charges in the case some two months after Canada's prime minister accused India of being behind the killing of a Sikh activist near Vancouver.

That alleged plot on U.S. soil sent shockwaves through Washington in large part because India is an American partner and fellow democracy.

It seems especially brazen for a U.S. ally to take such a step. But during the Cold War, some American allies did exactly that.

One of them was Chile's Gen. Augusto Pinochet. In 1976, Chilean intelligence operatives killed a former ambassador, Orlando Letelier, and his American colleague, Ronni Moffitt, in a car bombing in Washington, D.C.

"When a bomb goes off in a car in the rush hour on Sheridan Circle, on Mass Ave., in the middle of Embassy Row and shatters the windows for a block around, that's a big deal in Washington," said Michael Glennon, a law professor at Tufts University.

At the time of the bombing, Glennon was an attorney working for the U.S. Senate. Letelier's killing, Glennon said, helped spark a Senate investigation that Glennon oversaw into the activities of friendly foreign intelligence agencies in the United States.

The investigation, he said, received lots of reports from foreigners in the U.S. who claimed to be under surveillance, or subject to harassment, or even targeted for assassination by foreign intelligence agencies.

But Glennon said that actual assassinations of U.S. residents were extremely rare.

"The Letelier assassination was an anomaly," he said. "These foreign intelligence agencies, including the Soviets, I might add, stopped at the line of assassination. That was verboten."

But some of the countries that did cross that line were allies of Washington.

Five years after the Letelier bombing, two union organizers in Seattle, Silme Domingo and Gene Viernes, were murdered at their local cannery workers union office. Both men were opponents of Philippines dictator Ferdinand Marcos and his wife, Imelda.

An American court later found the Marcoses liable for the murders. They were found to have been part of a conspiracy to infiltrate, monitor and neutralize anti-Marcos opposition in the U.S.

In 1984, a Chinese American, Henry Liu, was gunned down in the garage of his home in Daly City, Calif. U.S.-based members of a Taiwanese criminal gang, acting at the behest of Taiwan military intelligence official, were convicted of the murder.

While it may seem counterintuitive that an ally would do something on U.S. soil that America's main geopolitical adversary would not, but Glennon says he thinks part of the explanation boils down to resources.

"The FBI ran an extremely aggressive counterintelligence operation directed at the Soviet Union and communist bloc allies," he said. "These people were under a microscope, and we really knew everything they were doing. It was just amazing."

But the FBI, he said, couldn't devote the same sort of attention and resources to allies, as well.

"They didn't look as closely at some of the friendlies, so-called, and the friendlies knew that," Glennon said.

The recent run of cases brought by the Justice Department raises the question of whether state-sponsored assassinations are becoming more common.

Glennon cautions against drawing any firm conclusions, despite the recent prosecutions, because "these intelligence services are extremely adept at disguising what they do."

Why we're seeing more of these assassination attempts

Rory Cormac, a professor of international relations at the University of Nottingham in the U.K., agrees, but said that "it certainly feels like we are seeing more because they are brazen and because obviously the Americans are more willing to expose publicly this activity."

He points to a couple of factors that he says likely contribute to the apparent increase.

"I think the landscape is changing and the norms against this are eroding," Cormac said. "And that is seeing more actors feeling like they can get away with it."

He also points to new technology, particularly the spread of armed drones, which is just a modern means to conduct a targeted killing.

The United States has used drones for more than a decade to target suspected terrorists around the world. Washington justifies its actions as self-defense in response to an imminent threat.

Cormac says he sees a stark difference between murdering dissidents abroad and killings terrorism suspects in a drone strike.

But, he says, critics accuse the U.S. of hypocrisy, and point to the 2020 American strike that killed Iranian Gen. Qassem Soleimani in Iraq as a prime example.

"They'll see that as another nail in the coffin of taboos against assassinations and targeted killings," Cormac said.

The Justice Department has said that the Iranian plot targeting Bolton appeared to be in retaliation for Soleimani's death.

None of the recent plots in the U.S. has succeeded. But that doesn't mean foreign powers — allies or adversaries — won't keep trying.

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