Six years after the Islamic State beheaded American journalists and aid workers on camera, two men have been charged in U.S. federal court for involvement in those deaths.

The case against Alexanda Kotey and El Shafee Elsheikh in Alexandria, Va., is the first use of the U.S. justice system to seek to hold Islamic State fighters accountable for the murder of American citizens.

“Although we cannot bring them back, we can and will seek justice for them, their families, and for all Americans,” Attorney General William P. Barr said in a statement.

He and other law enforcement officials described the charges as a warning to both U.S. citizens who join terrorist groups and foreign fighters who harm Americans that they cannot escape prosecution.

Alexanda Kotey, part of a group of four British Islamic State militants dubbed the "Beatles," spoke to The Post in a detention center in Syria on Aug. 4, 2019. (The Washington Post)

“If you have American blood in your veins or American blood on your hands, you will face American justice,” said assistant attorney general for national security John Demers at a news conference Wednesday.

Elsheikh and Kotey were flown Wednesday to the United States from Iraq, where they had been held by the U.S. military for the past year.

The men made their first appearance in court Wednesday, where they were assigned attorneys and will be arraigned Friday. Appearing by video out of concern over the coronavirus, they appeared confused. “Under whose jurisdiction am I?” Elsheikh asked. “Does this mean I’m under arrest?”

El Shafee Elsheikh, who is accused of involvement in the Islamic State’s executions of Western hostages, spoke to The Post in Syria on Aug. 4, 2019. (The Washington Post)

Kotey was born in London; Elsheikh moved there from Sudan with his family as a child. Both became radicalized in Britain, and prosecutors noted they were arrested on Sept. 11, 2001, after taking part in a demonstration cheering the attacks on the World Trade Center and Pentagon.

In 2012, both traveled to Syria to join Islamist militant groups. By that fall, according to prosecutors, they were torturing hostages for the Islamic State. Prisoners say they were waterboarded, beaten, subjected to electric shocks and made to fight each other, among other torments.

In interviews with The Washington Post and other news outlets, Elsheikh and Kotey admitted joining the Islamic State and taking information from hostages for ransom negotiations. They said they engaged with Americans James Foley, Kayla Mueller, Steven Sotloff, Peter Kassig and other Western prisoners who were subsequently killed. But they claimed to have no involvement in or advance knowledge of those executions.

The indictment says they were directly involved in torture and killings. According to prosecutors, when another man, Mohammed Emwazi, executed a Syrian prisoner, Elsheikh videotaped the slaying in front of a group of European hostages while Kotey instructed them to kneel and hold handmade signs pleading for release. After bringing the group back to an Islamic State-run prison in Syria, according to prosecutors, Elsheikh told one hostage, “You’re next.”

The indictment also says the two worked closely with Abu Muhammad al-Adnani, a top strategist and chief spokesperson for the Islamic State until his death in 2016.

Emwazi, who wielded the knife in infamous Islamic State videos, was killed in a drone strike in 2015. Like Kotey and Elsheikh, Emwazi — better known as “Jihadi John” — was raised in West London. Together with a fourth Londoner, Aine Davis, the group became known by their captives as “the Beatles” because of their British accents.

Kotey and Elsheikh were captured in Syria by U.S.-backed Kurdish forces in 2018; Davis is imprisoned in Turkey. The U.S. military took custody of the two defendants from its Kurdish allies after Turkey invaded northern Syria.

The men will be prosecuted in federal court and are charged with hostage-taking resulting in death, conspiracy to murder U.S. citizens outside the United States, conspiracy to provide material support to a foreign terrorist organization and related conspiracy charges. If convicted of the most serious charges, they face mandatory life sentences.

U.S. Attorney G. Zachary Terwilliger calls the case “one of the most impactful, important cases we’ve had in this country.”

The defendants and their families fought for a prosecution in Britain rather than the United States, where criminal punishment is harsher. But Britain stripped Kotey and Elsheikh of their British citizenship and expressed reservations about a prosecution there. A court in London last month cleared the way for British authorities to provide evidence to U.S. law enforcement after Barr agreed not to seek the death penalty in exchange.

Demers said the British evidence allowed prosecutors to tell “the fullest story we could about what these defendants did.”

In a statement Wednesday by a foundation created in Foley’s honor, the families thanked British and U.S. authorities for their work. “James, Peter, Kayla and Steven were kidnapped, tortured, beaten, starved, and murdered by members of the Islamic State in Syria,” they said. “Now our families can pursue accountability for these crimes against our children in a U.S. court.”

The bodies of the slain hostages have never been found; the circumstances of Mueller’s death remain unclear. Their families said in an editorial this year that they hope a prosecution will reveal “the full truth” of what happened to their children.

Nicholas Lewin, a former federal prosecutor in Manhattan who successful tried a number of senior al-Qaeda figures, said the indictment reflects a playbook used successfully in the years after 9/11: identify overseas operatives, bring them to the United States and charge them with, among other things, conspiracy to kill Americans and material support. “This was the al-Qaeda prosecution game plan,” he said, “and now we’re using it against ISIS.”