Although Mr. Khalifa played down his contributions to the Islamic State in the interview, prosecutors and the F.B.I. made clear he was a “prominent figure” within the Islamic State media unit, which he joined in April 2014. An F.B.I. agent described him as “essential” because of his fluency in Arabic and English and said he was in charge of the Islamic State’s “English Media Section,” according to the criminal complaint.
Prosecutors said that he assisted in the translation and narration of approximately 15 videos that were created and distributed by the Islamic State. Two of the most “influential and exceedingly violent” propaganda videos, prosecutors said, were called “Flames of War: Fighting Has Just Begun” and “Flames of War II: Until the Final Hour.” The first was distributed in September 2014 and the second in November 2017.
According to court documents, Mr. Khalifa was not just a propagandist but engaged in fighting. In the days before his capture by the Syrian Democratic Forces, he threw “grenades against opposing combatants,” prosecutors said.
F.B.I. agents interviewed Mr. Khalifa in March 2019, just months after he was captured. He said he was motivated to travel to Syria after watching videos of the Syrian government and listening to lectures of Anwar al-Awlaki, Al Qaeda’s leading voice in English, who was killed years earlier in a drone strike.
In an August 2013 email the F.B.I. obtained, Mr. Khalifa disclosed to a close relative that he had gone to Syria, and not Egypt as the relative had been led to believe, to fight. “I came here to join the mujahideen fighting against Bashar and the Syrian army,” he wrote.
The F.B.I. said that Mr. Khalifa flew to Turkey and then used a smuggler to enter Syria. He joined a battalion led by Omar al-Shishani, a Georgian militant. He received military training and participated in fighting against Syrian government forces in the Aleppo countryside. In about November 2013, he joined the Islamic State, swearing allegiance to its leader, Abu Bakr al-Baghdadi. While a member of the Islamic State, he was known as “Abu Ridwan al-Kanadi” and “Abu Muthanna al-Muhajir.,“ the F.B.I. said.
Mr. Khalifa thought he would be sent to an Islamic State training camp but instead he was recruited to join the media unit. The F.B.I. said Mr. Khalifa’s recruitment into the media unit would mark an almost five-year period in which he would become “a leading figure in ISIS’s English-language propaganda creation and distribution operations.”