The Metropolitan Police said the arrest was made on suspicion of violating two sections of the Act—assisting a foreign intelligence service and obtaining or disclosing protected information. Searches are underway at two locations in Gloucestershire. The suspect remains in custody at a London police station.

The soldier was based at Imjin barracks in Innsworth, which serves as the headquarters for NATO’s Allied Rapid Reaction Corps. U.S. Army Counterintelligence Command described the individual as a “senior soldier” and said the alleged conduct was a “sobering reminder that insider threats are real and persistent.” Brig Gen Sean Stinchon, the commanding general of the command, encouraged anyone with suspicious information to report it to local counterintelligence offices.

FBI Director Kash Patel called the arrest “important” and emphasized the seriousness of the allegations. “This FBI has no tolerance for anyone who breaks their oath to the United States and whose actions endanger our national security and that of our partners,” Patel said. He noted that the FBI has made 167 counterintelligence and espionage arrests over the past 21 months, a 53% increase.

Deputy Assistant Commissioner Vicki Evans, the UK’s senior national coordinator for counterterrorism policing, called the investigation a “significant arrest and investigation.” She praised the strength of U.S.-UK security partnerships and said the allegations are serious and the investigation is ongoing.

Police confirmed the arrest was not connected to other counterterrorism investigations, including a suspected plot linked to Iran in September at RAF Fairford, a U.S.-run base near Gloucester. The U.S. Air Force had previously withdrawn bombers from the base following a perceived threat.

The Metropolitan Police said its counterterrorism units worked closely with MI5, the U.S. Army Counterintelligence Command, and the FBI. Officials from both countries praised the collaboration as essential to protecting national security.