According to the Wall Street Journal, Major Brandon Tyner is an American officer who was arrested in Britain on suspicion of spying for Russia. He was stationed in the UK as part of NATO's Rapid Reaction Force, a unit designed to command the alliance's ground forces in the event of a military conflict or crisis.
According to the publication, he was arrested during an undercover operation while talking to the British authorities, not knowing who he was talking to. He is on trial in both the UK and the US.