In Biggles Follows On, Johnny Briggs was an American serviceman who deserted to work in the propaganda base at Kratsen. He was a friend of another American soldier, Joe Clutson and both of them were apparently enticed into deserting by someone known as "the Sergeant", a brutal man, apparently a renegade British soldier, who was put in charge of the other deserters. The sergeant had apparently murdered a girl while he was in Berlin as part of the occupation force there. Presumably he had met Briggs and Clutson in Berlin as well. Johnny Briggs had apparently told the Sergeant to his face that he was "a dirty, lying, sneaking rat" and as a result, the sergeant had hit him on the head with a hammer and killed him. Later Joe Clutson would shoot the sergeant in revenge.
Briggs never appeared in the story in person as by the time Biggles arrived in Kratsen, he had already been murdered.