Johannes Grant
Johannes Grant or Johannis Grandi was a mercenary employed by the Byzantine Empire at the fall of Constantinople in 1453. Contemporary Greek and Latin accounts referred to him as being German, although Runciman has suggested he may actually have been a Scot named John Grant. He appears to have been affiliated with the Genoese contingent of mercenaries at the siege, possibly part of the men commanded by Giovanni Giustiniani. His use of counter-mining tunnels prevented the Turks from weakening or invading Constantinople from under the walls.