Montgomery is the Enterprise security guard ordered to escort Commodore Matt Decker to sickbay in The Doomsday Machine, only to be overpowered by him in a corridor on the way.
Montgomery is a security officer aboard the USS Enterprise in the Original Series episode The Doomsday Machine. He is on the bridge when Spock, backed by Kirk's personal authority, finally relieves Commodore Matt Decker of the command he had seized.
Spock orders Montgomery to accompany Decker to sickbay for an examination by Doctor McCoy. Decker goes quietly at first, then fakes a coughing fit in the corridor and attacks his escort. After a hard hand-to-hand struggle the commodore knocks the guard out.
Montgomery's defeat leaves Decker free to reach the hangar deck, steal a shuttlecraft and fly it into the planet killer, a death that gives Kirk the idea of destroying the machine from the inside.