Marine

''This is about the marines that appear in Doom 3. For the marine that the player controls, see Doom's protagonist''

In Doom 3, the player may occasionally come across friendly marines. Marines are usually equipped with a Machine Gun but are fairly poor fighters in comparison to the player (for example, one can be killed by a lone zombie). Marines are never seen in combat during gameplay other than in multiplayer. However, during a cutscene several marines are seen being killed by a number of Wraith.

Trivia
There is a Doom 3 mod that enables to have marines on its side and help the player fight the Hellish forces.