Military science fiction is a subgenre of science fiction and military fiction that depicts the use of science fiction technology, including spaceships and weapons, for military purposes and usually principal characters who are members of a military organization, usually during a war; occurring sometimes in outer space or on a different planet or planets. It exists in a range of media, including literature, comics, film, television and video games. A detailed description of the conflict, belligerents (which may involve extraterrestrials), tactics and weapons used for it, and the role of a military service and the individual members of that military organization form the basis for a typical work of military science fiction. The stories often use features of actual past or current Earth conflicts, with countries being replaced by planets or galaxies with similar characteristics, battleships replaced by space battleships, small arms and artillery replaced by lasers, soldiers replaced by space marines, and certain events changed so the author can extrapolate what might have occurred. Source: Wikipedia (en)