Military science fiction
Military science fiction is a subgenre of science fiction that features the use of science fiction technology, mainly weapons, for military purposes and usually principal characters that are members of a military organization involved in military activity, usually during a war; occurring sometimes in outer space or on a different planet or planets. It exists in literature, comics, film, and video games.
A detailed description of the conflict, the tactics and weapons used for it, and the role of a military service and the individual members of that military organization forms 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 of similar characteristics, battleships replaced by space battleships and certain events changed so that the author can extrapolate what might have occurred.
Traditional military values of bravery, sacrifice, sense of duty, and camaraderie are emphasized, and the action is usually described from the point of view of a soldier. Typically, the technology is more advanced than that of the present and described in detail. In some stories, however, technology is fairly static, and weapons that would be familiar to present-day soldiers are used, but other aspects of society have changed. For example, women may be accepted as equal partners for combat roles. In many military science fiction stories, technological advances are often basic to plot developments. Some works draw heavy parallels to human history and the fact that scientific breakthroughs or new doctrine can severely change the outcome of battles and the way war is fought. Many works explore how progress or changes to the aforementioned affect military doctrine and also how the protagonists and antagonists reflect on and adapt to these changes. Military science fiction is also part of the "military and popular culture" subject field. 
Several subsets of military science fiction overlap with space opera, concentrating on large-scale space battles with futuristic weapons. At one extreme, the genre is used to speculate about future wars involving space travel, or the effects of such a war on humans; at the other, it consists of the use of military fiction plots with some superficial science fiction trappings. The term "military space opera" is occasionally used to denote this subgenre, as used for example by critic Sylvia Kelso when describing Lois McMaster Bujold's Vorkosigan Saga. Another example of military space opera would be the Battlestar Galactica franchise and Robert A. Heinlein's 1959 novel Starship Troopers.
The key distinction of military science fiction from space opera is that the principal characters in a space opera are not military personnel, but civilians or paramilitary. Military science fiction also does not necessarily always include an outer space or multi-planetary setting like space opera.
Precursors for military science fiction can be found in "future war" stories dating back at least to George Chesney's story "The Battle of Dorking" (1871). Other works of fiction followed, including H.G. Wells's "The Land Ironclads". Eventually, as science fiction became an established and separate genre, military science fiction established itself as a subgenre. One such work is H. Beam Piper's Uller Uprising (1952) (based on the events of the Sepoy Mutiny). Robert A. Heinlein's Starship Troopers (1959) is another work of military SF, along with Gordon Dickson's Dorsai (1960), and these are thought to be mostly responsible for popularizing this subgenre's popularity among young readers of the time.
The Vietnam War resulted in veterans with combat experience deciding to write science fiction, including Joe Haldeman and David Drake. Throughout the 1970s, works such as Haldeman's The Forever War and Drake's Hammer's Slammers helped increase the popularity of the genre. Short stories also were popular, collected in books like Combat SF, edited by Gordon R. Dickson. This anthology includes one of the first Hammer's Slammers stories as well as one of the BOLO stories by Keith Laumer and one of the Berserker stories by Fred Saberhagen. This anthology seems to have been the first time SF-stories specifically dealing with war as a subject were collected and marketed as such. The series of anthologies with the group title There Will be War edited by Pournelle and John F. Carr (nine volumes from 1983 through 1990) helped keep the category active, and encouraged new writers to add to it.
A special twist was introduced in Harry Turtledove's Worldwar series depicting an alternate history in which WWII is disrupted by extraterrestrials invading Earth in 1942, forcing humans to stop fighting each other and unite against this common enemy. Turtledove depicts the tactics and strategy of this new course of the war in great detail, showing how American, British, Soviet and German soldiers and Jewish guerrillas (some of them historical figures) deal with this extraordinary new situation, as well as providing a not unsympathetic detailed point of view of individual invader warriors. In the war situation posited by Turtledove, the invaders have superior arms, but the gap is not too wide for the humans to bridge. For example, the invaders have more advanced tanks, but the German Wehrmacht's tank crews facing them - a major theme in the series - are more skilled and far more experienced.
A number of authors have presented stories with political messages of varying types as major or minor themes of their works.
David Drake has often written of the horrors and futility of war. He has said, in the afterwords of several of his Hammer's Slammers books (1979 and later), that one of his reasons for writing is to educate those people who have not experienced war, but who might have to make the decision to start or endorse a war (as policy makers or as voters) about what war is really like, and what the powers and limits of the military as an instrument of policy are.
David Weber has said that:
For me, military science-fiction is science-fiction which is written about a military situation with a fundamental understanding of how military lifestyles and characters differ from civilian lifestyles and characters. It is science-fiction which attempts to realistically portray the military within a science-fiction context. It is not 'bug shoots'. It is about human beings, and members of other species, caught up in warfare and carnage. It isn't an excuse for simplistic solutions to problems.
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- Ender M.G., Reed B.J., Absalon J.P. (2020) Popular Culture and the Military. In: Sookermany A. (eds) Handbook of Military Sciences. Springer, Cham. https://doi.org/10.1007/978-3-030-02866-4_36-1 https://link.springer.com/referenceworkentry/10.1007/978-3-030-02866-4_36-1
- David G. Hartwell, Kathryn Cramer, The Space Opera Renaissance, Tor Books, ISBN 0-7653-0617-4. Introduction, p. 251
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