Military science fiction
David Drake wrote stories about future mercenaries, including the Hammer's Slammers series (1979), which follows the career of a future mercenary tank regiment. Drake's series which "helped initiate a fashion for sf about mercenaries", including The Warrior's Apprentice (1986) by Lois McMaster Bujold.
A 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 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.
The Encyclopedia of Science Fiction lists three notable women authors of MSF: Lois McMaster Bujold; Elizabeth Moon (particularly her Familias Regnant stories such as Hunting Party (1993)), and Karen Traviss.

Political themes: Several 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 policymakers 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:

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.

Practical applications by military: In 1980 and 1981, two science fiction authors inspired President Ronald Reagan's vision for a Strategic Defense Initiative in which satellites would be set up to shoot at nuclear missiles. The two authors were Larry Niven, the author of the Ringworld series, and Jerry Pournelle. Along with like-minded colleagues, they formed a committee to lobby the United States on space issues and influence Reagan's space policies. Pournelle advocated a "robust, technocratic military state". In addition to Pournelle's science fiction writing, he wrote a "paper for the Air Force on stability's role in national security".
President Reagan read the space advice that Niven, Pournelle, and their colleagues prepared, which influenced Reagan's 1983 Strategic Defense Initiative. "Niven and Pournelle saw an opportunity to shape the great void in their political image, and Reagan viewed space as yet another tool to defend America against the communist superpower...". Science fiction authors such as Arthur C. Clarke and Isaac Asimov criticized the Strategic Defense Initiative.
After the 9/11 terrorism attacks, a group of sci-fi authors called Sigma, including Pournelle and Niven, advised the "Department of Homeland Security on technological strategies for defeating terrorist threats."
In 2021, Worldcrunch reported that the French military has hired fiction writers to develop futuristic warfare scenarios, including situations that the military cannot directly study for "ethical reasons, such as Autonomous Lethality Weapon Systems (ALWS), or augmented humans." The French military says the authors are asked to imagine warfare situations that "destabilize us, scare us, blame, or even beat us", in order to provide the army with a "fresh set of practice scenarios". Military planners use the science fiction authors' scenarios to "prepare for previously unthought of situations", "boos[t] creativity" and help the military become "more resourceful."
The German military is also using science fiction to help its military but in its approach, they do not hire science fiction writers to develop scenarios. Instead, they "use existing science fiction" to help the army "predict the "world's next potential conflict."
The UK Ministry of Defence (MOD) hired two science fiction writers to pen short stories about "what the wars of tomorrow will look like."
The MOD hired Peter Warren Singer and August Cole to write eight short stories about threats from "emerging technologies" including "artificial intelligence (AI), data modeling, drone swarms, quantum computing and human enhancement" in a battlefield context.
The MOD hired sci-fi writers because they have a "unique ability to imagine the unimaginable." As well, both authors know about "security subjects and modern warfare."
They advocate the use of "Fictional Intelligence" ("FicInt"), which they define as "useful fictions". FicInt, a concept developed by Cole in 2015, combines "fiction writing with intelligence to imagine future scenarios in ways grounded in reality."

See also: List of military science fiction works and authors
Space warfare in science fiction
Weapons in science fiction
War novel


== References ==