warfare is a staple of science fiction, where it is shown with a wide range of realism and plausibility. Fictional space warfare includes anticipated future technology and tactics, and fantasy- or history-based scenarios in a scifi setting. Some portray a space military as like an air force; others depict a more naval framework. Still others suggest forces more like space marine: highly mobile forces doing interplanetary and interstellar war but most of the conflict happens in terrestrial environments. The main sub-genres of the science fictional space warfare thematic genre are space opera, Military and Space Western. Though sword and planet stories like Finisterre universe by C. J. Cherryh might be considered, they rarely feature such technologies. These three genres often intertwine and have themes that are common to all. Written Space Westerns are often based directly on existing established scifi space opera franchises with expanded universes like Star Wars and Star Trek, including Warhammer 40,000: the most popular space opera military miniature wargame which spawned successful spin-off media: novels, video-games and on-going live adaption based on books by Dan Abnett. Both kinetic and directed energy weapons are often seen, along with various military space vessels. E. E. Smith's Lensman is an early example, which also inspired the term space opera due to the grandiose scale of the stories. Orson Scott Card's Ender's Game series is a notable example in that it makes a conjecture as to what sort of tactics and training would be needed for war in outer space. Other scifi authors have also delved into the tactics of space combat, such as David Weber in his Honorverse series, and Larry Niven and Jerry Pournelle in their Mote in God's Eye series. A more recent example is Alastair Reynolds' Revelation Space universe, which explores combat at relativistic speed. Robert A. Heinlein's Starship Troopers is perhaps one of the best-known and earliest explorations of the "space marine" idea. Space-based vehicular combat is portrayed in many movies and video games, most notably Star Wars, "Stargate", Halo, Descent, Gundam, Macross, Babylon 5, and Star Trek. Games such as the Homeworld series have interesting concepts for space warfare, such as 3D battle formations, plasma-based projectors that get their energy from a ship's propulsion system, and automated uncrewed space combat vehicles. Other series, such as Gundam, prominently show vehicular combat in and among many near future concepts, such as O'Neill cylinders. Fictional galaxies with