Military science fiction has often explored the ethical and cultural effects of war in the future. Here's a guide to some notable entries in the field that do the best job depicting realistic warfare.
Starship Troopers, Robert Heinlein
When one thinks of military science fiction, Robert Heinlein's classic novel Starship Troopers is often the first to come to mind. It paved the way for a lot of military science fiction, but it did that by going beyond the battlefield - this story extends military culture from the lives of the soldiers, to the root causes of the story's conflict. Heinlein even explores how the culture became militant in the first place.
We follow Juan Rico, a member of the Mobile Infantry, a powered-armor infantry unit that is deployed in the war against an insect based species known as the Bugs, watching him emerge from training to engage in battlefield combat. The story alternates between Rico's military life and flashbacks to his life beforehand and the training that he underwent, all the while serving to explore several political theories of civic responsibility and military ethics.
Cobra Trilogy, Timothy Zahn
Timothy Zahn is known far more for his Star Wars novels, but he has written extensively in the science fiction realm, especially in military SF. Some of his best books have included the Conqueror's Trilogy and Blackcollar, but what springs to mind first is his Cobra series. These books follow a group of soldiers known as Cobras, who have been augmented to pack a greater punch on the battlefield. Rather than exploring the battlefield abilities of these soldiers, Zahn looks to their lives after the war and how they adapt, as the modifications that they receive are permanent.
Ender's Game, Orson Scott Card
Ender's Game is another of the prominent works of military SF. It follows Andrew 'Ender' Wiggen as humanity is fighting a far off and seemingly unstoppable insectoid race. Andrew and other children are selected for an orbital school that is designed to turn them into the leaders who will lead Earth to victory. Unlike other books, which focus on combat, Ender's Game largely focuses on the command and strategy level of warfare, as Ender proves to be a brilliant subject, and eventually takes command of Earth's forces as they travel closer to the enemy's home planet.
The Forever War, Joe Haldeman
Joe Haldeman's 1974 novel The Forever War explores both combat and culture. Earth is engaged in an interstellar war, and the story's hero, William Mandella, is recruited to fight far from home. After a period of training, they travel to the battlefield at faster-than-light-speeds. But this subjects the soldiers to relativity: They arrive to find themselves outgunned on the battlefield, and return to find a very different Earth than when they left. Where Starship Troopers is considered to be fairly pro-military, The Forever War was written in the aftermath of Vietnam (Haldeman was a veteran) and is largely seen as an anti-war novel.
Old Man's War, John Scalzi
Published in 2005, John Scalzi's novel Old Man's War was nominated for a Hugo Award and Scalzi followed up with two sequels. The story follows John Perry, a seventy-five-year-old who enlists in the Colonial Defense Forces, and begins a military career that leaves him an experienced soldier and leader. But over the course of the carnage, he is left to wonder whether the bloodshed is really worth it. The book has been compared to both The Forever War and Starship Troopers.
Broken Angels, Richard K. Morgan
Broken Angels is the second book in the trio of Takeshi Kovacs novels penned by UK author Richard K. Morgan. Unlike the first book of the three, which had more of a detective-noir feel, we are now thrust into the military background of Morgan's starring character, Takeshi Kovacs. Kovacs is serving with a mercenary unit when he is contracted to help protect an expedition that has uncovered a Martian artifact located in the middle of a war zone. Morgan applies his own twists to the genre. Unlike other military science fiction books, Morgan doesn't look at the themes of warfare, but instead at mercenary and corporate military units, as well as the individual conduct of the soldiers.
Armor, John Steakley
Armor has been compared to Robert Heinlein's Starship Troopers. The title refers to the powered armor that the soldiers in the story use (to fight insectoid aliens), but also refers to the psychological effects of war. The story's hero, Felix, is put into battle again and again, surviving against incredible odds, but finds that these battles take an incredible toll.
Wess'Har Wars, Karen Traviss
Karen Traviss's Wess'Har series spans six books (City of Pearl, Crossing the Line, The World Before, Matriarch, Ally and Judge) and begins in the near future, before jumping ahead several hundred years. Traviss' protagonist, Shan Franklin, is a police officer who is sent to the world Cavanagh's Star, to recover a colony that had been sent there. There, accompanied by a unit of Royal Marines, they meet several new alien races, and become embroiled in a massive conflict that humanity is dragged into as well.
This series works well because of Traviss' restraint. While these books feature combat, they are mainly political and ethical in nature, dealing with genocide and the limits of warfare. Particularly interesting is that Traviss' books don't necessarily take the side of humanity; she explores a number of other races and their motivations for going to war.
Vatta's War Cycle, Elizabeth Moon
Vatta's War is a series of five books by Elizabeth Moon that follow Kylara Vatta after she is drummed out of a military academy and thrust into the family business of transporting goods. But there is combat: she fights battles with pirates and mercenaries, while working to defend her family and livelihood. Over the course of the series, threats mount and Ky is forced to take command of a task force to defend against a massive pirate armada.
Probability Moon, Nancy Kress
Probability Moon is the first book a trilogy where Earth is (surprise!) fighting against an alien race that has them outmatched. This book deals with the discovery of an alien artifact that can help turn the tide of the war in humanity's favor. What is interesting about these books is that they follow a select number of characters outside of the military who have to interact with a society that is increasingly under the control of military forces. Kress also deals with military tactics that conform to physics, which is a nice change in general.
X-Wing Series, Michael A. Stackpole / Aaron Allston
I wasn't going to approach any elements of the Star Wars franchise, but I couldn't really justify leaving off Michael A. Stackpole and Aaron Allston's 9 book X-Wing series, which deals largely with space battles. This series stands out, because it gives us a strong sense of military culture, jargon and environment as we get to know the Rogue and Wraith Squadrons.
My first memory of Battlestar Galactica is an image of Adama in uniform in a copy of SciFi Magazine. I remember thinking that it was interesting that a SciFi show had such a realistic-looking uniform, and it only got better from there. It also doesn't hurt that the show's CGI is run by Zoic, which makes the space battles something to die for.
Battlestar Galactica has been known for bucking trends when it came to television SF, and it did so in spectacular fashion over four seasons. Soldiers looked like soldiers, with their simple helmets, knee pads, and guns. But beyond the look of the military, Galactica gave us a stunning array of realistic military tactics.
Stargate SG-1 largely uses the modern day US military, and did so with a growing understanding over the course of the show's ten year life. The first couple of seasons took a number of liberties throughout, but over the course of the show, its fictional military evolved as the real-life US military evolves (such as new weapons and uniforms). We also got a fair amount of space battles between the human SG forces and the Goa'Uld forces.
Babylon 5 introduces a sort of UN level of politics to combat-oriented science fiction. The show follows a five year arc that includes massive conflicts between races, culminating in rebellion and a showdown of good and evil. This show certainly wanders into the morally gray area and as such, shows the complexity and multiple-faceted nature of war. The overall look and feel of the show evolves over time, and the military element certainly improves as well.
The popular sequel to the film Alien, this film features a unit of Colonial Marines that accompany Ripley upon her return to the planet LV-426. This was a big change from the original film, which was more of a horror film. After contact is lost with a colony on the planet, the Marines are deployed to investigate. Though the Marines are fighting aliens, the interplay between the soldiers is incredibly realistic - it's basically a contemporary war movie with monsters.
Children of Men
Children of Men isn't really a military science fiction film by any stretch of the imagination, but it does include several scenes where we see a futuristic military, one that is far closer to our present than any of the other entries on this list. In a battle that culminates towards the end of the film, there is a long, single-take running gun battle as UK forces enter a holding area for immigrants in order to track down a terrorist cell, the Fishes. Here, we see that these soldiers are using fairly similar kit to what is used today, but there are also small communications devices and heads-up displays, elements that will likely enter the battlefield in our lifetimes.
The Halo games owe a lot to many of the entries on this list, from Starship Troopers to Aliens, to other works, such as Ringworld. Humanity has come under attack by a coalition known as the Covenant, a group of religious alien species, who deem that humanity is against their religion and seek to wipe them out. War breaks out and the games follow Master Chief, a 'Spartan Warrior' - an enhanced soldier in a power suit. The three games follow Master Chief on the first Halo ring discovered, where they also come across a zombie-like race of biological experiments known as the Flood, and then to Earth, as that falls under attack. A run-of-the-mill shooter, this game is still fun to play. We're all just waiting for Peter Jackson to get going on his film adaptation of it.
StarCraft is a real-time strategy franchise that started over ten years ago. Players can pick three species, Terrans (humans), the Zergs (insectoids) and the Protoss (humanoids). The game takes place in future, where Earth is overpopulated and has thus expanded, and as this happens, contact with alien races inevitably goes wrong, and war breaks out. The game has been hailed as one of the most influential and important games in the genre, and has remained popular since.