"Back in the twentieth century, they had established to everybody's satisfaction that 'I was just following orders' was an inadequate excuse for inhuman conduct... but what can you do when the orders come from deep down in that puppet master of the unconscious?"
-- Joe Haldeman, The Forever War
With war at the top of the news, I found myself thinking of Joe Haldeman's Hugo- and Nebula-award winning novel The Forever War. It's sometimes shorthanded as an anti-war novel, but importantly, I never felt the soldier characters were treated as straw men, at least as far as my years-old recollection tells me. Rather, the effects of war are shown in the toll it takes on the warriors, a reality that Haldeman, a Vietnam veteran, experienced firsthand. This immediacy puts The Forever War in the company of such soldier-authored books as The Things They Carried which dramatize the damage war does its veterans in body and mind.
The Forever War tells the story of a centuries-long interstellar struggle between humanity and the mysterious Taurans, all through the eyes of a single soldier, William Mandella. Haldeman uses a clever device to let his viewpoint character see the long span of the war, and the story is built around it.
In the universe of the novel it's discovered that collapsars (another name for black holes, although I'm not 100% clear if Haldeman is referring to the same thing here) can safely be used as gateways between different parts of the galaxy. This allows for a kind of faster-than-light drive, but an entirely natural one, and one which humans can exploit but not reproduce. Where this would have big implications for travelers is twofold, and both related to Einstein's theories of relativity: getting near a black hole puts you in regions of spacetime where your personal time slows relative to Earth's, and just getting to a black hole requires ships moving close to the speed of light, which also slows down the passage of time for the traveler.
Of necessity then, an interstellar soldier is estranged from the home front, because he (or she) is a historical relic after just one mission.
This isn't just interestingly science fictional, it ramps up the real-world disconnect veterans experience on returning from wars. And usefully for storytelling, it lets a single voice cover centuries of conflict. Mandella's personal story is also a history of the Tauran War, from its early stages to its finish. He witnesses constant changes in technology and society, feeling more and more alienated. Only the military and the war offer any kind of stability, but at a dehumanizing cost.
The Forever War is also a love story, as Mandella's only enduring personal connection is to a fellow soldier. My strongest memory of the book is a scene in which Mandella's lover is suffering a slow but deadly injury as a result of a damaged acceleration tank. The tank should be protecting her body from the effects of high-speed maneuvers, but in fact the ship's rapid movement is killing her. I recall reading this scene alone on a night flight. I had a window seat and was pressed against a cold bulkhead, the view outside showing only the airplane's wing and the darkness. I had a vivid sense of humanity -- fleshy, bloody, and vulnerable -- hitched to fantastic and deadly machines. That harsh image of space travel has never left me, for all my romanticized ideas of adventure on other planets.
Though the novel has many dark moments, the book does reach a fairly positive conclusion, both for the couple and for a very changed humanity. But it's a grim ride.
As an aside, Haldeman's model of slower-than-light ships taking advantage of a previously existing faster-than-light network has become popular in science fiction. I can understand why. It allows the human technology to be fairly explicable within science-as-we-know-it, while still making it possible to zip characters off to distant solar systems in a relative hurry. Variations of this concept appear in Joan D. Vinge's Snow Queen cycle, Lois McMaster Bujold's Vorkosigan Saga, and Vonda N. McIntyre's Starfarers Quartet. It also appears in the roleplaying games Diaspora and Shock: Human Contact.
And speaking of games, The Forever War inspired at least two wargames: a licensed game of ground combat and Warp War, a space combat game.
Update: Added links.