What qualifies a book as Military SciFi? Or better yet: What makes a story a GOOD Military SciFi story? 
Wikipedia describes it like this: “Military science fiction is a subgenre of SciFi that features the use of SciFi technology, mainly weapons, for military purposes and usually principal characters that are members of a military organization involved in military activity; occurring sometimes in outer space or on a different planet or planets.” 
I am happy with that description. Military SciFi, as basic as this sounds, involves primary characters who are based within the military and are engaged in some form of military conflict. Typically you’ll experience that war from the every day soldier’s point of view, and often that soldier will climb through the ranks so that you can experience the war from multiple levels. This leaves room for a lot of character development to happen, and in good Military SciFi that development happens.  
There it is again: GOOD Military SciFi. What sets the best stories apart from the rest? Well that is a highly subjective question, and fortunately I enjoy subjective questions! 

  
Good Military SciFi features technology, but focuses on humanity. It is a human story designed to look into the heart of humanity and warfare. Yes we want to read about the cool space guns and space ships but the story can’t be a tech manual. That’s boring and ultimately becomes outdated quickly. Good Military SciFi looks deep into us, into what makes us human, what drives us, what breaks us, and ultimately how we find the will to persevere. The cool technology sets the stage for the players to act, it isn’t meant to be the play itself.

  
Good Military SciFi should include diversity of some form. The military has often been a leader in areas of integration and diversity. It has had successes and failures but in theory it is a place where you excel based on character, deeds, and abilities. However good Military SciFi can showcase the struggle minorities face to be known for their abilities, or show a non minority character facing, acknowledging, and advancing beyond their inner prejudices. It isn’t a prerequisite of Military SciFi but the best ones do address the issue of diversity.  And we need more diversity in books.

  
Good Military SciFi deals with the moral dilemma of warfare. War is not pretty, and it is not easy, and it comes with a high cost both to the victors and the defeated. Good Military SciFi recognizes this and addresses the cost of war on the people waging it and the nation state behind them. War brings out the best and the worst in us. This fact shouldn’t be ignored. 

  
Good Military SciFi involves ambiguity. The fog of war envelops not just the plot but also the hearts and minds of the characters. Everything shouldn’t be tied up into a neat little package for the reader. The reader should have to invest in the story alongside the characters and reach their own conclusions about the dilemmas facing them. 

  
The best Military SciFi involves sacrifice. These tales should be cautionary tales designed to help us understand the high cost of war and one of those costs is sacrifice. The willingness to put your life on the line in front of others is a part of the military mindset, and often that sacrifice is required for the good of the many. 

  
Military SciFi is also about the camaraderie that military service develops. Oftentimes you’ll hear veterans attest that the primary reason they fought and held a position was for the soldier next to them. They fought, bled, and sacrificed for each other. 

  
In my eyes good Military SciFi includes a look at the technology, the trappings of the military, the training, and the actual warfare, but it goes beyond that to teach us a lesson about ourselves. About humanity. About what our soldiers face, and about our responsibility to our veterans. It lets us look into human nature and either help us understand humanity better or at least learn some of the questions about humanity that we should be asking.  
And it tells a damn good story.