Quote Originally Posted by Mastikator View Post
I'm assuming "hard science" sci-fi.
In a sci-fi setting it's unlikely that there'd be actual soldiers or small fighter vessels. Instead it'd be an arms race of whoever can build the biggest most powerful and advanced space ship.

Also, keep in mind that the law of accelerating returns combined with the fact that races don't develop simultaneously would dictate that all races would be on each level of the Kardashev scale. So if there is any race above humans they'd be so far above and beyond humans might not even know of their existence.
It really all stands and falls with faster than light travel and communication. Statistically there are probably hundreds or thousands of species at a similar technological level as humans, but finding and reaching them is the hard part.
Species without the technological ability to meking themselves "heard" would be almost undetectable, so it would make sense that almost all known species have advanced at least to a certain level of physics and technology.