[quote=Brovo]
Realistically speaking, space warfare is not a matter of stealth in the traditional sense of "invisibility", and combat would not be done in the traditional sense of ballistics-based warfare. The rule of thumb is nothing can travel faster than light.Ergo, from an admittedly primitive point of view, space combat would likely be more on a planetary scale. Missiles would be countered long before they could reach their targets by this point so it would be more like spies with suit case explosives. The idea of large fleets doing battle would become, frankly, antiquated, in an era where a planet loaded with self-defense platforms and satellites would be more than capable of evaporating fleets of thousands of war ships.Wars would be fought in the dark by diplomats, politicians, assassins, and sabotage. Embargos would become the new method by which to exclude a member of the community. Speaking of community, there would only be a very shrewd sense of it. By the time messages would get to and from the Earth, years will have passed, decades, possible even centuries. Dreams of empire would be fantastical at best. Even defeating the speed of light for data and messages, there would be no way to enforce threats unless you could defeat the light speed barrier with ships as well. At which point, you've hit the event horizon that keeps "hard" sci-fi where it is, and begin to move into the soft sci-fi realm.There's not much else to say about it.
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Not necessarily. Planet-to-orbit is a massive energy barrier (I mean you've seen how much rocket it takes to put a shuttle into LEO). Planet-to-interstellar missiles would have to be... I mean.... we're talking *enormous* amounts of power required. The more logical process would be to send tools of production into space -- something like a construction drone, sent out into the asteroid belt to convert space rocks into materials, materials into space stations, stations into shipyards, etc. So what's the advantage of doing something like that, well, A, it dramatically reduces how much mass you need to carry off your planet, which is a big deal. But secondly, it opens the door for space travel as a means of power-projection. Think 'carrier battlegroups' in naval theory.... Carriers are essentially portable airfields, and massive ships like these would function as portable planets. You'd park it in orbit around a sun, and you'd immediately enjoy vast physical advantages over any planet-bound (or planet-orbiting) forces in the system -- primarily, firing weapons from a ship will always consume less energy than firing weapons from a planet, because of gravitational considerations. 

So, if you can BUILD such a ship -- which only a select few could, on account of (again) physical barriers to access and the costs involved -- you could very conceivably use them to build an empire. For reference the British built a global empire in an era of sailboats and carrier pigeons... these things are certainly possible, for the men who can pull it off.