Okay, I have some questions about certain physics and limitations. 

Light takes time to travel. The distance from the earth to the moon is roughly a second, but from the sun to the earth takes a little over 8 minutes.. and from earth to mars takes about 40 minutes. 

LASER - light amplification by stimulated emission of radiation - Is essentially a columnated spatially and temporally coherent beam of EM radiation, usually in the infrared or ultraviolet range. Of course there are radio wave variations and the like. Granted there's little to disrupt the beam, but the lag time for the beam to travel would make super-long range shooting a virtual impossibility, say something more than 600,000 kilometers for anything smaller than a long range (intra-system ship, say designed to fly to pluto and back), unless flying a stable course in a straight line at a specific rate of travel.

Another thought is, there was recently a laser system designed that creates a laser that has the same output as the sun for a brief moment with an interesting form of optical condensing and compression. Would something not be similarly possible with military grade lasers of the day? All that much energy packed into a single shot would be nasty. 

Also, what about microwave lasers? 

Also, are you taking in communications and sensor lag, as well as power degradation over distance? 

What kind of accelleration do missiles have available. 20g's? 50 g's? 100 g's? While it might take a laser a second or two to reach lunar distances, a missile pulling 100+ g's of acceleration could reach that distance almost as quickly, and outfitted with a nuke, or even one that splits into multiple warheads could be nasty. 

Also, what about particle accelerators, or particle beams. A muon beam might be more effective against a target than a laser, and most particle beams cause a catastrophic failure of most materials they hit, while (as far as I know) inflicting little heat inclination. 

Random Question - Have you ever read First Flight or the Sundowner Trilogy by Chris Claremont? (awesome series, some of this I'm actually taking notes from since it's a fairly hard sci-fi setting and similar to this setting.)