Lasers? You know how terrible those would be in space as weapons? :lol The law of conservation of energy would utterly render them useless at anything beyond "knife fight" range in space. Because every second it travelled, it would lose significant chunks of power to dissipation. Yes, it moves at the speed of light. No, that still isn't fast enough in space.

[I]If[/I] you were to engage in space, it would only be against planets, because planets are the only things that can't really dodge whatever you fire at them. Even then, a planet probably has vastly more defences to wage against an incoming fleet than the fleet could muster against it.

Space battles in space, if we are talking hard sci-fi, just would not happen.

Soft sci-fi, it could go in any direction, though.