benEzra - the coherant nature of a laser means that it's power doesn't fall off porportionally to the square of the distance - the light stays together and spreads very little so it retains all of it's energy. On the moon, in orbit or on the next ridge over, the same laser would deliver the same amount of energy (except for what the atmosphere absorbs/reflects etc) to the target. A much bigger problem for a moon based laser would be getting it aimed precisely enough to be sure of what it was going to hit 400,000 kilometers away. Thats roughly 0.0000005 minutes of angle for an 8 inch target zone at that distance,
I can see a laser CIWS type system for ships, and a version for vehicles to protect against missles and shells. But you will still need the current bullet ammo systems for use in fog, rain, snow, dust/sand storms etc where the laser becomes useless. Current smoke screens wouldn't greatly reduce the laser since it works in the infrared region of light, and that goes through todays smokescreens fairly well. Of course the camaflauge people are already working on smoke that is opaque to infrared to hide from todays infrared goggles - and this new type of smokescreen will work against infra-red lasers as well.