Some issues of interest on this topic:<br /><br />First, the delay time. Rods from God might be effective, but let's not forget the delay between release and impact. Not to mention, of course, that a rod carried on a weapons satellite shares that satellite's orbital velocity (~7.7km/sec for LEO). If you just "let go" of it, it will stay exactly where it is in relation to the satellite. Accelerating it towards the planet will just give it a more eccentric orbit, so what you need to do is accelerate it back along your orbit enough to de-orbit it. Naturally, this will boost the orbit of the weapons satellite, meaning subsequent firings will need more kick to achieve the same effect.<br /><br />This would be feasible for hitting stationary targets, but not so much for tactical assistance on a battlefield. Rods from God, then, are pretty much strategic weapons only.<br /><br />Using a laser would solve both the delay and the velocity problems, but now you've got beam dispersion in the atmosphere to contend with. Not to mention the fairly large energy requirement to do real damage to something - you'll need an impressive power plant on your weapons platform.<br /><br />So let's talk about moon-based weapons.<br /><br />Well, first up, if you're going to launch something from the moon at the planet, you need to achieve escape velocity from the moon - a little more than 2km/s. Done properly, this will also take care of the moon's orbital velocity (~1km/s). Now you've got a significant delay time to contend with, since you've got to cover more than 350,000km. If I'm solving my motion equations correctly, the object will take more than 140 minutes to hit the planet (and that's assuming that earth's gravity is 9.8N out at lunar orbit, which is false). Now, its terminal velocity will be pretty hot: ~83km/s (for comparison, the Tunguska comet is figured to have entered at ~60km/s), ignoring atmospheric drag. That works out to 3.4E9 joules per kg of mass. A megaton is 4.184E15 joules, so e