Shades of Robert Heinlein’s, The Moon is a Harsh Mistress. Just “throwing rocks” at cities could cause massive damage with none the radiation that nuclear weapons have.
I just looked up kinetic orbital bombardment on wiki, it’s wiki but I didn’t realize Pournelle came up with a proposal for it when he was at Boeing in the 50’s. I had heard of THOR but I didn’t realize it was that old. I knew he and Niven used it for Footfall, but that’s probably not news for you on account of your screen name.
http://en.wikipedia.org/wiki/Kinetic_bombardment
the ‘in science fiction’ section is pretty interesting.
Freegards