Which long career as a military science fiction writer? I admit aside ASOIAF I haven't read much GRRM -- his awesome Sandkings short story, and his collaborati

Which long career as a military science fiction writer? I admit aside ASOIAF I haven't read much GRRM -- his awesome Sandkings short story, and his collaboration with Lisa Tuttle, Windhaven, and I'm aware of some of his horror/fantasy fiction. Checking on Wikipedia I don't see a lot of military scifi in the list...