The Eldraeverse

Colony Drop: One of the standard military tactics for softening up a planet, but also one that is horribly, horribly illegal (in the Ley Accords/Laws and Customs of War sense of Do This And We Kill You) if done with large rocks, or lots of rocks, on any world with an ecosystem.  Once again, ecosystems are expensive.

(This doesn’t stop a lot of people from using it in the Mutually Assured Destruction sense with relativistic k-kill vehicles, on the fairly reasonable grounds that the already dead don’t have to worry about interstellar law.)