Imagine being able to select from any number of available comets/asteroids... size, mass, composition... and then direct it where you want it to go. It might take a little while to find just the right one, on a course you can alter to suit your needs, but once you do that, your enemies can be wiped off the map. And nobody knows it was you that did it.

"We need to develop the ability to steer stuff in space... for safety!" Yeah, for safety, that's it.