Militaries, and the U.S. military in particular, envisions a future where weapons do the thinking -- that is, planning, target selection and engagement. If we are not careful about the increasing push towards autonomous weapons, we may lose our very humanity in the process.
The U.S. Department of Defense wants to enlarge the U.S. military's reliance on autonomous (i.e. self-directed) weapons in conflict. But a mission is not a person, it is a thing, and things cannot be held morally responsible. It is like saying that you want to hold your car responsible for breaking down on the way to work. You wouldn't say that your car "wronged" you, and you wouldn't seek to punish your car. Such a position on the ethics of autonomous systems reduces any questions of morality or responsibility.