Make it harder to engage in military action without demonstrable justification, as well as introduce tri-partisan reviews of military action, as it progresses, to determine whether the action is and continues to be necessary.
If a determination is made that an action has gone awry, or is found to be unjustified after the fact, they would be authorized to hold accountable, in a serious manner, the men and women making the root decisions that launched the action.
With great power comes great responsibility. Or at least that is what I have always been told by people with great power... ಠ_ಠ