Aside from the intrinsic moral problems (which should be less severe than starting a war) and risks (getting caught, especially if you fail), and setting a poor precedent, assassination isn’t particularly useful unless the person you’d be assassinating is actually the problem. Usually they aren’t.
Aside from the intrinsic moral problems (which should be less severe than starting a war) and risks (getting caught, especially if you fail), and setting a poor precedent, assassination isn’t particularly useful unless the person you’d be assassinating is actually the problem. Usually they aren’t.