200 years ago War Fighting hardly killed any civilians at least directly.....WW1 did not. WW2 got the civilian killing off the ground by the Brit and American bombing of German cities....it has not slowed that much since.
Ever hear of the Battle Of Britain?
Honestly.
doesn't matter, they're still legitimate targets.
When war is duly declared, it is not merely a war between this and the adverse government in their political characters. Every man is, in judgment of law, a party to the acts of his own government, and a war between the governments of two nations, is a war between all the individuals of the one, and all the individuals of which the other nation is composed. Government is the representative of the will of all the people, and acts for the whole society. This is the theory in all governments, and the best writers on the law of nations concur in the doctrine, that when the sovereign of a state declares war against another sovereign, it implies that the whole nation declares war, and that all the subjects of the one, are enemies to all the subjects of the other. Very important consequences concerning the obligations of subjects, are deducible from this principle.
James Kent, Commentaries
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IMHO, the government really screwed the pooch on 'legitimate war' since it has no legal authority to declare war on an ideology.