More and more war is coming to be looked upon as in itself a lamentable and evil thing. A wanton or useless war, or a war of mere aggression--in short, any war begun or carried on in a conscienceless spirit, is to be condemned as a peculiarly atrocious crime against all humanity.
 Theodore Roosevelt, State of the Union Address. copy citation

Context

“This Government will do everything in its power to secure the success of the conference, to the end that substantial progress may be made in the cause of international peace, justice, and good will.
This renders it proper at this time to say something as to the general attitude of this Government toward peace. More and more war is coming to be looked upon as in itself a lamentable and evil thing. A wanton or useless war, or a war of mere aggression--in short, any war begun or carried on in a conscienceless spirit, is to be condemned as a peculiarly atrocious crime against all humanity. We can, however, do nothing of permanent value for peace unless we keep ever clearly in mind the ethical element which lies at the root of the problem. Our aim is righteousness. Peace is normally the hand-maiden of rightousness; but when peace and righteousness conflict then a great and upright people can never for a moment hesitate to follow the path which leads toward righteousness, even though that path also leads to war.” source