The first casualty of war

If truth really is the first casualty of war, how do we know if any war is truly worth the cost in lives and treasure?  Be it by lies, propaganda or by legitimate means, we are always led to believe that our country's military efforts are positive; that we are fighting the good war, and that the other side must be demonized.  This history of American war propaganda is told in Susan A. Brewer's Why America Fights: Patriotism and War Propaganda from the Philippines to Iraq. My conversation with Susan Brewer.