Psychological warfare, with propaganda as one of its principal instrument, emerged in World War I as a lethal force which in some ways was comparable to technological advances in weaponry. Just as aerial bombing, deadly gases and modern arms marked a new era in whole-sale killing, so propaganda was a milestone in the battle of warring nations to control public opinion. The war did not usher in propaganda; its roots have been traced back to the Crusades and beyond. It was the Great War, however, that produced the beginnings of today\u27s sophisticated propaganda techniques. So effective, in fact, was World War I propaganda that some scholars hold it chiefly responsible for America\u27s decision to take up arms against Germany
