Most of these techniques were developed during World War II or earlier, and have been used to some degree in every conflict since. Daniel Lerner was in the OSS (the predecessor to the American CIA) and in his book, attempts to analyze how effective the various strategies were. He concludes that there is little evidence that any of them were dramatically successful, except perhaps surrender instructions over loudspeakers when victory was imminent. Measuring the success or failure of psychological warfare is very hard, as the conditions are very far from being a controlled experiment.