"Black Boomerang" by Sefton Delmer recounts his experiences in psychological warfare against Nazi Germany during World War II. Delmer, a British journalist with deep ties to Germany, details his work creating and running "black propaganda" operations, primarily through counterfeit radio broadcasts. These broadcasts, such as Gustav Siegfried Eins and Soldatensender Calais, aimed to undermine German morale by disseminating misinformation disguised as authentic German sources. Delmer explains the strategies, tactics, and personalities involved in these operations, emphasizing their impact on German society and military. The book serves as a memoir of his wartime activities and an attempt to dispel the myth of a "good Wehrmacht," revealing how propaganda shaped perceptions of the war.