ABSTRACT While there is a large body of literature concerned with understanding terrorist attacks and the reasons for why they could not be prevented, this article looks at it from the opposite side: why could terrorist attacks successfully be prevented and what role did intelligence-sharing play? The article analyses three historical cases in depth based on extensive archival records from 18 intelligence agencies. This article traces how intelligence-sharing worked by highlighting the hands-on experiences of intelligence practitioners. The contribution of this article is twofold. First, the article shows how intelligence officers managed to establish successful and effective counterterrorism cooperation in the early 1970s. Second, through the eyes of intelligence reports the article presents new insights about terrorist tactics and terrorism innovation at the time. This included the use of women in terrorist plots and car sales as cover business for terrorism financing. The article concentrates on a peak moment in European terrorism history: it analyses early 1970s Black September attacks and the efforts of intelligence agencies to counter them.