9-11 represented a crucial event in international politics. It took the world’s only superpower by surprise. How was it possible? This paper investigates the causes of that intelligence failure. It refers to three complementary “cuts”. First, it examines cognitive and psychological factors such as the «signal to noise ratio» problem, overconfidence, wishful thinking, lack of imagination, “cry wolf” syndrome, confirmation bias. Second, it pays attention to organizational complexity and ragmentation, problems of coordination, inter- and intra-organizational competition, with an emphasis on the role of the CIA and the FBI. Third, it takes the responsibility of decisionmakers into account, by examining the problem of the government response to warning, policy failures and drawbacks arising from overcrowded agendas, competing priorities and political electoral interests.