One interesting case is the Yom Kippur War. Groupthink was broadly attributed as a major factor in why the Israel Defence Force's intelligence unit failed to foresee the surprise attack that started the war, despite very clear signs leading up to it [1].<p>As a safeguard, the structure of the organization was changed significantly, including the creation of a "devil's advocate" office, whose task is basically to criticize assessments coming from the main group.<p>From a Brooking's Institution report [2]:<p><i>The devil’s advocate office ensures that AMAN’s intelligence assessments are creative and do not fall prey to group think. The office regularly criticizes products coming from the analysis and production divisions,and writes opinion papers that counter these departments’ assessments. The staff in the devil’s advocate office is made up of extremely experienced and talented officers who are known to have a creative, “outside the box” way of thinking. Perhaps as important, they are highly regarded by the analysts. As such, strong consideration is given to their conclusions and their memos go directly to the office of the Director of Military Intelligence, as well as to all major decision makers.</i><p><i>The devil’s advocate office also proactively combats group think and conventional wisdom by writing papers that examine the possibility of a radical and negative change occurring within the security environment. This is done even when the defense establishment does not think that such a development is likely, precisely to explore alternative assumptions and worst-case scenarios.</i><p>[1] <a href="http://en.wikipedia.org/wiki/Yom_Kippur_War#Lead-up_to_the_surprise_attack" rel="nofollow">http://en.wikipedia.org/wiki/Yom_Kippur_War#Lead-up_to_the_s...</a><p>[2] <a href="http://www.brookings.edu/~/media/research/files/papers/2007/10/intelligence%20kuperwasser/10_intelligence_kuperwasser.pdf" rel="nofollow">http://www.brookings.edu/~/media/research/files/papers/2007/...</a>