I’m reading The Wisdom of Crowds, and I came across the following passage:

After a detailed study of American foreign-policy fiascos, including the Bay of Pigs invasion and the failure to anticipate Pearl Harbor, [psychologist Irving] Janis argued that when the decision makers are too much alike — in worldview and mind-set– they easily fall prey to groupthink. Homogeneous groups become cohesive more easily than diverse groups, and as they become more cohesive they also become more dependent on the group, more insulated from outside opinions, and therefore more convinced that the group’s judgment on important issues must be right. These kinds of groups, Janis suggested, share an illusion of invulnerability, a willingness to rationalize away possible counterargument to the group’s position, and a conviction that dissent is not useful.
In the case of the Bay of Pigs invasion, for instance, the Kennedy administration planned and carried out its strategy without ever really talking to anyone who was skeptical of the prospects of success. The people who planned the operation were the same ones who were asked to judge whether it would be successful or not. The few people who voiced caution were quickly silenced. And, most remarkably, neither the intelligence branch of the CIA nor the Cuban desk of the State Department was consulted about the plan. The result was a bizarre neglect of some of the most elemental facts about Cuba in 1961, including the popularity of Fidel Castro, the strength of the Cuban army, and even the size of the island itself. (The invasion was predicated on the idea that 1,200 men could take over all of Cuba)

It’s a good thing we’ve learned from our mistakes, and no presidential administration would ever silence internal dissent while making a vital foreign policy decision, leading to a major military debacle.