Irving Janis coined the term groupthink in 1972 following his analysis of a sequence of catastrophic foreign policy decisions — the Bay of Pigs invasion, the failure to anticipate Pearl Harbor, the escalation of the Vietnam War — that shared a structural similarity. The decision-makers were intelligent. The information needed to avoid the mistake was, in most cases, available within the group. And the consensus was wrong. Janis identified the mechanism: in groups with high cohesion and high external pressure, the social cost of dissent becomes high enough that members suppress their reservations, validate one another’s assumptions rather than challenging them, and arrive at a convergence that none of them, individually, would necessarily have endorsed.