Contemporaries and historians often blame the errors and tragedies of US policy during the Cold War on a dominant narrative of national security: the “Cold War consensus.” Its usual periodization, according to which it came together in the late 1940s and persisted until the late 1960s when it unraveled amidst the trauma of the Vietnam War, fits well with a common theory of change in ideas and discourse. That theory expects stasis until a substantial unexpected failure (in this domain, military defeat) discredits dominant ideas and unsettles dominant coalitions. However, systematic data reveal the standard history of this important case to be wrong. Based on a large-scale content analysis of newspaper editorials on foreign affairs, this article shows that the Cold War narrative was narrower than conventional accounts suggest, that it did not coalesce until well into the 1950s, and that it began to erode even before the Vietnam War's Americanization in 1965. To make sense of this puzzle, I develop an alternative theory of the rise and fall of the narratives that underpin and structure debate over national security. Rooted in the dynamics of public narrative and the domestic politics of the battlefield, the theory argues that military failure impedes change in the narrative in whose terms government officials had legitimated the mission, whereas victory creates the opportunity for departures from the dominant narrative. Process-tracing reveals causal dynamics consistent with the theory: failure in the Korean War, which might have undermined Cold War globalism, instead facilitated the Cold War narrative's rise to dominance (or consensus); and the triumph of the Cuban Missile Crisis made possible that dominant narrative's breakdown before the upheaval of Vietnam. This hard and important case suggests the need to rethink the relationship between success, failure, and change in dominant narratives of national security—and perhaps in other policy domains as well.