Using French President de Gaulle's March 1966 threat to leave NATO as a starting point, this book tells a three-fold story. First, it gives a penetrating analysis how the North Atlantic Alliance has coped with the nuclear revolution and has overcome the crisis of credibility in European-American relations when the strategy of massive retaliation had lost its usefulness. Second, it reports how the disagreements in NATO were finally resolved and a new strategic concept (MC 14/3) was adopted, agreement on force planning, troop stationing and offset achieved, a formula for nuclear consultation found, and the Harmel Report on the management of East-West detente accepted. Third, it challenges some of the dominant theoretical explanations by structural realists and liberal institutionalists relating to alliance cohesion against the empirical findings of the case studies.