Flexible response

Flexible response calls for mutual deterrence at strategic, tactical, and conventional levels, giving the United States the capability to respond to aggression across the spectrum of war, not limited only to nuclear arms.

The New Look policy, though initially useful, quickly became obsolete with the introduction of inter-continental delivery systems that undermined the credibility of a deterrence threat.

During his presidential campaign, John F. Kennedy claimed that the Republican Party had allowed the U.S. to fall behind the Soviets into a missile gap.

Upon entering office Kennedy cited General Maxwell Taylor's book The Uncertain Trumpet to Congress for its conclusion that massive retaliation left the U.S. with only two choices: defeat on the ground or the resort to the use of nuclear weapons.

Advisers persuaded Kennedy that having multiple options would allow the president to apply the appropriate amount of force at the right place without risking escalation or losing alternatives.

The Kennedy doctrine did not include the ability to fight nuclear wars because of the idea that it would undermine deterrence, was technologically unworkable, would fuel the arms race, and was not politically feasible.

The new NATO Strategic Concept, MC 14/3, approved at the end of 1967, envisaged three types of military responses to aggression against NATO: Direct defense: In case of a conventional Soviet attack (meaning non-nuclear therefore not considered a first strike) initial efforts would be to try to stop the Soviet advance with conventional weapons.

Part of Flexible response was the strategy of being able to fight over the entire spectrum of violence by developing diverse forces for different types of warfare.

Deterrence depended on influence to show that violence and aggression did not pay, and being explicit about the level of destruction the US was willing to inflict on the enemy was one way to illustrate this point.