||This article relies largely or entirely upon a single source. (February 2011)|
Massive retaliation, also known as a massive response or massive deterrence, is a military doctrine and nuclear strategy in which a state commits itself to retaliate in much greater force in the event of an attack.
In the event of an attack from an aggressor, a state would massively retaliate by using a force disproportionate to the size of the attack.
The aim of massive retaliation is to deter an adversary from initially attacking. For such a strategy to work, it must be made public knowledge to all possible aggressors. The adversary also must believe that the state announcing the policy has the ability to maintain second-strike capability in the event of an attack. It must also believe that the defending state is willing to go through with the deterrent threat, which would likely involve the use of nuclear weapons on a massive scale.
Massive retaliation works on the same principles as mutually assured destruction, with the important caveat that even a minor conventional attack on a nuclear state could conceivably result in all-out nuclear retaliation.
In August 1945, the United States ended World War II with the nuclear attacks on Hiroshima and Nagasaki in Japan. Four years later, on August 9, 1949, the Soviet Union developed its own nuclear weapons. At the time, both sides lacked the means to effectively use nuclear devices against each other. Eventually with nuclear triads being established, both countries were quickly increasing their ability to deliver nuclear weapons into the interior of the opposing country.
We need allies and collective security. Our purpose is to make these relations more effective, less costly. This can be done by placing more reliance on deterrent power and less dependence on local defensive power... Local defense will always be important. But there is no local defense which alone will contain the mighty landpower of the Communist world. Local defenses must be reinforced by the further deterrent of massive retaliatory power. A potential aggressor must know that he cannot always prescribe battle conditions that suit him.
Dulles also said that the U.S. would respond to military provocation "at places and with means of our own choosing." This speech and quotes appear to form the basis for the term massive retaliation, which would back up any conventional defense against conventional attacks with a possible massive retaliatory attack involving nuclear weapons.
The doctrine of massive retaliation was based on the West's increasing fear at the perceived imbalance of power in conventional forces, a corresponding inability to defend itself or prevail in conventional conflicts. By relying on a large nuclear arsenal for deterrence, President Eisenhower believed that conventional forces could be reduced while still maintaining military prestige and power and the capability to defend the western bloc.
Upon a conventional attack on Berlin, for instance, the United States would undertake a massive retaliation on the Soviet Union with nuclear weapons. The massive response doctrine was thus an extension of mutually assured destruction to conventional attacks, conceivably deterring the Soviet Union from attacking any part of the United States' sphere of influence even with conventional weapons.
In theory, as the U.S.S.R. had no desire to provoke an all-out nuclear attack, the policy of massive response likely deterred any ambitions it would have had on Western Europe. Although the United States and NATO bloc would be hard-pressed in a conventional conflict with the Warsaw Pact forces if a conventional war were to occur, the massive response doctrine prevented the Soviets from advancing for fear that a nuclear attack would have been made upon the Soviet Union in response to a conventional attack.
It can be argued, however, that aside from raising tensions in an already strained relationship with the Soviet bloc, massive retaliation had few practical effects. A threat of massive retaliation is hard to make credible, and is inflexible in response to foreign policy issues. Everyday challenges of foreign policy could not be dealt with using a massive nuclear strike. In fact, the Soviet Union took many minor military actions that would have necessitated the use of nuclear weapons under a strict reading of the massive retaliation doctrine.
A massive retaliation doctrine, as with any nuclear strategy based on the principle of mutually assured destruction and as an extension the second-strike capability needed to form a retaliatory attack, encourages the opponent to perform a massive counterforce first strike. This, if successful, would cripple the defending state's retaliatory capacity and render a massive retaliation strategy useless.
Also, if both sides of a conflict adopt the same stance of massive response, it may result in unlimited escalation (a "nuclear spasm"), each believing that the other will back down after the first round of retaliation. Both problems are not unique to massive retaliation, but to nuclear deterrence as a whole.
Policy shift 
President John F. Kennedy abandoned the policy of massive retaliation during the Cuban Missile Crisis in favor of flexible response. Under the Kennedy Administration, the U.S. adopted a more flexible policy in an attempt to avert nuclear war if the Soviets did not cooperate with American demands. If the United States' only announced military reaction to any Soviet incursion (no matter how small) were a massive nuclear strike, and the U.S. didn't follow through, then the Soviets would assume that the United States would never attack. This would have made the Soviet Union far more bold in its military ventures against U.S. allies and would probably have resulted in a full-scale nuclear war. By having other, more flexible policies to deal with aggressive Soviet actions, the U.S. could opt out of a nuclear strike and take less damaging actions to rectify the problem without losing face in the international community.
See also 
- Massive Retaliation at the Nuclear Files