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Forty-four years ago, and about 200 yards from where I am now standing, mankind generated its first self-sustained and controlled nuclear chain reaction. Enrico Fermi's crude atomic pile was the prototype for all that followed both reactors to generate energy for peaceful uses, and weapons of ever-increasing destructiveness. Seldom are we able to mark the beginning of a new era in human affairs so precisely.

I'm not here tonight to announce the end of that era. But I will suggest that we may be on the verge of important changes in our approach to the role of nuclear weapons in our defense. New technologies are compelling us to think in new ways about how to ensure our security and protect our freedoms. Reykjavik served as a catalyst in this process. The President has led us to think seriously about both the possible benefits and the costs -- of a safer strategic environment involving progressively less reliance on nuclear weapons. depend on whether we are far-sighted enough to proceed towards such a goal in a realistic way that enhances our security and that of our allies.

Much will now

It may be that we have arrived at a true turning point. The nuclear age cannot be undone or abolished; it is a permanent reality. But we can glimpse now, for the first time, a world freed from the incessant and pervasive fear of nuclear devastation. The threat of nuclear conflict can never be wholly banished, but it can be vastly diminished -- by careful but drastic reductions in the offensive nuclear arsenals each side possesses. It is just such reductions -- not limitations in expansion, but reductions -- that is the vision President Reagan is working to make a reality.

Such reductions would add far greater stability to the U.S.-Soviet nuclear relationship. Their achievement should

make other diplomatic solutions obtainable, and perhaps lessen the distrust and suspicion that have stimulated the felt need for such weapons. Many problems will accompany drastic reductions: problems of deployment, conventional balances, verification, multiple warheads, and chemical weapons. task ahead is great but worth the greatest of efforts.

The

This will not be a task for Americans alone. We must

engage the collective effort of all of the Western

democracies. And as we do, we must also be prepared to explore

cooperative approaches with the Soviet Union, when such

cooperation is feasible and in our interests.

The Evolution of our Thinking About Nuclear Weapons

Let me start by reviewing how our thinking has evolved about the role of nuclear weapons in our national security.

In the years immediately after Fermi's first chain-reaction, our approach was relatively simple. The atomic bomb was created in the midst of a truly desperate struggle to preserve civilization against fascist aggression in Europe and Asia. There was a compelling rationale for its development and

use.

But since 1945

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and particularly since America lost its monopoly of such weapons a few years later

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we have had to

We have

Nuclear

adapt our thinking to less clearcut circumstances. been faced with the challenges and the ambiguities of a protracted global competition with the Soviet Union. weapons have shaped, and at times restrained, that competition; but they have not enabled either side to achieve a decisive advantage.

Because of their awesome destructiveness, nuclear weapons have kept in check a direct U.S.-Soviet clash. With the advent in the late 1950's of intercontinental-range ballistic missiles

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a delivery system for large numbers of nuclear weapons at great speed and with increasing accuracy both the United States and the Soviet Union came to possess the ability to mount a devastating attack on each other within minutes.

The disastrous implications of such massive attacks led us to realize, in the words of President Kennedy, that "total war makes no sense." And as President Reagan has reiterated many times: "a nuclear war cannot be won and must never be fought"

- words that the President and General Secretary Gorbachev agreed on in their Joint Statement at Geneva a year ago.

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by the threat of

Over the years, we sought

Thus, it came to be accepted in the West that a major role of nuclear weapons was to deter their use by others as well as to deter major conventional attacks their use in response to aggression. through a variety of means and rationales "massive retaliation" in the 1950's up through "flexible response" and "selective nuclear options" in the 1970's maintain a credible strategy for that retaliatory threat.

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beginning with

-- to

At the same time, we also accepted a certain inevitability about our own nation's vulnerability to nuclear-armed ballistic missiles. When nuclear weapons were delivered by manned bombers, we maintained air defenses. But as the ballistic missile emerged as the basic nuclear delivery system, we virtually abandoned the effort to build defenses. After a spirited debate over anti-ballistic missile systems in the late 1960's, we concluded that on the basis of technologies now twenty years old -- such defenses would not be effective. So

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our security from nuclear attack came to rest on the threat of retaliation and a state of mutual vulnerability.

In the West, many assumed that the Soviets would logically see things this way as well. It was thought that once both sides believed that a state of mutual vulnerability had been achieved, there would be shared restraint on the further growth of our respective nuclear arsenals.

It was

The ABM Treaty of 1972 reflected that assumption. seen by some as elevating mutual vulnerability from technical fact to the status of international law. That Treaty established strict limitations on the deployment of defenses against ballistic missiles. Its companion Interim Agreement on strategic offensive arms was far more modest. SALT I was conceived of as an intermediate step towards more substantial future limits on offensive nuclear forces. It established only a cap on the further growth in the numbers of ballistic missile launchers then operational and under construction. The most important measures of the two sides' nuclear arsenals numbers of actual warheads and missile throw-weight restricted.

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were not

But controlling the number of launchers without limiting warheads actually encouraged deployment of multiple warheads called MIRVS on a single launcher. This eventually led to

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by

an erosion of strategic stability as the Soviets proliferating MIRVS - became able to threaten all of our

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Intercontinental Ballistic Missiles with only a fraction of their own. Such an imbalance makes a decision to strike first seem all the more profitable.

During this postwar period, we and our allies hoped that American nuclear weapons would serve as a comparatively cheap

offset to Soviet conventional military strength. The Soviet Union, through its geographic position and its massive mobilized conventional forces, has powerful advantages it can bring to bear against Western Europe, the Mideast and East Asia

- assets useful for political intimidation as well as for potential military aggression. The West's success or failure

in countering these Soviet advantages has been, and will continue to be, one of the keys to stability in our postwar world.

Our effort to deter a major Soviet conventional attack through the existence of opposing nuclear forces has been successful over the past four decades. It gave the industrialized democracies devastated by the Second World War the necessary "breathing space" to recover and thrive. there has also been recurring debate over the credibility of this strategy, as well as controversy about the hardware required for its implementation.

But

Over time, we and our allies came to agree that deterrence required a flexible strategy combining both conventional and nuclear forces. This combined strategy has been successful in avoiding war in Europe. But our reliance for so long on nuclear weapons has led some to

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forget that these arms are not an inexpensive substitute for fully facing up to mostly paid for by the United States the challenges of conventional defense and deterrence.

Sources of Strategic Instability

The United States and our allies will have to continue to rely upon nuclear weapons for deterrence far, far into the future. That fact, in turn, requires that we maintain credible and effective nuclear deterrent forces.