In the summer heat of 1979, amid the deep freeze of the Cold War—I walked into the Kremlin with five of my Senate colleagues.
We were there to discuss the strategic arms control agreement known as SALT II—and to gauge whether or not the Soviets were likely to abide by modifications that the Senate had adopted.
I was 36-years old, in my seventh year as a United States Senator.
Across the table sat Alexei Kosygin—the grizzled Soviet Premier—a veteran of World War II and a hard-liner.
There was no love between us.
We did not trust each other.
But neither of our nations wanted to be responsible for unleashing a nuclear apocalypse.
Kosygin did most of the talking that day, and one of the first things he said to me was this reminder:
"You are the only nation in the history of mankind that has ever used nuclear weapons. I am not second-guessing that, but you used them.
So you have to understand why we think you might use them again."
I came out of that meeting with the assurances I needed, and a lesson that has served me throughout my career—the assumption of good intentions rarely extends to international diplomacy.
The Soviets wanted a deal with us not because they trusted us, but because they didn't.
It is precisely because we do not trust our adversaries that treaties to constrain the human capacity for destruction are indispensable to the security of the United States of America.
Arms control is integral to our national defense and—when it comes to nuclear weapons—to our self-preservation.
From almost the moment we unlocked the destruction of worlds hidden within the atom, we recognized the equally powerful imperative of preventing the Doomsday Clock from striking midnight.
Already in 1953, President Eisenhower—a man synonymous with American military strategy—warned that our security could never be achieved through a nuclear arms race without end:
"Let no one think that the expenditure of vast sums for weapons and systems of defense can guarantee absolute safety for the cities and citizens of any nation. The awful arithmetic of the atomic bomb does not permit any such easy solution. Even against the most powerful defense, an aggressor in possession of the effective minimum number of atomic bombs for a surprise attack could…cause hideous damage."
In a world possessed of nuclear technology, the effective minimum number of bombs is small.
Even one can cause hideous damage.
With that knowledge—over the course of decades—we negotiated agreements to reduce and control the world's supply of nuclear weapons.
Despite what some extreme voices argued at the time, the arms control agreements we hammered out with the Soviets were not concessions to an enemy or signs of weakness in the United States.
They were a carefully constructed barrier between the American people and total annihilation.
It was how we managed a dangerous rivalry, kept it from spinning out of control, and prevented thermonuclear war.
Republican and Democratic presidents alike have understood that nothing is more fundamental to our security.
And, for more than four decades, I have been deeply involved with the ins and outs of our strategic agreements.
As I said, I was a forceful advocate for SALT II in the '70s and the limits it sought to impose on the growth of the Soviet Union's nuclear capacity.
In the '80s, I fought against President Reagan's efforts to weaken the Anti-Ballistic Missile Treaty, which threatened the very cornerstone of arms control between the United States and the Soviet Union.
But I fought equally hard to make sure his Treaty on Intermediate-Range Nuclear Forces—the first treaty to eliminate a whole class of nuclear arms—would succeed. I traveled across Europe—meeting with Helmut Kohl, Francois Mitterrand, and Margaret Thatcher as well as Soviet leader Gromyko—to bolster support for the treaty.
After the collapse of the Soviet Union, I called for the global elimination of tactical nuclear weapons—a position that President George H.W. Bush also worked toward. And I made sure that the START agreement included appropriate measures to monitor nuclear stockpiles in the former Soviet Union.
Today, the risk of a massive nuclear exchange between Russia and the United States—and the terminal logic of mutually assured destruction—is far less than at the height of the Cold War.
Yet nuclear weapons—the proliferation of this deadly knowledge to more nations, and the possibility of a terrorist obtaining nuclear materials—remain among our most pressing security challenges.
Even one nuclear bomb can still cause hideous damage.
That's why, from the moment President Obama and I took office eight years ago—reducing the threat of a nuclear attack has been a chief national security priority.
In Prague in 2009—in his very first foreign policy speech—President Obama passionately argued that the only way the world will be completely safe from nuclear weapons, is to pursue a world without nuclear weapons.
And for the past eight years, that is the vision we have relentlessly pursued.
Thanks to America's leadership, the international community is newly focused on preventing nuclear terrorism. We know that terrorists have both the capacity and the goal of transforming nuclear materials into weapons to sow havoc.
And we know that no nation acting alone can defeat this threat.
That's why, in 2010, President Obama gathered leaders from around the globe for the first ever Nuclear Security Summit here in Washington—to create concrete multilateral strategies to lock down loose nuclear materials and prevent nuclear smuggling.
Since then, the world has met three more times—in Seoul, in The Hague, again last year in DC—to continue building on our progress.
Our efforts have reduced the supply of nuclear weapons-usable material in the world. And we've not only stepped up the physical protection of facilities where nuclear materials are stored—we've greatly improved our ability to detect and seize unregulated nuclear and radiological materials being smuggled in secret.
Acting together with our international partners, we've strengthened the global nuclear security architecture that monitors and enforces nuclear norms:
Ratifying and bringing into force important international treaties to secure nuclear materials and prevent them from falling into the hands of terrorists.
Providing better funding and resources for the International Atomic Energy Agency. Expanding the Proliferation Security Initiative.
These steps have bolstered the international norms and institutions around the protection of nuclear materials.
And with the creation of the Nuclear Security Contact group, the world can continue to build on this momentum to deliver progress for many years to come.
For eight years, the United States has also led in strengthening the non-proliferation regime, including the Non-Proliferation Treaty—that basic agreement that: countries with nuclear weapons will pursue good faith negotiations on disarmament, countries without nuclear weapons will not seek to gain them, and all countries can access and benefit from peaceful nuclear energy.
We built a global consensus that nuclear norms must be upheld, international commitments must be honored, and those who violate these standards must be called to account.
That's why the United States made it an international priority to prevent Iran from obtaining a nuclear weapon.
Decades of animosity and chest thumping did not cut off Iran's burgeoning nuclear program. We did—through international economic pressure combined with hard-nosed diplomacy.
As with the Soviet Union during the Cold War—we negotiated with Iran precisely because we did not, and do not, trust them.
That's why we sought an internationally verifiable agreement to constrain their nuclear activities. One that cut off every single path that could lead to a nuclear weapon—and one that instituted the most rigorous inspections regime in history to ensure they hold up their end of the deal.
If full implementation continues, the deal will prevent Iran from obtaining a nuclear weapon—and remove the threat of Iran using nuclear weapons against us or our allies. And we accomplished this without inciting another devastating war in the Middle East.
When we came to office, Iran was inching closer to a nuclear weapons capability—but North Korea had already crossed the threshold.
And as North Korea's nuclear and ballistic missile capabilities continue to expand, it poses a growing threat to international security and our own national defense.
That's why we've been so vigilant in keeping the international community united to raise the costs on North Korea for its flagrant violations of nuclear norms.
Just last year, in response to two illegal nuclear tests by North Korea, the United Nations Security Council—including China and Russia—unanimously adopted two resolutions imposing the most far-reaching and comprehensive sanctions on North Korea to date.
We need to ensure that these sanctions are enforced by all—to ensure North Korea understands that we will continue to impose costs for their illegal behavior.
As with Iran, the goal of sanctions is not to punish the people of North Korea, but to induce their leadership to negotiate in earnest.
North Korea's growing capability is one of the most significant challenges the next administration will face. There are no simple solutions.
But any viable path forward must include standing with our Asian allies to send a clear message to Pyongyang: Attempts at coercion or intimidation will fail. Security and international respect cannot be attained through illegal weapons. And as long as that is the choice North Korea's leaders continue to make, their country will remain economically isolated and an international pariah.
We must continue working closely with the international community—including China—to convince North Korea to reverse course.
As we've worked to stem the spread of nuclear weapons, we've also advanced the second half of the non-proliferation bargain: that every nation can use peaceful nuclear technology—for energy, for medical advancements, for research to better the human condition.
Again, this understanding dates back to President Eisenhower, who said: "It is not enough to take this weapon out of the hands of the soldiers. It must be put into the hands of those who will know how to strip its military casing and adapt it to the arts of peace."
We've invested significant time and energy buttressing the international framework for civil nuclear cooperation. We've taken practical steps like supporting the IAEA's Low-Enriched Uranium bank and setting up our own American fuel bank so that states are ensured reliable access to nuclear energy without setting up fuel-cycle capabilities in their own countries.
Ten years ago, I ushered our civil-nuclear cooperation agreement with India through the Senate—an agreement that will allow U.S. nuclear reactors to provide enough electricity to power New Delhi and Mumbai through peak usage in the hottest summer day.
And over the past eight years, our administration has pursued and brought into force new peaceful nuclear cooperation agreements with Russia, China, the Republic of Korea, Vietnam and others.
In total, the United States now has 22 such agreements with 47 partners resulting in the production of more than 1.5 million gigawatt hours of safe, clean nuclear power worldwide in 2015—enough to power 150 million homes for an entire year.
Of course, no discussion of nuclear weapons can ignore the fact that the United States possesses one of the two largest arsenals of nuclear weapons in the world.
A nuclear deterrent has been the bedrock of our national defense since World War II. And so long as other countries possess nuclear weapons that could be used against us, we too must maintain a safe, secure, and effective nuclear arsenal to deter attacks against ourselves and our allies.
That is why, early in the administration, we increased funding to maintain our arsenal and modernize our nuclear infrastructure—so that our arsenal remains safe and reliable—even with fewer weapons, and even without tests.
This investment was not only consistent with our nonproliferation goals—it was essential to them. Guaranteeing the capabilities of our stockpile allowed us to continue to pursue nuclear reductions without compromising our security.
And as part of President Obama's charge to reduce reliance on "launch under attack" procedures in U.S. planning, the Department of Defense has adjusted our planning and processes to give the president more flexibility in deciding how to respond to a range of nuclear scenarios.
In our 2010 Nuclear Posture Review—we made a commitment to create the conditions by which the sole purpose of nuclear weapons would be to deter others from launching a nuclear attack.
Accordingly, over the course of our Administration, we have steadily reduced the primacy nuclear weapons have held in our national security policies since World War II—while improving our ability to deter and defeat any adversaries—and reassure our Allies—without reliance on nuclear weapons.
Given our non-nuclear capabilities and the nature of today's threats—it's hard to envision a plausible scenario in which the first use of nuclear weapons by the United States would be necessary. Or make sense.
President Obama and I are confident we can deter—and defend ourselves and our Allies against—non-nuclear threats through other means.
The next administration will put forward its own policies.
But, seven years after the Nuclear Posture Review charge—the President and I strongly believe we have made enough progress that deterring—and if necessary, retaliating against—a nuclear attack should be the sole purpose of the U.S. nuclear arsenal.
If we want a world without nuclear weapons—the United States must take the initiative to lead us there. Moreover—as President Obama poignantly highlighted during his visit to Hiroshima—as the only nation to have used nuclear weapons, we bear a great moral responsibility to lead the charge.
That's why we negotiated with Russia the most ambitious arms reduction treaty in two decades—New START.
I fought hard for this treaty—as I have for every substantive arms control agreement since the 1970s—because it makes Americans safer.
It's not about trust or goodwill.
It's about strategic stability and greater transparency between the world's two great nuclear powers—a fact that has become more critical as our relationship with Russia has grown increasingly strained.
New START enshrines rigorous verification and monitoring mechanisms for nuclear reductions. And, next year—when the central limits of the treaty come into effect the strategic nuclear arsenals of our two countries will be at their lowest level in six decades.
That is a major step forward. But I confess, it is not as much progress as our administration hoped to make.
For the past three years, Russia has refused to negotiate additional reductions of deployed and non-deployed arsenals.
But American leadership on this issue need not wait for Russia.
Since 2009, the United States has dismantled 2,226 nuclear warheads.
And I'm proud to share some news.
After determining that we can safely reduce our nuclear stockpile even further—over the past year, President Obama set aside almost 500 warheads for dismantlement on top of those previously scheduled for retirement last year.
That puts our active nuclear stockpile at 4,018 warheads in service and approximately 2,800 in line to be destroyed. And we have recommended that the next administration conduct a comprehensive nuclear posture review to determine whether additional reductions may be undertaken.
As I have long said—the United States is strongest when we lead not only by the example of our power, but by the power of our example.
Our efforts have not only reduced the threat that nuclear weapons pose to our future, they have positioned our successors to continue making progress toward the day when we can finally and forever rid our world of this scourge.
But I am not here to only laud our successes.
We did not accomplish all that we hoped.
We lobbied hard for the U.S. to ratify the Comprehensive Test-Ban Treaty.
The United States has not conducted a nuclear test for more than two decades. The directors of our nuclear laboratories tell us that we know more about our arsenal today—and its reliability—through Stockpile Stewardship than they did when testing was commonplace. And ratifying the treaty would be an incredible boon to strengthen the existing global norm against nuclear testing—yet we were blocked at every turn in the Senate.
I did not always support the decisions made by President Reagan or either of the Presidents Bush—but during my 36 years as a Senator, I repeatedly helped improve and pass arms-control measures pursued by Republican presidents for one simple reason: nuclear security is too important for party politics—for our nation and the world.
And although we no longer live with the daily dread of nuclear confrontation, the dangers we face today also require a bipartisan spirit.
The challenges looming on the horizon will require leadership not only from the next President and Vice President, but from Congress as well.
While the vast majority of the international community understands that the world is more dangerous when more nations and people wield nuclear weapons, there are still those who seek to grow their arsenals and develop new types of nuclear weapons.
Not just North Korea, but Russia, Pakistan, and others have made counterproductive moves that only increase the risk that nuclear weapons could be used in a regional conflict in Europe, South Asia, or East Asia.
Working with Congress, the next administration will have to navigate these dangers and—I hope—continue leading the global consensus to reduce the role of nuclear weapons in our world.
In particular, they will have to determine how best to improve strategic stability with Russia—which has eroded over the past few years.
While we have shifted our security doctrine away from our nuclear arsenal, they have moved to rely more heavily on theirs.
Some of that has to do with Russia's concerns about the technological advances and superior conventional capacity of the United States military.
But it is a shift in strategy that increases the nuclear danger to our world.
Furthermore, Russia is currently in violation of the Intermediate-Range Nuclear Forces Treaty, which has been in effect for almost 30 years.
And they have thus far refused to engage constructively with the United States on returning to compliance or to broach discussions about strategic stability and future arms reductions.
As the next administration navigates these difficult security tasks—they will have to make decisions for America's security that recognize budgetary constraints and require tradeoffs.
If future budgets reverse the choices we have made—and pour additional money into a nuclear buildup that hearkens back to the Cold War—it will do nothing to increase the day-to-day security of the United States and our allies.
And it will mean we will have fewer resources to devote to areas that are indispensable to our 21st century security needs—areas like cybersecurity, space, and the health and modernization of our conventional force.
It risks placing the theoretical power of a weapon we hope-to-God never to use again above the tools our military uses each and every day.
It risks increasing the chances of a nuclear conflict through miscalculation—and destroying the confidence-building measures and security agreements that have protected the American people for decades.
And it risks degrading America's moral leadership in the world—diminishing our standing with our allies and compromising our capacity to achieve any of our other goals with the international community.
I know that as we move forward in this debate—there will be voices who counsel a nuclear arms race in the name of realism.
I know, because they have always been there.
And their arguments make even less sense now—in a world where the most challenging nuclear threat comes not from foreign governments with advanced technology—but from the terrorist with a crude Cold War relic in a suitcase, heading for any major city in the world.
In that first speech in Prague eight years ago, President Obama distilled the essence of the problem when he said: "Some argue that the spread of these weapons cannot be stopped, cannot be checked – that we are destined to live in a world where more nations and more people possess the ultimate tools of destruction. Such fatalism is a deadly adversary, for if we believe that the spread of nuclear weapons is inevitable, then in some way we are admitting to ourselves that the use of nuclear weapons is inevitable."
Over the past eight years, we have sought to defeat fatalism.
We have rejected inevitabilities.
As a nation, I believe we must keep pursuing the peace and security of a world without nuclear weapons—because that is the only surety we have against the nightmare scenario becoming reality.
This was a problem created by human ingenuity.
So it can be solved with human ingenuity and a belief in our better angels. Our capacity for destruction must always be balanced by the weight of shared responsibility.
That's a belief I have held for more than 40 years.
It's one I have fought to make real time and again.
And one I have been honored to keep advancing for the American people alongside President Obama for the past eight years.
May God continue to bless the United States of America.
And God protect our troops.