“Our nuclear deterrent is nearing a crossroads. To date, we have preserved this deterrent by extending the lifespan of legacy nuclear forces and infrastructure—in many cases for decades beyond what was originally intended. But these systems will not remain viable indefinitely. In fact, we are now at a point where we must concurrently modernize the entire nuclear triad and the infrastructure that enables its effectiveness.”
General Paul Selva, USAF (Ret.), Former Vice Chairman of the Joint Chiefs of Staff
Nuclear deterrence is the bedrock of U.S. national security, serving as the backstop and foundation of U.S. national defense and the defense of U.S. allies since 1945. The U.S. nuclear deterrent is comprised of nuclear weapons and delivery systems, nuclear command, control, and communications, and the people and infrastructure that support it all. While U.S. nuclear weapons have not been employed since World War II, the United States uses its nuclear deterrent every day to maintain peace around the globe. The U.S. nuclear deterrent underwrites every U.S. military operation.
There have been three distinct eras since the dawn of the nuclear age in the United States. The first era began with the use of an atomic bomb in 1945, followed by a nuclear arms race with the Soviet Union, and ended with the last U.S. nuclear explosive test in 1992 after the end of the Cold War. The second era, from 1992–2018, was characterized by the sustainment of the Cold War legacy deterrent in the absence of underground nuclear testing. This era ended with the publication of the 2018 Nuclear Posture Review (NPR), which acknowledged the resurgence of Russia and the rise of China as strategic competitors and potential adversaries.
The United States is currently in the midst of transitioning to the third nuclear era, which will be characterized by limited nuclear weapons production without nuclear explosive testing. Once again the United States is doing something that has never been done before-in this case rebuilding its nuclear production capability after decades of inactivity and deferred recapitalization.
During the first nuclear era, the United States focused on developing and refining the military uses of nuclear energy, with increasing sophistication and technical acuity. At the beginning of the second nuclear era, there was hope that the fall of the Soviet Union would lead to global stability and security and, therefore, the United States endeavored to lead the world in reducing the role and number of nuclear weapons. Unfortunately, while the United States was focused on maintaining its existing nuclear systems, Russia and China were emphasizing the role of nuclear weapons in their military strategies and actively increasing the quantity and sophistication of their nuclear forces.
The 2018 NPR recognized this reality and ushered in a third nuclear era, acknowledging the return to Great Power competition and the enduring need for the U.S. nuclear deterrent to be effective in the face of an increasingly complex and dangerous strategic environment. The United States cannot project power against nuclear-armed adversaries without effective, reliable nuclear forces. Today, Russia is modernizing across its nuclear arsenal as well as its other strategic systems. The strategic calculation that once propelled U.S. nuclear strategy during the Cold War has been reversed, and Russia is now building up its nuclear capability in order to counter the perceived dominance of U.S. conventional forces. Additionally, Russia has adopted military strategies and capabilities that rely on nuclear escalation for their success. Russia has been developing, testing, and fielding new systems for its nuclear triad over the past decade. This includes new road-mobile and silo-based intercontinental ballistic missiles (ICBMs), ballistic missile submarines (SSBNs) and missiles, bomber aircraft, and cruise missiles. Russia is also actively testing never-before-seen nuclear capabilities such as hypersonic glide vehicles, nuclear-powered and nuclear-armed cruise missiles, and nuclear-powered unmanned underwater vehicles.
China, too, is modernizing and expanding its already considerable nuclear forces, marking the return to Great Power competition. China is developing, testing, and fielding new generations of land-based ballistic missiles, increasing the range of its submarine-launched ballistic missiles, and pursuing a new bomber. China is also expending significant resources on advanced nuclear-capable systems and hypersonic vehicles. See Figure 1.1 for an overview of the nuclear environment in which the United States is fielding a modern deterrent for the 21st Century.
Nuclear weapons came into being as a result of a bold attempt to invent a practical way to use an untested technology. The Manhattan Project delivered the world’s first atomic bombs in 1945. On July 16, 1945, the United States detonated its first nuclear explosive device, called “the gadget,” at the Trinity Site in New Mexico. Twenty-one days later, President Harry S. Truman authorized a specially equipped B-29 bomber named the Enola Gay (Figure 1.2) to drop a nuclear bomb, dubbed Little Boy (Figure 1.3), on Hiroshima, Japan. When the Japanese failed to surrender, a second B-29 bomber, Bockscar (Figure 1.4), dropped a second U.S. atomic weapon, Fat Man (Figure 1.5), on Nagasaki.
The use of nuclear weapons shortened the war and reduced the number of potential casualties on both sides by precluding a planned U.S. land invasion of Japan. The atomic bombs dropped on Hiroshima and Nagasaki remain the only nuclear weapons ever used in combat..
The United States did not remain the sole nuclear power for long. The Soviet Union tested its first nuclear device in August 1949. The United Kingdom became the third nuclear weapons state with its first test in October 1952.
The era that followed was defined by the competition between the two nuclear superpowers, the United States and the Soviet Union. New weapon designs were rolled out on a regular basis, and nuclear explosive testing supported continuous innovations in nuclear weapons technology.
At the beginning of the nuclear era, the U.S. nuclear weapons program focused on producing sufficient nuclear material to build enough weapons for a secondstrike capability-the ability to attack after absorbing an all-out first strike-as well as fielding weapons on almost every type of military delivery system available, including nuclear depth charges and nuclear artillery shells. By 1967, the United States had over 30,000 nuclear weapons in its arsenal. Many of these were “tactical”- shorter range, lower yield, non-strategicnuclear weapons. The United States relied on nuclear weapons as the only means available to counter the dominance of Soviet conventional forces, particularly in Europe.
After 1967, U.S. priorities shifted in the face of economic pressures. Because warheads were less expensive than missiles, U.S. strategy emphasized nuclear weapons with high yield-to-weight ratios and the ability to field Multiple Independently Targetable Reentry Vehicles (MIRVs), allowing several warheads to be mounted on a single missile. This required a shift in the production focus from quantity to sophistication. Modernization programs for many U.S. weapons systems featured improved operations and logistics for the military operator, more modern safety, security, and control features, and better military performance characteristics (e.g., selectable yields and greater accuracy). The United States also drastically reduced its stockpile of non-strategic nuclear weapons. These changes were made possible by a better understanding of nuclear physics and weapon designs provided by nuclear explosive testing.
At the end of the Cold War, with the dissolution of the Soviet Union, there was reduced focus on nuclear weapons without a nuclear superpower rival. With the near simultaneous end of both nuclear weapons production in 1991 and nuclear testing in 1992, the new challenge facing the nuclear enterprise was to maintain and sustain the legacy deterrent without production or testing, and to extend the operational lives of both weapons and delivery systems indefinitely.
In 1991, the United States closed the Rocky Flats plant in Colorado, which had produced up to 1,500 plutonium pits a year for the stockpile. The same year, in an effort to realize the “peace dividend” from the end of the Cold War, President George H.W. Bush ordered the withdrawal and destruction of ground-launched short-range missiles that had carried nuclear weapons, and the removal of all tactical nuclear weapons from surface ships, attack submarines, and naval aircraft. In 1992, in anticipation of a potential comprehensive test ban treaty, the United States voluntarily suspended its program of underground nuclear testing, and has not conducted an explosive nuclear test since.
The abrupt termination of both nuclear weapons production and testing brought an immediate halt to the continuous cycle of modernization programs that included building and subsequently replacing the weapons in the stockpile with newer, more modern designs. A key part of this process was the use of nuclear testing to refine new designs in the development process, to test the yields of weapons after they were fielded, and to define and repair certain types of technical problems. Without an ability to produce new weapons or to test, the United States was faced with the unexpected challenge of sustaining the deterrent in a new and unknown way. It was a time of great uncertainty as well as creativity as new paths were forged.
The National Defense Authorization Act for Fiscal Year 1994 directed the Department of Energy (DOE) to establish a Stockpile Stewardship Program (SSP) as a substitute for underground nuclear testing, using science-based methods and advanced computing to guarantee that the stockpile remained safe, 6 Nuclear Matters Handbook 2020 secure, and effective without the need to conduct nuclear explosive tests. At the time, no one knew exactly how this was going to be accomplished.
Since 1994, DOE, and subsequently the National Nuclear Security Administration (NNSA), have successfully maintained and sustained the safety, security, and effectiveness of the stockpile without nuclear explosive testing. Through the development of new scientific, computational, and technical tools and methodologies, the Secretaries of Defense and Energy have been able to certify the continued viability of the U.S. nuclear deterrent without nuclear explosive testing every year since 1995.
The United States has not produced a new nuclear weapon (with new nuclear components) since 1991. During this time, the United States also significantly reduced its stockpile quantities. In 1991, the U.S. nuclear stockpile had 19,000 nuclear weapons; by 2003, there were approximately 10,000; by 2009, there were roughly 5,000. In 2017, the last time the United States published unclassified stockpile numbers, there was a total of about 3,800 weapons. Figure 1.6 shows the size of the U.S. nuclear stockpile from 1945 to 2017.1
Because the United States has produced no new nuclear weapons, it has instead extended the lives of the weapons in the legacy stockpile. Life extension programs (LEPs) have underpinned the ability of the United States to sustain its weapons well beyond their original design lives. Until these legacy weapons are replaced with newly manufactured weapons, which is currently planned to begin in the early 2030s, these weapons will continue to age.
The U.S. nuclear stockpile has continued to decrease in quantity in accordance with arms control treaties with Russia and internal U.S. decisions concerning the appropriate size of the U.S. nuclear deterrent. The New START Treaty, which limits the number of strategic weapons for the United States and Russia, will expire on February 25, 2021. There is an option to extend the treaty for a period of no more than five years if both parties agree.
The 2018 NPR recognized that a new era for U.S. nuclear policy has begun. The world is more dangerous than the United States had hoped. Nuclear competition among Great Powers has not gone away. While the NNSA SSP has succeeded in keeping the legacy stockpile safe, secure, and effective up to this point, it cannot continue to do so indefinitely. The United States will once again be faced with the challenge of doing something it has never done before: reconstituting a nuclear weapons production capability without the benefit of nuclear explosive testing. At the same time, the threat is evolving and becoming increasingly complex, including potential cyber threats and threats against the U.S. industrial base and the supporting supply chain. The United States is embarking on the largest, most complex nuclear modernization effort in its history. As illustrated in Figure 1.7, it will be 45 years between the peak of the last modernization effort in 1984 and the next peak, projected for 2029.
The United States is modernizing all three legs of its nuclear triad, and is also reconstituting its weapons production capability at roughly the same time. The average age of U.S. nuclear weapons will be more than 40 years old at life extension or planned retirement-more than twice their original design lives. All life-extended weapons in the stockpile will reach the end of their planned lifetimes by mid-century, which in some cases is more than three times as long as they were designed to operate. Some components of those life-extended weapons (e.g., plutonium pits) have been reused as-is, meaning that those components have been in the stockpile for many decades beyond their originally projected lifespans, and will remain in the stockpile until they can be replaced.
U.S. nuclear delivery systems are similarly situated, with all of them being sustained beyond their design lives. By 2035, 100% of U.S. nuclear delivery systems will have exceeded their design lives by an average of 30 years. By the early 2040s, 100% of U.S. nuclear delivery vehicles will have reached end of life. At retirement, both the air-launched cruise missile (ALCM) and the Minuteman III ICBM will be over 50 years into their 10-year design life. The Ohio-class SSBN is already beyond its projected lifetime, and the B-2A bomber and the F-15E dual-capable aircraft will both be approaching 40 years old before they are retired. The B-52 bomber will be about 100 years old when it is finally scheduled to retire in the mid-2050s.
All current U.S. ballistic missile warheads were designed and built in the 1970s and 1980s, and their designs addressed specific Cold War problems from the 1960s. In the time of high stockpile numbers, U.S. nuclear tactics emphasized overwhelming adversary defenses using many weapons to defeat a single target and using as much yield as possible given space and weight constraints.
For deterrence purposes, the current composition of the stockpile must contain the attributes required to maintain sufficient diversity and flexibility, to include:
Nuclear deterrence is the number one priority mission of DoD and its highest investment priority. DoD expects nuclear modernization, including strategic delivery platforms and nuclear command and control systems, to cost approximately 3.7% of the DoD budget during the peak of the 23-year modernization period (this does not include the costs for NNSA). Total projected costs for sustainment plus modernization of U.S. nuclear forces is approximately 6.4% of the DoD budget in the same time period (see Figure 1.8). By these measures, these efforts are notably more cost effective than in the past-the previous two large nuclear recapitalization efforts required 10.6% of the defense budget in the early 1980s and 17.1% of the defense budget in the early 1960s. As former Secretary of Defense James Mattis affirmed, “America can afford survival.”
While some may characterize the past three decades as the United States doing nothing while U.S. adversaries continued to advance their offensive and defensive forces, the United States has not been idle. The U.S. military has operated the nuclear force so that the deterrent has done its job, as evidenced by the fact that no nuclear weapons have been employed in combat since 1945. In addition, U.S. scientists, engineers, designers, and production workers have maintained the stockpile and successfully extended the lives of U.S. weapons without the need to resume nuclear explosive testing.
However, Cold War legacy delivery systems and their associated weapons cannot be sustained indefinitely. It is necessary to modernize the nuclear deterrent to avoid “rusting to zero” (performance degradation due to weapons aging). A modern U.S. deterrent must also be threat responsive, and able to take advantage of technological advances, as adversary technologies also advance. Replacement programs are underway to ensure there are no capability gaps when these legacy systems age out, or become obsolete due to advances in adversary capabilities.
Nuclear deterrence will continue to be vital to U.S. national security strategy and be underpinned by nuclear forces and effective nuclear command, control, and communications. The nuclear deterrent will provide survivable, responsive capabilities to ensure adversaries do not attempt a disarming first strike; demonstrate resolve through the positioning of forces, messaging, and flexible response options; ensure the United States can respond to a broad range of contingencies with tailored options; and mitigate the risk of a technological failure or adversary breakthrough while providing adaptability to changes in the security environment.
1 The number of warheads depicted in Figure 1.6 include both active and inactive warheads. Several thousand additional nuclear warheads are retired and awaiting dismantlement.
2 U.S. Department of Defense, “Nuclear Posture Review,” (Arlington, VA: U.S. Department of Defense, February 2018), 43–44, website link here