Nuclear Weapon Sole Purpose: The Strongest Future for U.S. National Security and Global Stability

By the Hon Andrew Weber and Rear Admiral John Gower

Concept #1: Nuclear Weapon Sole Purpose: Days before President Trump was sworn in, retired Vice President and now President-Elect Joe Biden Jr, gave a speech at the Carnegie Endowment for International Peace.[1]  In it he summarized the progress of the so-called “Prague Agenda” that was set out in the famous speech in that city by President Obama in 2009 and codified in the 2010 Nuclear Posture Review (NPR).  In that speech he referred to an ambition, echoed in the 2010 NPR, to create the conditions for a sole purpose nuclear doctrine:

Given our non-nuclear capacities 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 would 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.” 

That ambition was one of many thwarted by the countervailing balances of power throughout most of the Obama presidency, and the Trump administration has taken US nuclear policy in a starkly different direction.

Almost exactly three years later, Biden repeated his commitment to this objective in a comprehensive tour of his foreign policy goals as a putative presidential candidate published in Foreign Affairs on 23 January of last year[2]:

“… I will take other steps to demonstrate our commitment to reducing the role of nuclear weapons.  As I said in 2017, I believe that the sole purpose of the U.S. nuclear arsenal should be deterring—and, if necessary, retaliating against—a nuclear attack. As president, I will work to put that belief into practice, in consultation with the U.S. military and U.S. allies.”

This blog summarizes a longer paper on the subject which will later be published through the Council on Strategic Risks.  Without underestimating the challenges facing a Biden administration in making changes to US policy, the search for a genuine change in nuclear postures has been strengthened by the victory of the Biden campaign in November.

Why Are We Not There Already?

Given that the impact of nuclear weapons stands so far removed and several orders of magnitude larger than any other means of inflicting damage and pain on an adversary, one could be forgiven for surprise that Sole Purpose was not already the default position of nuclear armed states.  For many reasons, some historical and some born of a differing viewpoint, current nuclear doctrine and architecture is portrayed by 4 of the 5 recognised NWS as essentially “almost sole purpose but with caveats.”[3]  These caveats are paraded as necessary either to provide “choice” in a crisis, to deliver “ambiguity” which by its advocates is portrayed as an enduring positive necessity, or by allowing for nuclear responses to non-nuclear threats, to broaden the scope of weapon use.  The latter of these also prevents any adoption of a no first use policy for nuclear weapons.

The effect of these caveats and the associated history has allowed the perpetuation and proliferation of nuclear capabilities and doctrines which weaken or threaten nuclear strategic stability. Adopting a Sole Purpose policy would show the United States beginning to pivot in a more stable and responsible direction.

Benefits of Sole Purpose

It would be naïve to underestimate the challenges of persuading both the US nuclear community and some allies that removing US nuclear capability as potential responses to a range of non-nuclear threats would generate benefit.  Notwithstanding these challenges, it is important to understand what significant shifts in US nuclear doctrine and declaratory policy would be enabled by the adoption of Sole Purpose, and what benefits they could bring to the nuclear world order, global strategic stability, and US and allied national security. 

Sole Purpose, a more restrictive doctrine where US nuclear weapons, and their associated doctrine and posture, exist only to deter against coercion or attack by other nuclear weapons would bring positive outcomes in three critical areas:

  • Sole Purpose would strengthen deterrence both by minimising the risk of miscalculation or misinterpretation and raising the threshold of first use of nuclear weapons.
  • Sole Purpose would strengthen US national security by allowing the reallocation of significant sums of money, currently earmarked for the current administration’s expansion of the scale and scope of the nuclear arsenal, properly to countering novel non-nuclear threats by non-nuclear means.
  • Sole Purpose would strengthen the NPT by giving the strongest signalsince 2010 of the veracity of the US commitment to its disarmament obligations, and a clear lead to other nuclear weapon states.

Strengthening Deterrence. The most pressing risk to nuclear (and wider) strategic stability is an escalation to a breach of the nuclear taboo through miscalculation or misinterpretation. This risk is multiplied and magnified by the number and variety of deployed systems, especially when operating behind a complex and often deliberately opaque veil of declaratory ambiguity. The most dangerous and destabilizing of such systems in the current and planned U.S. arsenal are the Air Launched Cruise Missile (ALCM), its planned successor the Long Range Standoff Weapon (LRSO), and President Trump’s revived Sea Launched Cruise Missile (SLCM) program.  These nuclear capabilities effectively lower the threshold of nuclear use and reduce the stabilising and necessary role of strategic nuclear deterrence. Because they are commonly used as conventional weapons, a country on the receiving end of one would likely not even know if it were carrying a nuclear weapon. Sole purpose would remove the raison d’etre of these more destabilising systems, and allow both declaratory and actual ambiguities to be cast aside.  Sole Purpose does not rule out strategic pre-emption in the face of an imminent major nuclear threat.

Strengthening US and Allied National Security.  A more stable and strategically-focused nuclear policy would allow the cancellation of proposed new capabilities or the decommissioning of existing less-than-strategic nuclear capabilities. These would be primarily those which most exacerbated the risk of miscalculation or misinterpretation as discussed above. Apart from the inherent value to US National Security of the resultant reduction in risk, funds released from the cancellation of new projects would allow greater investment in countering nuclear threats by novel non-nuclear means.

The justification often given for nuclear armed cruise missiles is that they can be used in regional conflicts in so-called limited nuclear war fighting scenarios, and this reassures our allies in Europe and East Asia.  Our nuclear umbrella would be much stronger, however, without these ambiguous nuclear weapons.  Indeed, our allies are not comforted by the prospect of “limited nuclear wars” being fought on or adjacent to their territory.  

Strengthening the NPT.  A declaration of Sole Purpose would defibrillate the failing heart of the NPT. It would give the strongest signal that once more, the US wanted to lead genuine progress in the Treaty’s ambition. It would lend significant weight to the US-led CEND process and reignite the almost extinguished faith that the largest democracy in the P5 was genuinely seeking to make good the promises in the Treaty itself and the removal of new nuclear weapons and systems would increase the likelihood that the US could ratify the CTBT. 


Adoption of Sole Purpose would clear a doctrinal path for focused arms control and reduction aimed at first restricting and then removing those capabilities which most threaten strategic stability. Such a doctrine would enable needed and stabilizing changes to the current U.S. nuclear force posture.  The adoption of Sole Purpose by a new US administration once more focused on global leadership would serve to strengthen deterrence, reassurance of allies, and reduce the risks of nuclear war.

[1] Remarks by the Vice President on Nuclear Security, Washington, DC, 11 Jan 2017

[2] Why America Must Lead Again: Rescuing U.S. Foreign Policy After Trump, Joseph R. Biden, Jr., Foreign Affairs, 23 Jan 2020

[3] NWS Negative Security Assurances near universally give exemption caveats to the strength of the assurance and the level of “extreme circumstances” in which nuclear weapon release would be contemplated.


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