PONI Debates the Issues Blog

The triad of nuclear weapon delivery systems – consisting of land-based intercontinental ballistic missiles (ICBMs), strategic bombers, and nuclear-armed submarines – is the holy trinity of the U.S. nuclear arsenal. However, all three legs of the triad are aging and will need large-scale, expensive modernization in the coming decades if they are to be maintained. This has prompted a discussion about the continued necessity of the nuclear triad in the post-Cold War era. Is maintaining the triad worth the money? Or would the U.S. be better served by a different configuration of nuclear forces?

The threat environment that the United States faces today is radically different from that of the Cold War. The possibility of a massive “bolt from the blue” attack, which the triad was designed to prevent, is no longer a realistic concern. The budgetary environment has also changed dramatically. Defense budgets are declining, creating a situation of competing priorities between nuclear and conventional forces. Meanwhile, we are swiftly approaching what has been termed the “modernization mountain”: a period of very high planned expenditures in the late 2020s, when all three legs of the triad will come up for modernization at once. These modernization plans include a new SSBN(X) ballistic missile submarine, a new nuclear-capable long-range strike bomber, and a possible follow-on the Minuteman-III ICBM, among others. Over the next thirty years, maintaining the arsenal and pursuing these modernization projects is projected to cost the United States $1 trillion total.

To put it quite simply, this is unsustainable. The Navy has already admitted that it cannot afford the SSBN(X) and top Air Force leaders have recently made similar statements. Even though our nuclear forces make up only 3-5% of the defense budget, the money still must come from somewhere. The truth is that the United States is unlikely to get through the modernization mountain without making significant cuts to its nuclear forces. In light of that reality, the most prudent nuclear force configuration is perhaps not a triad at all, but a dyad. Since the super-survivable submarine leg will unquestionably be retained, this leaves the United States with two good options: a bomber/SSBN dyad or an ICBM/SSBN dyad.

Dyad 1: Bomber/SSBN

Cutting the ICBM leg in favor of a bomber/SSBN dyad is attractive primarily because the advantages offered by the ICBM leg are the ones that are least relevant in the post-Cold War era. The ICBMs can be launched quickly and their existence complicates enemy targeting significantly; however, these advantages are most useful in the case of an overwhelming “bolt from the blue” attack by a near-peer competitor. Today, the likelihood of such a massive attack without warning is widely acknowledged to be next to nil. States with the capability to carry out such an attack have no incentives to do so, and actors that would like to carry out such an attack do not possess the necessary capability. Furthermore, the perpetrator of such an attack would still face significant retaliation from our deployed nuclear submarines, which would remain intact.

Rather than a “bolt from the blue attack,” the more realistic scenario today is that of a gradually escalating crisis, in which tensions and nuclear threats ratchet up over time. A bomber/SSBN dyad would be perfectly suited to confront that possibility because the United States would have ample time to put its forces on high alert. In a time of crisis, we could deploy additional submarines for a total ten or twelve roaming the ocean at any given time, guaranteeing a robust second strike capability. Even if submarine detection technology improves significantly in coming years and the survivability of the SSBNs comes into question, it is highly unlikely that any adversary could simultaneously strike all of the Unites States’ non-deployed bombers and submarines as well as ten or twelve deployed submarines scattered across the world’s oceans.


The second dyad option, an ICBM/SSBN dyad, is a more nontraditional choice. As Tom Nichols recently argued, retaining the ICBM leg is valuable because it prevents the lowering of the nuclear threshold and makes any potential nuclear attack extremely costly for the aggressor. Any attack against the ICBM leg would represent a direct attack on U.S. territory; therefore, the ICBMs deny prospective enemies “any hope of half-way measures against us: if they mean nuclear war, then they must decide upon nuclear war.” As Nichols argues, the consequences of any exchange of nuclear weapons would be devastating to the United States and to the world no matter how small or limited the exchange. The prospect of massive retaliation from an ICBM/SSBN dyad would make this reality painfully obvious, lest any potential attacker believe that a limited use of nuclear weapons could be acceptable.

In this dyad, the SSBN leg would be maintained to enhance survivability whereas the bomber leg would be cut both in order to save money and as a way of tying our own hands. By denying ourselves the flexibility and wide range of options offered by strategic bombers, the United States would bolster the credibility of our massive retaliation pledge. The only advantage that would potentially be lost is political signaling: during a crisis, bombers can be sent on increased missions to demonstrate resolve or recalled to demonstrate a willingness to negotiate. However, the United States would still maintain other ways to demonstrate resolve, such as the deployment of increased SSBNs.

Smart national security

Dyad opponents argue that the ICBM leg is the cheapest of the three and that it doesn’t cost that much extra to make the new long-range strike bomber nuclear-capable. But in an era of declining budgets, it seems that the onus of proof should be upon those who wish to keep capabilities to prove that they are valuable, rather than on those who wish to make cuts to prove that they are not. After all, a few things that are individually cheap – if tens of billions of dollars can be considered cheap – can add up to quite a lot of money in total, as anyone who has ever managed their own personal finances knows.

At the end of the day either of these dyad options would preserve our nuclear deterrent, protect the United States, and maintain our extended deterrent pledge, all at a reduced cost. As an added bonus, moving to a dyad might even strengthen U.S. credibility on the world stage in terms of our commitment to nonproliferation and eventual nuclear disarmament. It’s not every day that we have the opportunity to make good national security policy while also saving money and pursuing one of our long-term international goals. Let’s make the smart choice now. If we don’t, unfortunate budgetary realities may force us to make even harder decisions later.  

Liz Whitfield is a research intern with the Project on Nuclear Issues. The views expressed above are her own and do not necessarily reflect those of the Center for Strategic and International Studies or the Project on Nuclear Issues.

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  • I would argue that getting rid of the bomber leg does impact our extended deterrence because of their ability to forward deploy around the world.  While this isn't necessarily as common for the B-2, the B-52 is quite often around the world conducting joint and coalition missions, even if just for training.  Even without a specific nuclear posture/increased readiness which would trend toward a nuclear conflict, the BUFF still projects nuclear power.  That show-of-force demonstrates to allies and adversaries that the US can reach out and touch any target in the world, either with conventional or nuclear weapons.  I perceive that as a fairly significant psychological impact of maintaining a bomber leg--key to the extended deterrence concept. 

  • Thanks for your comment! It's great to get some feedback on the post.

    My argument was more that states with the ability to conduct massive attacks have no incentive to do so for political reasons more than out of fear of our ICBM leg. Even aside from the danger of second-strike retaliation, it's difficult in the post-Cold War era to envision any state with the ability to conduct such a massive bolt-out-of-the-blue attack (namely, Russia) thinking that its national security incentives would be best served by bombing the the United States out of existence. Even with the current atmosphere of increasing tensions between Russia and the U.S., I have a hard time imagining that changing any time in the future. For one thing, such a massive nuclear attack would have catastrophic consequences for the world as a whole, not just the United States (ex. nuclear winter). 

    Your first point about the bomber leg gets to the heart of a debate that's far from resolved - whether a policy of massive retaliation is credible in response to a low-level nuclear attack. It's true that this could encourage an adversary to engage in lower level attacks if they doubt the credibility of our pledge, but it could also prevent them from engaging in any kind of nuclear attack in the first place as long as we can make our massive retaliation promise sufficiently credible. In terms of our nuclear umbrella, I don't see how getting rid of the bomber leg would effectively dismantle our extended deterrence commitment, given that we'd maintain two other perfectly sufficient delivery platforms.

  • These commonly proposed force structures fail to consider the purpose for each leg of the triad.  With regards to the ICBM, the states that have the capability to conduct massive attacks have no incentive BECAUSE of the ICBM leg.  That is one of the many reasons the ICBM leg is widely acknowledged as the stabilizing leg of the triad.  Eliminating the bomber has two critical negative consequences.  First, the President is stripped of options to control escalation.  Assuming an all-or-nothing nuclear posture may actually ENCOURAGE an adversary to engage in lower level nuclear attacks first, knowing that we have no credible response.  Furthermore, this would effectively dismantle the nuclear umbrella we use to assure our allies who, as a result, would likely seek their own capabilities to deter nuclear neighbors.

    I do not believe that our nation is willing to give up what the triad provides... even a part of it.  Sadly, something else will pay the price for modernization but the risk is too high not to keep all three legs of the triad.

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The views expressed above are the author’s and do not necessarily reflect those of the Center for Strategic and International Studies or the Project on Nuclear Issues. The content of this web site does not constitute an endorsement by or opinion of the Department of Defense or any sponsor of the Project on Nuclear Issues.