By Elbridge Colby

A quarter century ago, nuclear weapons were central to US military planning – yet today they are largely consigned to the background.  How important will they be a quarter century from now?

Many argue that the salience of nuclear weapons in military planning will continue to decline.  These observers point to the international opprobrium that constrains the employment or brandishing of such weapons, typified by the apparent growth of a “taboo” or “tradition of non-use,” as well as the more practical difficulties of using nuclear weapons in a rational and controlled fashion.  To these observers, assuming some degree of prudent statesmanship and good faith among the major powers, nuclear weapons will continue to recede in relevance.  Nuclear forces may well exist in the 2030s, but they will provide a basically existential deterrent, hardly impinging on the real world concerns of statesmen and military planners except as hazardous material to be properly accounted for.

But is this prediction of continuity correct?  Are nuclear weapons likely to be as marginal to US defense planning in the 2030s as they appear to be today?  There seem to be two primary reasons for doubt.

The first reason for doubt is the possibility of nuclear proliferation among smaller and medium powers.  From the Persian Gulf War through Iraq and Libya, the United States could and regularly did fight militarily unlimited wars against “rogue states.”  While the United States exhibited admirable restraint towards civilians in these conflicts, it neither needed to nor did recognize any fundamental necessity for restraint in its conduct of the war against its adversary; rather, it pursued regime change and total victory.  US forces could conduct their campaigns of “shock and awe” without serious consideration for the enemy’s capability to escalate in response.

But the conditions that allowed this are changing.  Countries ranging from North Korea to Pakistan have learned by observing the US way of war against Iraq and Libya that, as an Indian general pithily remarked about what to learn from the First Gulf War, it is foolish to fight the Americans without nuclear weapons.  If more countries acquire nuclear weapons – and especially survivable nuclear weapons – the United States will have to face the reality that adversaries might have the ability to launch nuclear attacks against its allies or even the United States itself even (and especially) if US forces initiate a full-scale attack.  This does not mean that the United States would need to forswear fighting nuclear-armed adversaries – but it would mean that the United States would need to learn – or relearn – how to fight limited wars, wars that seek to achieve US objectives while minimizing the probability that an adversary would escalate.

The second reason why nuclear weapons will probably be more salient is the likelihood of greater symmetry in the conventional military balance in theaters of prime interest to the United States.  While this is likely to be a longer-term development, the narrowing of US advantages in conventional warfare is likely to prompt US planners to think more about nuclear weapons as a way of shoring up its deterrent and defense postures by the 2030s.

The decline in the salience of nuclear weapons in the 1990s and early 2000s was a function of two events: the collapse of the Soviet Union and the maturation for the United States of the Revolution in Military Affairs (RMA).  The combination of these events propelled the United States to a position of olympian conventional superiority over any plausible foe in any plausible contingency.  But the strategic landscape has been changing.  A number of countries, above all China, are dedicating substantial resources to ambitious conventional military modernization programs.  And the RMA is spreading.  Countries such as China, Iran, India, Pakistan, and even non-state actors like Hezbollah are now exploiting the possibilities of advanced conventional weaponry, even as they also explore forms of “hybrid” warfare designed to undercut American military advantages.

The upshot of these developments is that the United States is likely to face a considerably more capable set of militaries than it did in the 1990s and 2000s, especially in the Pacific and the greater Middle East. US forces will have to strike deeper, harder, and more quickly against a wider range of adversary targets – and thereby take on greater escalatory risk – in order to accomplish military objectives against these opponents.  This reality will force American planners to consider the possibility that such conflicts could lead to escalation to the nuclear level with those states that possess such weapons.

Moreover, even with effective investments in cutting edge military technologies, by the 2030s the United States may face situations in which it finds itself at a conventional military disadvantage in regions of great importance to Washington, particularly the Western Pacific.  Depending on the trajectory of American investment in force modernization, US forces may, for instance, be inferior in the local balance of power or US power projection capabilities may rely on fragile, vulnerable, and readily disrupted or disabled assets. If the United States cannot achieve its regional military objectives with conventional forces, it will need to consider greater reliance on its nuclear forces to compensate for its conventional inferiority and/or vulnerabilities – if it wishes to maintain the network of extended deterrent guarantees that have undergirded global order since World War II.

The combination of these two trends suggests that nuclear weapons will play a more salient role in global politics by the 2030s than they have in the last two decades.

Elbridge Colby is a principal analyst and division lead for global strategic affairs at CNA.  He previously served in various positions with the US Government, where he focused on nuclear weapons policy and proliferation.