The use of U.S. nuclear forces to protect the territory of its allies, commonly known as extended deterrence, has been an essential pillar of U.S. strategy in Northeast Asia since the early decades of the Cold War. The longstanding justification for maintaining extended deterrence is that doing so both prevents adversaries from mounting attacks on allies and dissuades allies from seeking their own nuclear weapons. As in the past, the United States relies on nuclear weapons to make extended deterrence credible. However, given that extended deterrence relying on nuclear weapons is becoming increasingly risky, the U.S. should consider how conventional forces can contribute to extended deterrence.
Effective extended deterrence requires careful consideration of U.S. strategic goals in Northeast Asia. Developments in the region will put pressure on U.S. President Joseph Biden and his administration to strengthen extended deterrence to allies. Still, an approach that sets unachievable expectations and misinterprets the drivers of nuclear escalation could inflame arms races and damage strategic stability.
Walking the tightrope of effective extended deterrence will require the Biden administration to think carefully about how conventional military strategies can generate or attenuate the danger of nuclear escalation. As Northeast Asian states, friend and foe alike, rapidly improve their military firepower, the goal of preventing nuclear attack will increasingly depend on how states plan and posture for conventional war.
The most important, though not only, objective of U.S. extended deterrence is to prevent nuclear attack against allies. During the Cold War, nuclear danger was very high because both the United States and Soviet Union adopted damage limitation strategies. As a result, conventional forces could not be discounted entirely from the extended deterrence equation, but their ability to prevent nuclear use or control escalation was limited.
Modern Northeast Asia has different sources of nuclear escalation, and therefore requires a different approach to extended deterrence. Moreover, the drivers of nuclear instability in the region have more to do with conventional warfighting strategies than the nuclear balance between the United States and its adversaries. Therefore, any effort to strengthen extended deterrence and improve strategic stability should place greater emphasis on changes to conventional strategy rather than adjustments to U.S. nuclear forces or doctrine.
The primary source of nuclear risk in the U.S.-China relationship is inadvertent escalation resulting from conventional attacks that degrade Beijing’s confidence in its secure, retaliatory nuclear forces.1The seminal work on inadvertent escalation is: Barry Posen, Inadvertent Escalation: Conventional War and Nuclear Risks (Ithaca: Cornell University Press, 1991), which examined the concept in the US-Soviet late Cold War scenario. For a more recent examination of escalation in Northeast Asia — a US-China conflict over Taiwan, to be precise — see: Caitlin Talmadge, “Would China Go Nuclear? Assessing the Risk of Chinese Nuclear Escalation in a Conventional War with the United States,” International Security 41, no. 4 (Spring 2017): 50-92, https://doi.org/10.1162/ISEC_a_00274. Conventional operations targeting Chinese dual-capable missiles, strategic surveillance capabilities, and command and control networks are especially worrisome. Destruction of these targets would give the United States and its allies the best chance of prevailing in a conflict, but such capabilities are also important for maintaining a secure second strike. Washington might be able to reduce this escalation risk by adopting alternative strategies for conventional deterrence that emphasize greater survivability of U.S. forward-deployed forces and eschewing early attacks against sensitive Chinese targets.
North Korea has a different route to nuclear escalation than China, but it is still heavily influenced by conventional considerations. The Democratic People’s Republic of Korea (DPRK) would most likely use nuclear weapons first in an attempt to preempt a looming attack by the United States. This is a very precarious nuclear strategy, but given North Korea’s much weaker conventional forces, it has few viable options to deter U.S. conventional strikes besides going nuclear as quickly as possible.2The latest official North Korean statement on nuclear use scenarios can be found in a January 2021 report on the Eighth People’s Congress of the Workers’ Party of Korea, which contained the following sentence: “[The report] reaffirmed that the DPRK, as a responsible nuclear weapons state, will not misuse its nuclear weapons unless the aggressive hostile forces try to have recourse to [sic] their nuclear weapons against us.” See: “Great Programme for Struggle Leading Korean-style Socialist Construction to Fresh Victory On Report Made by Supreme Leader Kim Jong Un at Eighth Congress of WPK,” Rodong Sinmun, January 10, 2021. While the United States can adjust its conventional strategy vis-à-vis China to address nuclear risk, such an approach is unlikely to work with North Korea given the latter’s geography and smaller, more vulnerable nuclear arsenal.
Another complicating factor for U.S. extended deterrence in modern Northeast Asia is the region’s burgeoning missile arms race that places stronger precision strike systems in its allies’ hands. Multiple allies are pursuing long-range, conventional strike capabilities that could allow them to go after sensitive targets in China and North Korea. For example, South Korea has clearly signaled that it intends to use its Hyunmoo cruise and ballistic missiles to decapitate North Korean leadership to protect itself from nuclear attack.
Capable allies are a double-edged sword for U.S. extended deterrence. On the one hand, stronger allies are in a better position to contribute to their own defense and bolster conventional deterrence. But, on the other hand, Washington may not be able to constrain how allies employ their more advanced capabilities in a crisis or conflict.
In addition to considering the relationships between conventional strategies and nuclear escalation, the Biden administration should set more reasonable goals and expectations than its predecessor. American nuclear forces can help reassure allies, but in modern Northeast Asia, their utility for both deterring clashes and preventing nuclear escalation within conflict is limited.
Therefore, if the Biden administration wishes to strengthen extended deterrence in Northeast Asia, it must consider how the United States approaches the challenge of deterring conventional crises or attacks because nuclear risk stems from conventional conflict. For example, greater attention on hardening, dispersal, and survivability will reduce the advantages that adversaries gain by targeting fixed locations. In addition, using U.S. forces to blunt offensive actions and disrupt air and naval power projection would carry a lower likelihood for escalation than conducting quick, deep strikes.
Admittedly, such a conventional strategy could be applied to a U.S.-China scenario but not a North Korea scenario. There is little that U.S. extended deterrence can do to reduce nuclear danger vis-à-vis North Korea; it can either keep risk stable or increase it if the United States adopts aggressive posturing a la 2017. If the Biden administration wants to improve the prospect of nuclear stability with North Korea, it will have to do so through creative diplomacy.
Extended deterrence in Northeast Asia will become a more salient issue as the new Biden administration doubles down on great power competition with China and sets higher barriers to nuclear diplomacy with North Korea. The previous administration tried to address extended deterrence challenges by adding more types of nuclear weapons and generally increasing the prominence of nuclear forces for U.S. foreign policy, but this approach misinterprets the sources of nuclear risk in modern Northeast Asia. Thus, as the Biden administration crafts its nuclear and defense strategies, it should seriously consider how conventional weapons and strategies to employ them affect nuclear escalation.
Eric Gomez is the Director of defense policy studies at the Cato Institute.