New CSIS Report Analyzes Extended Deterrence and Assurance

By John K. Warden

Last month, the CSIS Defense and National Security Group, led by Clark Murdock and Jessica Yeats, released a new report dedicated exclusively to extended deterrence and assurance.  The report, entitled "Exploring the Nuclear Posture Implications of Extended Deterrence and Assurance," aims to identify the characteristics of the U.S. nuclear force posture that support extended deterrence and generate a strategy for maintaining assurance going forward.  The report begins by exploring extended deterrence and assurance at the conceptual level and then more specifically analyzes the competing needs and interests of U.S. allies in Europe, Northeast Asia and the Middle East.

Throughout the report, differences between extended deterrence and assurance are indentified.  For example, the difference between how allies and adversaries follow U.S. capabilities:

In contrast to potential adversaries who follow U.S. nuclear posture issues closely and with considerable expertise, U.S. allies’ defense planners may rely on less credible intelligence sources…and have more limited analytic resources for assessing the deterrence effects from changes in force structure…This explains why assurance requirements, at least in the near-term, can exceed the requirements of deterring the ally’s potential aggressor…allies can be more sensitive to certain force structure attributes and less sensitive (than their potential aggressor) to others. For example, ‘symbols’ of deterrence can be important to the credibility of assurance even if they do not affect an adversary’s deterrence calculations.

While the immediate requirement of assurance often exceed extended deterrence (the so-called 'alliance premium'), long-term trends are also more important to allies.  Murdock and Yeats write that:

because the choice to remain non-nuclear is based on the ally’s assessment of their security needs in a longer-term context, perceived challenges to the credibility of U.S. deterrence capabilities in the long-term could have shorter-term consequences for assurance.

Therefore, long-term trends such as the deterioration of America's arsenal or build-ups in China's arsenal can have profound effects on whether an ally like Japan feels assured.

The differences between extended deterrence are also important for each region.  Europe demonstrates that certain capabilities that have little importance for deterrence can still be important for assurance.  The report argues that:

U.S. strategic forces provide deterrence and extended deterrence (by affecting potential adversary calculations) while the forward-deployed U.S. NSNF provide a ‘coupling’ link between U.S. strategic forces and the security of its European allies, thereby contributing significantly to assurance.

This leads to the conclusion that:

U.S. forward deployed NSNF should remain in Europe as long as allies want them, and any removal decisions should be made only in close consultation with allies.

The differences between extended deterrence and assurance are also apparent in Northeast Asia.  For Japan, a long-term challenge by China is more important than other short-term threats (e.g. North Korea):

China dominates Japan's long-term defense planning. This is not because Japan fears an attack but because current military and economic trends point towards the eventual emergence of a regional environment within which China can "effectively [impose] its will within the region...at seemingly low thresholds."97 Japan is highly sensitive to the long-term implications of these trends…China’s strategic modernization is particularly troubling to Japan because “despite the big gap, [the United States and China] are moving in opposite direction, and it is the relative change in the nuclear balance that is impacting Japanese policy makers.”99

However, Japan is still concerned with short-term symbols of assurance.  One issue, in particular, that has been grabbing headlines is the government of Japan's desire for the United States to retain the Tomahawk Land Attack Missile/Nuclear (TLAM/N).  Although not currently deployed, TLAM/N is seen by many in the Japanese bureaucracy as a symbol of America's commitment to Japan's security.  The report helps explain why Japan is attached to TLAM/N and how the Unites States might maintain assurance without it:

While Japan seems to attach importance to TLAM/N, the United States, with intensive consultations, should be able to explain to Japan that TLAM/N is not critical to the credibility of U.S. extended deterrence vis-à-vis Japan’s potential aggressors. According to Bunn, the Japanese interest in TLAM/N may be due to another case of ‘leading the witness’ during the 1994 NPR. In light of the decision to remove nuclear weapons from surface ships, “some US officials noted that the US retained the capability to redeploy TLAM-N on [attack submarines, which] may be source of some Japanese officials thinking TLAM-N is ‘their’ extended deterrent.” But by the same logic, “we may be able to shape how Japan thinks about TLAM/N” in today’s environment. Elaine Bunn argues that “with proper consultations” Japan can be assured “through other means” without TLAM/N. However, because of the attention and sustained effort that this would call for, “there have not been sufficient consultations to make this change in the near-term.”

While recognizing that each assurance relationship is distinct, the report comes to similar conclusions regarding Europe and Japan.  The requirements of assurance exceed extended deterrence, which may require the United States to keep capabilities such as non-strategic nuclear weapons in Europe or TLAM/N for Japan.  However, it's possible to close the gap.  With sustained consultations and alternate commitments, the United States might demonstrate its resolve and commitment while phasing out unnecessary capabilities.