The Biden administration last week published three documents that lay out core elements of its defense strategy.

They, along with the National Security Strategy (NSS) released earlier in the month, provide the framework for U.S. national security policy. Central to them all is deterrence, a beguiling and periodically bewildering concept that, while always important, has assumed greater significance at a time of growing geopolitical instability. It has also become much more difficult to practice as challenges multiply and the U.S. enlists more allies in that effort.

U.S. law mandates that an incoming administration publish a national security strategy within a year of taking office. The Biden report was delayed by events in Ukraine. The NSS frames other reports: the National Defense Strategy, the Nuclear Posture Review (NPR) and the Missile Defense Policy Review. Those three were completed months ago and summaries and fact sheets have circulated since the spring. Declassified versions were held back until the NSS was ready; its publication in early October allowed their release.

Multiple themes run through the four documents. The first is the priority attached to the Indo-Pacific region. It comes first in each strategy and all insist that it retains that status despite crisis in other regions.

Second, China is the top concern. The NSS “recognizes that (China) represents America’s most consequential challenge.” Secretary of Defense Lloyd Austin calls it the “pacing” challenge. That declaration, coming after seven months of conflict in Ukraine, is intended to signal that war in Europe has not upended the Biden administration’s priorities. (See point one.)

Third, alliances and partnerships remain the coin of the realm. The U.S. must work with partners to ensure stability and order.

Fourth, in this world, nuclear weapons remain not only relevant but necessary. Nuclear-armed adversaries are expanding and modernizing their forces. The U.S. must follow suit. As a result, the NPR retained longstanding language that “the fundamental role” of nuclear weapons is deterring an attack, leaving open the possibility that, in some circumstances, the U.S. might strike first with nuclear arms.

This is a rejection of the “sole purpose doctrine,” which argues instead that “the sole purpose” of nuclear arms should be to deter and, if necessary, to retaliate against a nuclear strike. That policy would preclude nuclear first use and Biden backed it during the 2020 campaign. Despite writing that “as president, I will work to put that belief into practice,” the protests of allies and the changing situation in Europe changed his mind.

Deterrence is tough. Despite decades of theorizing and strategizing, it remains a delicate balancing act that depends on perceptions more than realities and as such is inherently ephemeral. Effective deterrence requires not only that an adversary believe that it will suffer consequences for actions — crediting both capabilities and resolve — but it must also believe that such dangers are contingent or the product of its own actions.

Meanwhile, nations sheltering under Washington’s extended deterrent must agree with the U.S. assessment of both sufficient capabilities and credible commitments, despite very different geographical and geopolitical positions. They must believe that they will be defended even though threats are more palpable to them than the partner who courts risks on their behalf. That confidence must be retained even as the U.S. tries to find an acceptable equilibrium with the adversary. That is one of the biggest challenges when the U.S. tries to discuss “strategic stability” with China: allies fear that this undermines their defense.

Throughout it all, allies must not be emboldened to rewrite the status quo. That “sweet spot” — threatening enough to deter an actor but not so much as to make it fear the status quo, maintaining the confidence of an ally as confidence is built with the adversary — is a tiny piece of conceptual real estate.

So, for example, in a 2014 meeting, some Japanese participants expressed dismay that then-U.S. President Barack Obama hadn’t followed up his threat to retaliate after Syria used chemical weapons in its civil war — crossing a reputed “red line” — undermining U.S. credibility. Americans countered by noting that doing so would have ensnared the U.S. in another Middle East conflict when Asian allies were already complaining about distractions posed by involvement in Iraq and Afghanistan. Damned if you do, damned if you don’t.

Now, multiply the difficulty of that task by including more allies, each of which has its own adversaries, different and sometimes divergent views of the same adversary and whose perceptions and responses depend on the particulars of a crisis. That is a challenge in normal times. In a world of multiple conflicts, difficulties inherent in deterrence and reassurance expand exponentially.

The structure of U.S. of alliances in Asia contributed to the complexity of the assignment. Traditionally, U.S. conversations with those allies have been bilateral, an outgrowth of the “hub-and-spoke” model of U.S. security engagement with the region. For a variety of reasons, Washington preferred to segregate those discussions. That approach is now outdated.

One of the most important programs I worked on at Pacific Forum explored U.S., Japanese and South Korean reactions to a nuclear crisis in Northeast Asia. The project’s value reflected both the topic’s significance — dealing with the threat or use of nuclear weapons by Pyongyang or Beijing — and its sensitivity, which prevented the three governments from doing it on an official level.

It was a fascinating exercise. There were disagreements on fundamental questions between the U.S. and its allies as well as among the allies, with coalitions shifting depending on details of the crisis. Even as Tokyo and Seoul shared views of the North Korean government and agreed on the best way to deter its provocations, each government’s preferred U.S. response in a crisis depended very much of who has been attacked and how. Finding common ground when dealing with China was even harder.

Discussion of a Northeast Asian crisis must now include Australia, which is more deeply engaged by virtue of increasingly close defense ties with Japan, as well as membership in the Australia-U.K.-U.S. arrangement. That explains the NPR’s call for multilateral dialogue with Japan, South Korea and Australia “emphasizing a cooperative approach between the U.S. and allies and decision-making related to nuclear deterrence policy strategic messaging and activities that reinforce collective regional security.” The U.S. plans to build on existing dialogues with each partner to “identify pragmatic steps to enhance consultation,” such as “meeting at higher levels of seniority and examining options to improve crisis management consultation.”

The NPR reports that a focus of this effort will be improving information flows between the allies. That’s good, but not enough: Attention must also be paid to how the countries work together to better deter adversaries, a process that should build confidence among allies about the U.S. commitment to their defense.

The importance of allies’ roles is enhanced by the NPR’s declaration that the U.S. is focused on “the ability of nonnuclear capabilities to contribute to deterrence and will integrate these capabilities into operational plans as appropriate.” In other words (as I argued a few weeks ago), Washington can deter and defend without nuclear weapons, a policy that highlights the potential contributions of those partners.

Brad Roberts, a former Department of Defense official who drafted the NPR in the Obama administration, sees this as “beginning the process of creating a new division of deterrence labor among the U.S. and its allies (globally),” adding that “they won’t be reassured by the emerging problem; but they can be reassured that we understand the problem, have a plan to address it and see them as integral to the success of that plan.”

He warned that allies “will require some new capabilities and, more importantly, a political willingness to step out of current comfort zones and take on some new responsibilities.”

Elbridge Colby, another former Department of Defense official who drafted the last National Defense Strategy, elaborated: While the U.S. needs to reassure allies that it is prepared to meet their concerns, “that needs to be combined with serious pressure and a sense that our reassurance is not without limit. Allies genuinely need to pull their weight. This, he said, "is more like a private business partnership — where there is affinity and loyalty but an expectation of performance — than a family.”

Expanding those dialogues won’t be easy no matter how much sense the idea makes. Each partnership has a different comfort level, with a corresponding ease or reluctance to share information in front of others. Classification levels differ — the U.S. and Australia are members of the Five Eyes intelligence sharing group; Japan and South Korea are not — along with the integration and operability of forces. And, ignorance can be an asset, affording deniability to politicians and the public.

As always, the exercise boils down to trust in and the credibility of the U.S. commitment to the protection of its allies’ interests. Today, however, allies are more able to shape U.S. thinking but they must step up significantly to do so.

Brad Glosserman is deputy director of and visiting professor at the Center for Rule-Making Strategies at Tama University as well as senior adviser (nonresident) at Pacific Forum. He is the author of “Peak Japan: The End of Great Ambitions” (Georgetown University Press, 2019).