Reassuring allies is a never-ending assignment. That task is especially challenging in Northeast Asia, where the usual problems created by geography and different geopolitical interests are compounded by an evolving security environment characterized by North Korea’s continued progress in developing long-range missiles and nuclear weapons, China’s steady military modernization and more assertive regional role, growing diffusion of the nature and source of threats (notably due to the rising prominence of the cyber and space domains), and political dysfunction in Washington that makes it more difficult for allies to anticipate America’s reaction to a crisis.

Fortunately, the United States understands the critical importance of honoring its alliance commitments and defending its allies. Failure to do so would spell the end of those security partnerships, which provide Washington with immense benefits. The chief difficulty is not assuring allies that the U.S. commitment to their defense is strong, but reconciling allied expectations of U.S. action with what Washington can and will do.

What, then, should allies expect from Washington? U.S. allies should expect high-level public support from the U.S. government in the form of authoritative statements by the president and secretaries of state and defense, and they should expect those commitments to be regularly affirmed in the documents issued at “2+2 meetings.” Both Japan and South Korea can point to such statements: the Japanese have U.S. President Obama’s affirmation during his April 2014 visit that the Senkaku islands are covered by the U.S.-Japan Mutual Cooperation and Security Treaty and the South Koreans have the 2009 joint declaration by Obama and then President Lee Myung-bak that explicitly cited the importance of the extended deterrent to that partnership.

Complementing the work of the highest level of government is day-to-day engagement by a professional and responsive bureaucracy that is experienced and shares the priorities and sensitivities of its ally. That describes the vast majority of individuals working these security partnerships. Even political appointees understand the issues and recognize the value of U.S. alliances.

Our Asian allies should also expect genuine dialogues with the United States on core alliance issues, venues that since their establishment have allowed them to share views and get insight into U.S. policy. Both Japan—in the Extended Deterrence Dialogue, or EDD—and South Korea—in the Extended Deterrence Policy Committee, or EDPC—have regular bilateral meetings with U.S. counterparts to address extended deterrence issues. These track-one discussions are supplemented by a number of unofficial dialogues, some of which the CSIS Pacific Forum runs, to further explore issues and probe still further—and more candidly—differences between each country and their respective roles and responsibilities.

Reassurance is further strengthened by the continuing modernization of alliances. Military capability and readiness is enhanced by new hardware, new doctrines, and joint exercises. A seamless integration of forces is the strongest signal that the United States and its ally are united and that an attack on one is an attack on both. A forward military presence is a core element of U.S. reassurance and it will continue, even if it may diminish in specific locales. Allies should expect the movement and rotation of troops, which they should see as a way of boosting readiness, not reducing a commitment.

Finally, allies should expect new forms of political, diplomatic, and economic engagement to strengthen the ties that bind them to the United States. This is the rationale behind the U.S. “rebalance”: it aims to forge multifaceted connections to Japan, South Korea, and East Asia as a whole to enhance the U.S. commitment to the most dynamic region of the world. Too often overlooked or considered as a secondary dimension by Tokyo and Seoul, non-military U.S. engagement is a critical piece of the reassurance puzzle because it plays a significant role in further coupling the United States with its allies.

There are forms of reassurance that allies should not expect from the United States, however, and they should adjust their expectations accordingly. First, allies should not expect U.S. protection to be a silver bullet, nor should they expect Washington to use force to respond to every incident that occurs. As President Obama put it in his commencement address at West Point last year, “Just because we have the best hammer does not mean that every problem is a nail.” The United States commitment to Tokyo and Seoul, of course, is solid and Washington (along with the U.S. Pacific Command, U.S. Forces Japan, and U.S. Forces Korea) will make sure that the United States military will defend them when needed. But the United States may in some instances honor its commitments without using force and, increasingly, it will look to Tokyo and Seoul to take up their share of the defense and deterrence burden, especially to deal with contingencies at the lower end of the escalation ladder.

Allies should realize that the use of force need not be automatic and understand that the call for greater allied participation and contributions is not a form of disengagement or abandonment but, rather, a way to consolidate relations and strengthen partnerships. Deterrence is best accomplished when the United States and its allies present a seamless front—when they are so tightly integrated that adversaries cannot see daylight between the two countries. Moreover, when Tokyo and Seoul do more for their own defense (and that of the United States) and when they further integrate their forces with Washington, it will also be more difficult for the United States to fail to honor a commitment. Put simply, the more responsible the ally, the more the United States will be bound to it. From a U.S. perspective, improved trilateral cooperation among Washington, Tokyo, and Seoul would also be a welcome addition to the bilateral tracks because managing escalation in a regional contingency would likely involve all three allies. The United States understands the political challenges of such trilateral coordination given the poor state of Japan-South Korea relations, but is willing to take a step-by-step approach to advance cooperation; the Pacific Forum CSIS’s track-1.5 U.S.-Japan-South Korea Extended Deterrence Dialogue is making headway in this area. Tokyo and Seoul, in other words, should expect more calls for burden-sharing with Washington and among each other, developments that they should welcome because it will strengthen their security. The conclusion last December of a trilateral information-sharing agreement, which allows Tokyo and Seoul to voluntarily exchange intelligence on North Korea’s nuclear and missile programs with each other through the United States, is a “good first step,” as David Shear, U.S. Assistant Secretary of Defense for Asian and Pacific Security Affairs, recently put it.

Second, allies should not expect too much from nuclear weapons. Although the 2010 US Nuclear Posture Review makes clear that security architectures in Northeast Asia (and other key regions) will retain a nuclear dimension so long as nuclear threats remain, the United States has set out a comprehensive approach that relies on nuclear and non-nuclear means, namely missile defense and conventional strike systems. Tokyo and Seoul should understand that this shift, which started during the previous administration of George W. Bush, is meant to strengthen, not weaken, deterrence. While there are threats that need to be addressed with nuclear means, others do not. After all, the threat of U.S. nuclear-use may not always be credible. An adversary may believe, rightly or wrongly, that there are forms of aggression that fall beneath the U.S. nuclear response threshold. Greater reliance on non-nuclear means helps solve this problem. Incidentally, non-nuclear means also offer important deterrence benefits. Missile defense of the U.S. homeland and deployed forces, for instance, further couples the United States with its allies, mitigating if not eliminating an adversary’s option to create a wedge between them.

In this spirit, allies should not expect redeployment of U.S. nuclear weapons in Northeast Asia. South Koreans, in particular, have frequently requested that Washington redeploy tactical systems to the Peninsula to help deter North Korea from provocative actions. This call misses the point that nuclear weapons do not play a useful role to deter such actions and, significantly, that such a move would be politically counterproductive as various governments work to denuclearize the Peninsula. The development of indigenous nuclear weapons by allies, sometimes called for by South Koreans and to a far lesser extent Japanese, would be equally counterproductive and would likely kill the alliances because the United States has vested interests in upholding nonproliferation rules and norms.

American nuclear weapons, of course, will retain a vital role in the extended-deterrence equation and Tokyo and Seoul should expect to be involved in discussions of nuclear policy and doctrine with Washington. But allies are not going to get the transparency and granularity that they seek. Tokyo and Seoul often ask for a detailed picture of a U.S. nuclear response in particular contingencies and scenarios; what the United States would target, which weapon systems it would use, and how those weapons would be deployed. These are unrealistic requests. The United States does not share that information with any ally. The belief that this somehow constitutes the core of discussions in the North Atlantic Treaty Organization’s Nuclear Planning Group is mistaken.