The August 18 test of an American missile previously banned by the INF Treaty, and the responses from Russia and China, have launched us headlong into a new era.

Vladimir Putin has vowed to match any U.S. missile deployments, while Russia and China have jointly complained to the UN Security Council, seeking to cast blame on the United States without mentioning their own growing deployments. Meanwhile, CSBA’s Timothy Walton and columnist Bret Stephens, both writing in the New York Times, have urged the deployment of previously banned INF missiles to counter the Russian and Chinese buildup of nuclear and conventional arms.

We don’t know where this will end. Policymakers must be clear-eyed as we move toward possible deployment of new missiles in Europe and Asia.

For decades, U.S. national security policy has been shaped by a combination of deterrence and arms control. Republican and Democratic administrations alike have placed high priority on ensuring we have a credible deterrent against any nuclear threats we face. We also have expended huge resources to make sure that our conventional forces can defend against any threats to the United States or its allies, and to protect U.S. interests around the globe. However, deterrence, especially nuclear deterrence, carries risks and dangers. Escalation of a conflict to nuclear war would have devastating consequences for the United States and the rest of the world.

Thus, arms control has been pursued to temper the dangers of nuclear weapons, to promote a safer world, and to help dampen political rivalries between major powers. Arms control has provided a measure of predictability in deployments through mutual limits and the exchange of information to make verification work. The INF Treaty went further than any other arms control agreement to achieve these goals. This is why the demise of the treaty — it officially died on Aug. 2 — has caused such great concern in many quarters, especially in Europe.

But arms control can work only when there is mutual compliance by the parties to an agreement. This has been the rub with the end of the INF Treaty. Vladimir Putin’s reckless deployment of the 9M729 cruise missile in violation of the agreement led to the unraveling of the treaty. This is regrettable because security in Europe and Asia is at greater risk than before, especially in Europe, where nuclear threats in the 1980s drove the effort that led to the INF Treaty. With the restraints under the treaty gone, the United States and Russia are free to deploy any previously INF-prohibited missiles they choose. In both Europe and Asia, there is the prospect of an open-ended arms race in missile deployments.

This is the direction in which Walton and Stephens both appear to point. Stephens seems to acknowledge the dangers by noting that without U.S. missile deployments, there will be no leverage to convince Russia, and even China, to apply the brakes on an arms race. He recalls that the deployment of U.S. Pershing and cruise missiles in Europe in 1983 played an essential role in achieving the INF Treaty. For the time being, both the U.S. and Russia have indicated an intention to deploy only conventionally armed missiles. Such missiles do not have the same frightening implications of nuclear weapons, but once deployed, they can always be rearmed with nuclear warheads.

Either way, though, there will be a backlash among publics who will not welcome the ratcheting up of nuclear or conventional dangers. NATO governments in Europe have already indicated they do not want to do a replay of the tribulations that allies went through in the 1980s to bolster NATO’s deterrent, even in light of the remarkable success of the INF Treaty. Our allies in Asia will also not be enthusiastic about placing U.S. ground-launched INF missiles on their territory, as statements by the South Korean and Australian governments recently indicated. It is hard to picture a different reaction in Japan.

Ultimately, the U.S. and its allies will do what has to be done to maintain a strong deterrent. Apart from ground-launched INF missiles, there are good ways to do this with air-launched and sea-launched missiles, which were not banned under the INF Treaty. It is difficult to see how Russia would conclude that an arms race with the U.S. will enhance its security, but we can’t be certain. Vladimir Putin’s attachment to nuclear weapons as an expression of Russian power can be traced to 1999 when he served as Boris Yeltsin’s national security advisor before being appointed as prime minister. His nuclear blustering today indicates that has not changed. China’s self-perception as a rising power that can challenge the United States will not make reaching arms control agreements easy or even plausible.

Still, as it has in the past, U.S. national security policy can seek to bolster deterrence with arms control agreements that reduce dangers and improve stability. Although there is concern that voices in the Trump administration would favor shifting the balance to sole reliance on deterrence, it is an open question today what direction the administration will take. The fate of the New START treaty on strategic arms remains to be settled. Emerging threats in space and cyber warfare present further challenges. President Trump has spoken about the need for 21st-century arms control. Apart from including China in the process and expanding the types of nuclear arms to be covered, it is not clear what such arms control would look like. U.S. and Russian officials began Strategic Stability Talks in July. Maybe a clearer picture will emerge.

At the end of the day, arms control cannot succeed unless mutual interests align, political conditions permit, and parties negotiate in good faith. Political leadership remains central to success in reducing nuclear and other dangers, as it did when the INF Treaty was negotiated. Leadership means having a clear set of objectives, marshalling talents in the government to carry out the sustained effort that is needed, and a steady hand throughout the process. Nothing is guaranteed, but Americans and our allies look to U.S. leadership not just to assure deterrence, but also to seek to reduce the dangers that arms competition inevitably create. Let’s hope the Trump administration will get on it.