Nuclear weapons, in the wrong hands, threaten the very existence of the U.S. And, yes, some of the “wrong hands” have them.

This is why it’s absolutely critical that the Nuclear Posture Review (NPR), launched last week by the Defense Department, gets things right.

The review, a comprehensive reassessment of U.S. nuclear weapon policy and the capabilities needed to execute them will take months to complete. Done right, it will: guide the administration to strengthen U.S. nuclear deterrence, correct the Obama administration’s flawed nuclear weapon policies and assure more than 30 allies around the world that rely on extended deterrence from the U.S. for their national security.

U.S. nukes serve an important purpose: They encourage others to not build their own weapons, lessening the likelihood of a nuclear war. That’s no easy feat; just think of a certain dictator with a chubby finger on a nuclear button so close to our allies in South Korea or Japan. Both of these countries have the know-how and the resources to produce many nuclear weapons. They have chosen not to, largely due to U.S. guarantees.

The last NPR, produced in 2010, was misguided by wishful thinking about U.S.-Russian relations. It argued that Russia was no longer an adversary and that the potential for conflict was low. In reality, Russia had invaded Georgia just two years earlier, would invade Ukraine in 2013. It would also launch the most extensive nuclear weapon modernization since the end of the Cold War, even as Vladimir Putin further consolidated his power and restricted democratic movements within Russia itself.

Clearly, Russia sees the U.S. as an adversary, violates an alphabet soup of international agreements and regularly threatens European allies with preemptive nuclear strikes. To underscore the seriousness of its threats, Russia conducts military exercises that practice attacks — including the use of nuclear weapons — on our European allies.

The next NPR would be foolish to turn a blind eye to all of this. For example, it should recommend that the U.S. not extend the New Strategic Arms Reduction Treaty — set to expire in February 2021 — until Russia demonstrates it can be a trustworthy treaty partner.

Russia has repeatedly violated the Intermediate-Range Nuclear Force Treaty since 2008 in an effort to undermine the North Atlantic Treaty Organization politically and to intimidate its European members. A recommendation that the U.S. withdraw from this broken pact would certainly be in order, too.

Nuclear deterrence was no cakewalk during the Cold War and has become even more complex since. Before 1989, the U.S. not only developed a variety of nuclear weapon systems, it tested them regularly to ensure their safety, security, reliability and military effectiveness. That went by the wayside when the last NPR made it U.S. policy to not develop new nuclear weapons and not give the current stockpile new missions or capabilities. This policy should be overturned.

New actors might require new deterrence approaches and new capabilities. The primary goal is to prevent a large-scale attack on the U.S. If that will require new nuclear weapons or yield-producing experiments, the nation should not hesitate to pursue them. Others certainly don’t.

Both Russia and China reportedly conduct small-scale nuclear weapon experiments and work on advanced nuclear warhead designs. In contrast, the newest U.S. nuclear warheads were designed in 1980s; our last nuclear-weapon test occurred 25 years ago.

Our aging nuclear triad — bombers, land-based missiles, and strategic submarines — will have to be recapitalized in the next two decades.

These systems present a unique challenge to U.S. adversaries to decapitate the land-based missiles, an adversary has to attack U.S. territory directly indicating his intent. Strategic submarines are difficult to find. Bombers provide the president an unparalleled signaling ability.

These attributes will be as critical for our national security in the future as they have been so far.

The next NPR offers a great opportunity to put U.S. deterrence policy on a 21st century footing.