Our national defense establishment is at a critical inflection point. For 25 years after the end of the Cold War, the United States was able to operate as though the era of great power competition was over. That is clearly no longer the case. Now, America must face up to this reality.

As we adjust to the new era of great power competition, Washington must be clear-eyed about the cumulative effects of its national defense decisions and indecision over recent years. Persistent counter-terrorism operations have placed enormous burdens on our military. Misplaced priorities and acquisition failures have left the United States without critical defense capabilities to counter increasingly advanced near-peer competitors. Our political leaders have often added to this burden by providing insufficient and unstable defense funding. These and other challenges have produced military readiness and modernization crises that are harming each of our military services and putting the lives of America’s servicemembers at greater risk.

The bottom line is this: As a result of the decisions Washington has made — as well as those it has failed to make — America’s military advantage is eroding. This is particularly true when it comes to Russia and China. Both countries continue to rapidly modernize and expand their forces and present significant military challenges to the United States. Both powers could credibly threaten our security, prosperity, and way of life. And while the United States presently maintains an aggregate global military advantage over both countries, it is not unreasonable to assess that Russia or China could soon achieve a regional balance of power in their favor. As David Ochmanek of the RAND Corporation testified early this year to the Senate Armed Services Committee, “U.S. forces could, under plausible assumptions, lose the next war they are called upon to fight.”

The window of opportunity to restore and maintain the military advantage of the United States is still open, but it is rapidly closing. While I will continue to advocate for the larger defense budget that our military needs, the fact is that we cannot simply “buy our way out” of our current predicament. Larger budgets will not relieve us of the duty to prioritize and make difficult choices about the threats we face and the missions we assign to our military. That is what the next National Defense Strategy, due to Congress next month, must do. It represents the last realistic opportunity to develop an effective approach to confront growing threats in an era of renewed great power competition. America no longer has the luxury of waiting another four years to deal with these threats.

After a succession of defense strategy documents increasingly divorced from the strategic realities confronting the United States, Congress acted in the National Defense Authorization Act for Fiscal Year 2017 , which mandated that the National Defense Strategy be a classified document, not an unclassified one, as it was before. Similarly, Congress provided greater flexibility to encourage the secretary of defense to develop an impactful strategy that actually makes difficult choices to guide resource allocation and force development. Specifically, the National Defense Authorization Act requires the National Defense Strategy to address six key elements: the current and anticipated strategic environment, prioritization among threats and missions, the roles and missions of the armed forces, force planning constructs and scenarios, force posture and readiness, and anticipated major investments required to execute the strategy.

The Senate Armed Services Committee recently convened a hearing to receive recommendations from a distinguished panel of bipartisan defense experts on the development and implementation of the National Defense Strategy. A few consensus themes emerged.

Make Tough Choices

Above all else, the National Defense Strategy should make tough choices. Lt. Gen. Thomas W. Spoehr (U.S. Army, ret.) of the Heritage Foundation said at the hearing:

American defense strategies often fail by endeavoring to be completely inclusive of all parties and valuing their contributions equally…Some capabilities, organizations, and elements of infrastructure are not as important as others, and the [National Defense Strategy] should not pull back from identifying those that are less critical for success.

The success or failure of this strategy will ultimately be determined by its ability to set clear priorities about the threats we face and the missions we assign to the U.S. military. The global challenges facing the United States have never been greater. The strategic environment has not been this competitive since the Cold War. America no longer enjoys the wide margins of power it once had over its competitors and adversaries. The United States cannot do everything it wants everywhere. It must choose. It must prioritize.

This is why the next National Defense Strategy is so critical: It must tell the military and Congress how our nation should prioritize among a number of very different national security missions, often requiring the development of different kinds of capabilities, and how to devote finite taxpayer dollars wisely to accomplish these goals.

I am under no illusion about how difficult this will be. It will be impossible to please everyone with a National Defense Strategy that makes tough choices. Any attempt to do so will not only be foolishly in vain, but also jeopardize the quality of the strategy. That is why, as I have made clear before, as Secretary of Defense James Mattis and his civilian leadership team confront the difficult choices ahead — especially as they identify necessary tradeoffs — they will find allies in the Senate Armed Services Committee and its chairman.

Prioritize Great Power Competition

A strategy that does not prioritize among the threats confronting the United States will be useless. At the committee hearing, Mackenzie Eaglen of the American Enterprise Institute testified incisively:

Claiming the “five challenges” of China, Russia, Iran, North Korea, and persistent counterterrorism operations are all equally important is not strategy—it is the absence of one.

While the most dynamic and complex security environment in 70 years presents our nation with a multitude of threats, the challenges posed by Russia and China are unique in scale and scope.

Thomas Mahnken of the Center for Strategic and Budgetary Assessments warned:

[W]e find ourselves today once again in a period of great-power competition with an increasing possibility of great-power war. It is the most consequential threat that we face, and failure to deter and prepare adequately for it would have dire consequences for the United States, our allies, and the global order. Because of that, I believe that preparing for great-power competition and conflict should have the highest priority.

However, as Mara Karlin of the Johns Hopkins School of Advanced International Studies rightly pointed out, while “the Asia-Pacific and Europe are the priority theaters for the U.S. military…the United States cannot remain a global power if it dismisses other regions.” In the foreseeable future, the U.S. military will remain engaged in a long-term effort to counter the terrorist threat across much of the Middle East, Africa, and South and Southeast Asia. While America’s defense strategy and force development should prioritize great power competition and make informed decisions for managing risk in our other missions, it is clear the U.S. military also needs to be sized and shaped to address other ongoing regional threats and contingencies.

In light of other priorities and finite resources, it is imperative for the National Defense Strategy to provide guidance on how to prioritize among these many missions and sustain them over a long period of time in more cost-effective ways. At the same time, the strategy must ensure that the military we build has sufficient capacity and capability to maintain deterrence against North Korea and Iran, support U.S. allies, and be prepared to fight and win if deterrence fails, without compromising other priority missions.

Set Clear Priorities for Force Development

Of course, simply stating that the Department of Defense should prioritize the challenges presented by Russia and China is not enough. To be truly impactful, the National Defense Strategy must detail how the department will develop a force to achieve America’s national security interests in view of these challenges. In this sense, the strategy should not just be descriptive, but directive — providing clear focus and direction on force size and posture, readiness, and modernization.

Ochmanek emphasized this point before the Senate Armed Services Committee:

The two things that are needed now are money and focus—in particular, additional money to allow the Department to move swiftly to develop, acquire, and field new systems and postures and a focus on fielding capabilities that can make the greatest and most enduring contributions to a robust defensive posture vis-à-vis China, Russia, and other adversaries.

Many of these capabilities exist right now, as Ochmanek rightly stressed:

In short, we need not and should not wait for the maturation of exotic new technologies in the Third Offset or other long-term research and development initiatives before investing in things that can make major differences in the ability of U.S. forces to deter and defeat aggression by even the most capable adversaries.

A strategy focused on force development for great power competition would need to address priority mission sets, including offensive strike, defensive fires, sea control, air superiority, space, electronic warfare, cyber operations, and logistics in a contested environment. These are all areas in which Russia and China have made significant strides in the quantity and quality of their weapons.

In addition, a more sustainable approach to counter-terrorism and other military missions in largely permissive environments will require the rapid development and fielding of systems that our warfighters do not presently possess. For example, continuing to use F-18s, F-22s, and F-35s to prosecute low-end counter-terrorism missions is overkill and only consumes the readiness of these platforms. That is why the Senate Armed Services Committee has pushed the joint force to procure a light attack aircraft with capabilities specifically tailored for low-end missions. America needs other ideas and more capabilities along these same lines.

The National Defense Strategy should address the key capabilities that our joint force must have to maintain military overmatch against Russia and China and the priority investments necessary to develop these joint force capabilities.

Fully Integrate Allies and Partners

The National Defense Strategy should address how the United States can work more effectively with its allies and partners. As many of the witnesses reminded the Senate Armed Services Committee, America’s allies represent a significant long-term competitive advantage over China and Russia. And it would be both unwise and infeasible to take on the challenges of great power competition without them.

I believe there are important opportunities to improve our cooperation, planning, and alignment of capabilities with key allies in NATO and the Asia-Pacific region. While much attention has been paid of late to the levels of defense spending by our allies, which must increase, the National Defense Strategy should focus on identifying ways in which allies’ planned investments and those of the United States can be complementary and maximize interoperability and multiply the deterrent and defensive power of our alliances.

Into the Future

The United States has entered a renewed era of great power competition with its military advantage eroding—and eroding fast. The National Defense Strategy, backed by a strategy-driven defense budget, represents perhaps the last, best chance to restore that advantage and provide America’s military with what it needs to succeed. The Senate Armed Services Committee stands ready to do our part and provide timely, comprehensive, and effective resources and authorities to support the National Defense Strategy. I fear the consequences for our nation and the world if we fail to seize this opportunity. But I have confidence that if we do, we can restore American power and defend the international order that has produced and extended security, prosperity, and liberty across the globe.

Sen. John McCain (R-Ariz.) is the chairman of the Senate Armed Services Committee.

Image: Defense Department/Jette Carr