Much of the attention around President-elect Joe Biden’s nomination of retired Gen. Lloyd Austin as secretary of defense has focused on civilian control of the military and the necessary congressional waiver for his confirmation.

However, that is perhaps not the biggest challenge he’ll face, if confirmed.

The tenure of the next defense secretary will begin with an enormous challenge: building a military capable of meeting threats from great powers like China and Russia, as well as spoilers like Iran and North Korea. The nation’s defense strategy and defense budget are the building blocks to do so.

Austin has no record to speak of on defense budget debates. Although this is unsurprising for a military officer who spent his career relying on civilian officials to address questions of policy and politics, it is unusual for a secretary of defense nominee — one consequence of nominating a recently retired military officer to lead the Pentagon.

Even before the economic downturn triggered by COVID-19, calls to reduce defense spending emerged from the wings of both parties. Now, with historic deficits following federal spending on COVID-19 relief, those calls are increasing in frequency and intensity.

Although defense cuts may sound like an easy way to alleviate pressure on the budget, the new administration and Congress must be mindful of the consequences of such a move. Given the stakes, it’s worth taking a deeper look.

To examine the real consequences of cuts to the Pentagon’s resources, the Ronald Reagan Institute and the Center for Strategic and Budgetary Assessments hosted two Strategic Choices Exercises this fall. Bipartisan groups of recognized leaders in their fields — defense and budget experts, current and former policy makers, and industry executives — utilized CSBA’s interactive Strategic Choices Tool to weigh the tangible implications of defense budget changes.

Participants examined two different, 10-year budgetary scenarios: the 3 percent real growth that previous Pentagon leaders determined is required to execute the current national defense strategy, and the 10 percent cut proposed by some political leaders over the summer, including the House Progressive Caucus, Sen. Bernie Sanders, I-Vt., and incoming Senate Majority Leader Chuck Schumer, D-N.Y.

The results of this bipartisan group effort were clear: defense budget cuts would have devastating consequences of our military and our national security. A 10 percent cut would leave the United States with a military that is incapable of carrying out the current National Defense Strategy. It would compel the Department of Defense to re-examine its current standard of maintaining a force that can win one war while deterring another.

Severe cuts to force structure — the size and organization of our military — made all teams question America’s ability to win one war, let alone deter another. In other words, the United States could be reduced to a de facto hemispheric power by 2030.

Although participants tried hard to avoid significant cuts to military end strength and strategically divest from outdated or duplicative platforms, it was simply impossible to achieve the necessary cost-savings for a 10 percent cut without eviscerating force structure. The Army took the brunt of the cuts, reducing its forward presence and diminishing its ability to conduct the kind of large-scale, protracted operations potential conflict might require.

The consequences are even worse as you look deeper into the scenario’s specifics. Cuts to force structure, modernization, and personnel would result in additional stress on a military that already has a severe readiness problem. Without a parallel reduction in the frequency of military operations, increased strain on forces and equipment that could result in more tragic accidents like the collision of the destroyer Fitzgerald that killed seven sailors in April 2019.

On the strategic level, the consequences are no less real. Defense cuts would place further strain on an alliance system already under pressure. They would leave the United States with less forward presence to deter adventurism by adversaries and assure allies that America will come to their defense.

The incoming Biden foreign policy team has already made a commitment to revitalizing America’s alliances. But friendlier rhetoric alone will not persuade our partners that the United States is a reliable ally. Sufficient investment in defense capabilities is the clearest indicator to foreign leaders that Washington will stand by its friends. Cuts to our defense budget communicate the opposite message to allies, partners, and competitors.

We hope leaders in the next administration and the new Congress are paying attention. The results of our Strategic Choices Exercises paint a picture of a world none of us want to see — but one that may not be far off if calls to slash the defense budget aren’t challenged. Policymakers have only to ask themselves if they want to be faced with the unacceptable consequences outlined here, or if they’re prepared to advocate for the resources the military needs.

Thomas G. Mahnken is president and CEO of the Center for Strategic and Budgetary Assessments. Roger I. Zakheim is Washington director of the Ronald Reagan Presidential Foundation and Institute.