Correction: A previous version of this commentary miscalculated the number of operational F-35C squadrons with the U.S. Navy. The service has one.

On Jan. 1, Congress overrode then-President Donald Trump’s veto of the fiscal 2021 National Defense Authorization Act. Much of the news was about the vote itself, but another important story is the 93 F-35 fighter jets that were included in the bill — 14 more than the Pentagon requested in its budget.

Congress recognizes that the F-35 is the cornerstone of deterrence in the great power competition that we face as a country. The 2018 National Defense Strategy acknowledged that “inter-state strategic competition, not terrorism, is now the primary concern in U.S. national security. ... Long- term strategic competitions with China and Russia are the principal priorities for the [Defense] Department, and require both increased and sustained investment, because of the magnitude of the threats they pose to U.S. security and prosperity today, and the potential for those threats to increase in the future.”

One of the top three defense objectives is “deterring adversaries from aggression against our enemies.” The F-35 is the linchpin deterrent capability. Since the first two hours of Operation Desert Storm, we have enjoyed the luxury of maintaining air superiority, if not air supremacy. That will not be the case in any conflict with Russia or China. In fact, it would not even be the case in a conflict with Syria with the S-400 air defense capabilities.

It is easy to forget: there is no guarantee we will continue to enjoy the luxury of operating in a permissive environment as we have throughout the last 20 years. We should not forget the costs we endure without it. In Vietnam 2,561 fixed-wing aircraft were lost. In the most recent conflict with contested airspace, Operation Allied Force in Kosovo in 1999, the only aircraft permitted to fly deeply into Serbia were B-2s and F-117s supported by American EA-6B Prowlers and F-16CJ suppression-of-air-defense aircraft. I remember because I flew in that conflict, and I have vivid memories of the night an F-117 was shot down by Serbian air defenses.

Today, only 17 percent of the U.S. Air Force’s bomber and fighter inventory consists of stealth aircraft that are capable of maneuvering freely in contested areas created by modern surface-to-air and air-to-air threats. The Navy has only one operational F-35C squadron, and the Marine Corps has five operational F-35 squadrons (four which fly the F-35B and one which flies the F-35C). The Air Force has five operational F-35A squadrons. This is but a modest deterrent capability.

As Dr. Thomas Schelling noted in his seminal work, “Arms and Influence,” “the power to hurt is bargaining power. To exploit it is diplomacy, vicious diplomacy, but diplomacy.”

Deterrence relies on the credibility of your threat. Today we do not possess the robust capability that our adversaries know would be able to impose massive damage on the first day of a conflict and then generate sorties at a rate to continue that effort. We can make our threats sincerely, but without a capability to back them up, they’re not credible.

Beyond the need for stealth aircraft to operate in a contested environment, the services are struggling to maintain the readiness of an aging fleet of aircraft. A Government Accountability Office report published in November 2020 examined 46 different types of aircraft in the inventory and found that only three met their annual mission-capable goals in the majority of years from 2011 through 2019, and 24 did not meet their annual mission-capable goals in any fiscal year.

On top of these readiness challenges, we are still faced with a capacity shortfall. We have gone from an Air Force that in 1987 had 4,468 fighter aircraft and 331 bomber aircraft to one that has 1,481 fighter aircraft and 122 bomber aircraft. Part of the solution to that is the acquisition of the F-15EX, an advanced version of the F-15E. Current plans call for acquiring 144 aircraft at a cost of $87.7 million per jet. But that is an expensive Band-Aid, particularly when one must factor in that it actually sacrifices capability: The F-15EX cannot survive in an integrated, anti-access environment.

The challenge is to get enough F-35 shadows on the flight lines to have an operational capability that is a credible deterrent. Congress and the new administration should consider accelerating production, even if it means doing less in other areas of military spending — yes, including counterterrorism.

We must do more than pay lip service to the stated priority of restoring our competitive edge by blocking Russia and China from challenging us and our allies. In the 1980s, we stationed more than 350,000 American troops in Europe as a capable and effective deterrent. Fortunately, none of those troops saw combat. They didn’t because of Dr. Schelling’s point that “coercion depends more on the threat of what is yet to come than on damage already done.” We should invest and prepare for the threat of what is yet to come.

Scott Cooper is a retired U.S. Marine Corps officer who flew the EA-6B Prowler. He co-authored “No Fly Zones and International Security: Politics and Strategy.”

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