The Department of Defense has begun to ratchet up spending to recapitalize the U.S. strategic nuclear triad and its supporting infrastructure, as several programs move from research and development into the procurement phase. The projected Pentagon expenditures are at least $167 billion from 2021-2025. This amount does not include the large nuclear warhead sustainment and modernization costs funded by the Department of Energy, projected to cost $81 billion over the next five years.

Nuclear forces require modernization, but that will entail opportunity costs.In a budget environment that offers little prospect of greater defense spending, especially in the COVID19 era, more money for nuclear forces will mean less funding for conventional capabilities.

That has potentially negative consequences for the security of the United States and its allies. While nuclear forces provide day-to-day deterrence, the Pentagon leadership spends most of its time thinking about how to employ conventional forces to manage security challenges around the world. The renewed focus on great power competition further elevates the importance of conventional forces. It is important to get the balance between nuclear and conventional forces right, particularly as the most likely path to use of nuclear arms would be an escalation of a conventional conflict. Having robust conventional forces to prevail in or deter a conventional conflict in the first place could avert a nuclear crisis or worse.

For the foreseeable future, the United States will continue to rely on nuclear deterrence for its security and that of its allies (whether we should be comfortable with that prospect is another question).Many U.S. nuclear weapons systems are aging, and replacing them will cost money, lots of money.The Pentagons five-year plan for its nuclear weapons programs proposes $29 billion in fiscal year 2021, rising to $38 billion in fiscal year 2025, as programs move from research and development to procurement.The plan envisages a total of $167 billion over five years.And that total may be understated; weapons costs increase not just as they move to the procurement phase, but as cost overruns and other issues drive the costs up compared to earlier projections.

The Pentagon knew that the procurement bow wave of nuclear weapons spending would hit in the 2020s and that funding it would pose a challenge.In October 2015, the principal deputy undersecretary of defense said Were looking at that big bow wave and wondering how the heck were going to pay for it and probably thanking our stars that we wont be here to have to answer the question.

The Pentagons funding request for fiscal year 2021 includes $4.4 billion for the new Columbia-class ballistic missile submarine that will replace Ohio-class submarines, which will begin to be retired at the end of the decade; $1.2 billion for the life extension program for the Trident II submarine-launched ballistic missile (SLBM); $1.5 billion for the Ground Based Strategic Deterrent, an intercontinental ballistic missile (ICBM) to replace the Minuteman III ICBM; $2.8 billion for the B-21 stealth bomber that will replace the B-1 and B-2 bombers; $500 million for the Long-Range Standoff Missile that will arm B-52 and B-21 bombers; and $7 billion for nuclear command, control and communications systems.

The Pentagon funds primarily go to delivery and command and control systems for nuclear weapons.The National Nuclear Security Administration at the Department of Energy bears the costs of the warheads themselves. It seeks $15.6 billion for five nuclear warhead life-extension and other infrastructure programs in fiscal year 2021, the first year of a five-year plan totaling $81 billion.The fiscal year 2021 request is nearly $3 billion more than the agency had earlier planned to ask, which suggests these programs are encountering significant cost growth.

Some look at these figures and the overall defense budget (the Pentagon wants a total of $740 billion for fiscal year 2021) and calculate that the cost of building and operating U.S. nuclear forces will amount to only 6-7 percent of the defense budget.That may be true, but how relevant is that figure?

By one estimate, the cost of building and operating the F-35 fighter program for the U.S. Air Force, U.S. Navy and U.S. Marines over the programs lifetime will be $1 trillion.Amortized over 50 years, that amounts to $20 billion per year or only 2.7 percent of the Defense Departments fiscal year 2021 budget request.The problem is that these percentages and lots of other small percentages add up.When one includes all of the programs, plus personnel and readiness costs as well as everything else that the Pentagon wants, the percentages will total to more than 100 percent of the figure that Congress is prepared to appropriate for defense.

The defense budget is unlikely to grow.Opportunity costs represent the things the Pentagon has to give up or forgo in order to fund its nuclear weapons programs.The military services gave an indication of these costs with their unfunded priorities lists, which this year total $18 billion.These show what the services would like to buy if they had additional funds, and that includes a lot of conventional weapons.

The Air Force, for example, would like to procure an additional twelve F-35 fighters as well as fund advance procurement for an additional twelve F-35s in fiscal year 2022. It would also like to buy three more tanker aircraft than budgeted.

The Army is reorienting from counter-insurgency operations in places such as Afghanistan and Iraq to facing off against major peer competitors, that is, Russia and China.Its wish list includes more long-range precision fires (artillery and short-range surface-to-surface missiles), a new combat vehicle, helicopters and more air and missile defense systems.

The Navy would like to add five F-35s to its aircraft buy, but its bigger desire is more attack submarines and warships, given its target of building up to a fleet of 355 ships. The Navy termed a second Virginia-class attack submarine its top unfunded priority in fiscal year 2021.It has set a requirement for 66 attack submarines and currently has about 50.However, as older Los Angeles-class submarines retire, that number could fall to 42. Forgoing construction of a Virginia-class submarine does not help to close that gap.

Moreover, the total number of Navy ships, now 293, will decline in the near term, widening the gap to get to 355.The Navys five-year shipbuilding program cut five of twelve planned Arleigh Burke-class destroyers, and cost considerations have led the Navy to decide to retire ten older Burke-class destroyers rather than extend their service life for an additional ten years.This comes when China is rapidly expanding its navy, and Russian attack submarines are returning on a more regular cycle to the Atlantic Ocean.

The Navy has said that funding the first Columbia-class ballistic missile submarine forced a cut-back in the number of other ships in its fiscal 2021 shipbuilding request.The decision not to fund a second Virginia-class attack submarine appears to stem directly from the unexpected $3 billion plus-up in funding for the National Nuclear Security Administrations fiscal year 2021 programs.

These are the opportunity costs of more nuclear weapons:fewer dollars for aircraft, ships, attack submarines and ground combat equipment for conventional deterrence and defense.

The principal driving factor behind the size of U.S. nuclear forces comes from Russian nuclear forces and doctrine.Diverse and effective U.S. nuclear forces that can deter a Russian nuclear attack should suffice to deter a nuclear attack by any third country.In contrast to the Cold War, the U.S. military no longer seems to worry much about a bolt from the bluea sudden Soviet or Russian first strike involving a massive number of nuclear weapons designed to destroy the bulk of U.S. strategic forces before they could launch.That is because, under any conceivable scenario, sufficient U.S. strategic forcesprincipally on ballistic missile submarines at seawould survive to inflict a devastating retaliatory response.

The most likely scenario for nuclear use between the United States and Russia is a regional conflict fought at the conventional level in which one side begins to lose and decides to escalate by employing a small number of low-yield nuclear weapons, seeking to reverse battlefield losses and signal the strength of its resolve.Questions thus have arisen about whether Russia has an escalate-to-deescalate doctrine and whether the 2018 U.S. nuclear posture review lowers the threshold for use of nuclear weapons.

If the United States and its allies have sufficiently robust conventional forces, they can prevail in a regional conflict at the conventional level and push any decision about first use of nuclear weapons onto the other side (Russia, or perhaps China or North Korea depending on the scenario).The other side would have to weigh carefully the likelihood that its first use of nuclear weapons would trigger a nuclear response, opening the decidedly grim prospect of further nuclear escalation and of things spinning out of control.The other sides leader might calculate that he/she could control the escalation, but that gamble would come with no guarantee. It would appear a poor bet given the enormous consequences if things go wrong.Happily, the test has never been run.

This is why the opportunity costs of nuclear weapons programs matter. If those programs strip too much funding from conventional forces, they weaken the ability of the United States and its allies to prevail in a conventional conflictor to deter that conflict in the first placeand increase the possibility that the United States might have to employ nuclear weapons to avert defeat.

For the United States and NATO members, that could mean reemphasis on an aspect of NATOs Cold War defense policy. In the 1960s, 1970s and early 1980s, NATO allies faced Soviet and Warsaw Pact conventional forces that had large numerical advantages, and NATO leaders had doubts about their ability to defeat a Soviet/Warsaw Pact attack at the conventional level.NATO policy thus explicitly envisaged that, if direct defense with conventional means failed, the Alliance could deliberately escalate to nuclear weapons.That left many senior NATO political and military officials uneasy.Among other things, it raised uncomfortable questions about the willingness of an American president to risk Chicago for Bonn.

Russia found itself in a similar situation at the end of the 1990s.With a collapsing economy following the break-up of the Soviet Union, the Russian government had to cut defense spending dramatically.As its conventional capabilities atrophied, Moscow adopted a doctrine envisaging first use of nuclear weapons to compensate.(In the past fifteen years, as Russias defense spending has increased, a significant amount has gone to modernizing conventional forces.)

The United States and NATO still retain the option of first use of nuclear weapons.If the U.S. president and NATO leaders were to consider resorting to that option, they then would be the ones to have to consider the dicey bet that the other side would not respond with nuclear arms or that, if it did, nuclear escalation somehow could be controlled.

Assuring NATO allies that the United States was prepared to risk Chicago for Bonn consumed a huge amount of time and fair amount of resources during the Cold War.At one point, the U.S. military deployed more than 7000 nuclear weapons in Europe to back up that assurance.Had NATO had sufficiently strong conventional forces, the Alliance would have been able to push that risky decision regarding nuclear first use onto Moscowor even have been able to take comfort that the allies conventional power would suffice to deter a Soviet/Warsaw Pact attack.

In modernizing, maintaining and operating a safe, secure and effective nuclear deterrent, the United States should avoid underfunding conventional forces in ways that increase the prospect of conventional defeat and/or that might tempt an adversary to launch a conventional attack.If Washington gets the balance wildly out of sync, it increases the possibility that the president might face the decision of whether to use nuclear weapons firstknowing that first use would open a Pandoras box of incalculable and potentially catastrophic consequences.

This means that the Department of Defense and Congress should take a hard look at the balance.The Pentagon presumably has weighed the trade-offs, though it is not a unitary actor. Nuclear weapons are our top priority has been the view of the leadership.The trade-offs have been easier to manage in the past several years, when nuclear programs were in the research and development phase, and defense budgets in the first three years of the Trump administration grew.As nuclear programs move into the more expensive procurement phase and the fiscal year 2021 budget shows little increase, the challenge of getting the balance right between nuclear and conventional spending has become more acute.It is not apparent that the Pentagon has weighed the opportunity costs over the next ten-fifteen years under less optimistic budget scenarios.

As for Congress, which ultimately sets and approves the budget, no evidence suggests that the legislative branch has closely considered the nuclear vs. conventional trade-offs.

All that was before COVID19.The response to the virus and dealing with the economic disruption it has caused have generated a multi-trillion-dollar budget deficit in 2020 and likely will push up deficits in at least 2021.It would be wise now to consider the impact of COVID19.

Having added trillions of dollars to the federal deficit, and facing an array of pressing health and social needs, will Congress be prepared to continue to devote some 50 percent of discretionary funding to the Department of Defenses requirements?Quite possibly not.If defense budgets get cut, the Pentagon will face a choice: shift funds from nuclear to conventional force programs, or accept shrinkage of U.S. conventional force capabilities andas the United States did in the 1950s and early 1960srely on nuclear deterrence to address a broader range of contingencies. In the latter case, that would mean accepting, at least implicitly, a greater prospect that the president would have to face the question of first use of nuclear weapons, i.e., a conventional conflict in which the United States was losing.

This is not to suggest that the U.S. military should forgo the strategic triad.Trident II SLBMs onboard ballistic missile submarines at sea remain the most survivable leg of the strategic deterrent.The bomber/air-breathing leg offers flexibility and can carry out conventional missions.The ICBM leg provides a hedge against a breakthrough in anti-submarine warfare.Moreover, if in a crisis or a conventional conflict, the Russian military were to develop the capability to attack U.S. ballistic missile submarines at sea, the Kremlin leadership might well calculate that it could do so without risking a nuclear response.Attacking U.S. ICBMs, on the other hand, would necessitate pouring hundreds of nuclear warheads into the center of America.A Russian leader presumably would not be so foolish as to think there would be no nuclear retaliation.

While sustaining the ICBM leg, one can question whether maintaining 400 deployed ICBMs, as the current plan envisages, is necessary.Reducing that number for the Ground-Based Strategic Deterrent (GBSD) would achieve budget savings, albeit later in the production run. Another question is whether some way might be found to extend the service life of some portion of the current Minuteman III force that would allow delaying the GBSD program, which is projected to cost $100 billion, by ten-fifteen years and postponing those costsfreeing up funds in the near term for conventional force requirements.

Another issue concerns the Long-Range Standoff Missile (LRSO) and its cost, estimated at some $20 billion when including the nuclear warheads.The B-21 bomber will incorporate stealth and advanced electronic warfare capabilities allowing it to operate against and penetrate sophisticated air defenses.The LRSO, to be deployed beginning in 2030, is intended to replace older air-launched cruise missiles carried by the B-52 bomber and could later equip the B-21 if it loses its ability to penetrate.

An alternative plan would convert B-52s in 2030 to conventional-only missions and delay the LRSO to a future point if/when it appeared that the B-21s ability to penetrate could come into question.By 2030, the Air Force should have a significant number of B-21s (the B-21 is scheduled to make its first flight in 2021 and enter service in 2025).With at least 100 planned, the Air Force should have a sufficient number of B-21s for the 300 nuclear weapons it appears to maintain at airfields where nuclear-capable bombers are currently based.

These kinds of ideas would free up billions of dollars in the 2020s that could be reallocated to conventional weapons systems.Delaying the GBSD and LRSO and their associated warhead programs by just one year (fiscal year 2021) would make available some $3 billionenough money for a Virginia-class attack submarine. Delaying those programs for ten-fifteen years would make tens of billions of dollars available for the militarys conventional force needs.

All things being equal, it is smarter and more efficient to choose to make decisions to curtail or delay major programs rather than to continue them until the money runs out and forces program termination. As it examines the administrations proposed fiscal year 2021 defense budget, Congress should carefully consider the trade-offs and press the Pentagon to articulate how it weighed the trade-offs between nuclear and conventional forces. In the end, Congress should understand whether it is funding the force that is most likely to deter not just a nuclear attack, but to deter a conventional conflict that could entail the most likely path to nuclear war.

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How COVID-19 might affect US nuclear weapons and planning - Brookings Institution