Strategic Tradeoffs in U.S. Naval Force Structure — Rule the Waves or Wave the Flag?
Editors note: This essay is the fourth in a series of eight articles, “Maritime Strategy on the Rocks,” that examines different aspects and implications of the recently released tri-service maritime strategy, Advantage at Sea: Prevailing with Integrated All-Domain Naval Power. Be sure to read the first, second, third, fifth, sixth, and seventh articles. We thank Prof. Jon Caverley of the U.S. Naval War College for his assistance in coordinating this series.
What kind of navy should the United States build with its defense dollars? Does America want one that will win wars? Of course. How about one that deters other nations from starting a war in the first place? No doubt. Perhaps it is also useful to have a navy that can “show the flag” to generate diplomatic and economic influence, or to bolster the liberal international order? And wouldn’t it be nice if Americans could have more guns, and more butter, while also lowering their taxes?
The common refrain when critiquing U.S. naval affairs is too often “too much” or “too little” — think of John Paul Jones’ famous quip, “Without a respectable navy — alas America!” Here, we instead ask readers to consider the inherent tradeoffs between what America buys, not just how much it spends.
Each of the goals outlined above is desirable in its own right, but their attractiveness as objectives does not mean that they are all equally achievable, or even that they can all be achieved at the same time, with the same navy. Different naval force structures — the mix of maritime platforms and capabilities — have disparate effects on various national goals and patterns of conflict (where and whether America fights). Military specialization to achieve one goal can compromise the ability to achieve other goals. The kind of navy that the United States acquires determines the characteristics of the world in which Americans operate.
Too often, the assumption underlying U.S. naval strategy seems to be that the “right” mix of ships and sailors will somehow allow America to achieve multiple, often incompatible, national security objectives. Advantage at Sea, the recently released tri-service maritime strategy, emphasizes five different goals: “generate Integrated All-Domain Naval Power;” “strengthen alliances and partnerships;” “prevail in day-to-day competition as we uphold the rules-based order and deter our competitors;” “control the seas” when deterrence fails; and “boldly modernize the future naval force to maintain credible deterrence and preserve our advantage at sea.” The last of these goals may be the most portentous, since decisions about what kinds of forces to acquire can lock in the nation’s strategic options for decades to come.
Advantage at Sea elides classic tensions in naval strategy by aiming to improve deterrence, global presence, and combat effectiveness in equal measure. However, these worthy objectives cannot all be met to the same degree, and in the same way, by any future U.S Navy.
In a recent study published in Security Studies, we examine the historical relationship between naval force structure and international politics. We present a detailed argument, grounded in rationalist models of conflict and extensive empirical evidence, about the distinctive nature of seapower. The statistical analysis we provide demonstrates that nations with bigger navies have disproportionate political influence over other nations, as measured by diplomatic recognition. We also find that navies project power further from home, ensuring that conflicts occur closer to a rival’s borders and farther from friendly shores. Both findings produce systematic evidence supporting what navalists expect.
Yet we further find that naval nations are more likely to experience conflict. After controlling for other explanations like the size or overall spending of a nation and geographic distance, countries with big navies seem to be more prone to fight wars. We find similar differences across naval platforms as for navies generally — for instance, submarines tend to be more destabilizing than aircraft carriers. These counterintuitive findings fly in the face of the conventional wisdom that navies enhance deterrence. How can we explain this and what do these findings imply for U.S. maritime strategy?
Specialization at Sea
The inherent tradeoffs posed by naval architecture have long been understood at the level of individual platforms. Larger-hulled ships carry more ordnance, conduct more diverse operations, and stay at sea for longer periods. Nuclear propulsion is a big advantage, but it takes a relatively large displacement to carry the necessary power plant and shielding. Armor protects a ship but slows it down and affects factors like crew comfort and handling. A faster, more maneuverable vessel can choose the time and place of an engagement, but speed costs in firepower, sea handling, or endurance (witness recent littoral combat ship debates).
Specialized vessels — frigates, carriers, submarines, amphibious assault ships — optimize different tactical characteristics. Navies can combine different platforms into task forces that achieve synergies together. But this still begs the issue of emphasis. Are more “attack” submarines going to trail surface vessels, providing protection against attack, or be cut loose to act as aggressive, silent killers? Certainly, having more attack submarines would lessen this dilemma, but often only by reducing the availability of surface or air platforms that accomplish other missions and achieve different political goals.
Similar considerations apply to landpower. Specialized combat arms — armor, artillery, infantry, aviation — fight together as combined arms teams. Such combinations of specialties and specialized platforms have enabled the United States to play a savvy, winning game of “rock, paper, scissors” with most of its enemies. But they don’t satisfy every objective. Specialization is about doing some things well and others more poorly. Even combined arms teams face hurdles that they cannot surmount. They may not consist of the right mix of forces for the threat, or they may simply be unable to operate in different domains.
While this logic of specialization and offset is well understood at the tactical or operational level of war, it is less appreciated at the strategic or political level. Indeed, some analysts tend to treat military power as an undifferentiated good, assuming that it is the aggregate contribution to military capacity that really matters for coercion, war, or reassurance. Just as naval architects have to juggle tradeoffs in hull design, arms, and armament, so too do planners have to consider that making militaries more effective at one strategic goal dilutes the nation’s ability to pursue other goals. Size certainly matters, but content also has consequences — building a large, hard-striking navy does not make a nation a dominant land power.
Yet official U.S. Navy strategy documents consistently assume that the sea services can and will be able to achieve disparate objectives. The very characteristics of naval power privilege some goals over others, even as how a nation allocates naval resources shapes the likelihood, performance, and outcome of each phase of competition or warfare. Prior to 2020’s Advantage at Sea, the 2015 Cooperative Strategy for 21st Century Seapower stated, “Naval forces achieve all domain access as part of joint operations, improving relationships and deterrence in peacetime and enabling success against our enemies in wartime.” Its 2007 predecessor stated similarly, “Maritime forces must contribute to winning wars decisively while enhancing our ability to prevent war.” Neither document acknowledges the inherent tensions between deterrence and defense, or indeed the tradeoffs in doing either with naval power.
Advantage at Sea likewise assumes that naval forces can deter war while also maximizing the prospects for victory. The U.S. Navy naturally wants to have its “peace” of cake and “fight” it too. Yet deterrence and defense are distinct strategies. Sometimes they can reinforce each other, but at other times they cannot. The statistical evidence we supply in our Security Studies article suggests that this tension is more pronounced for seapower.
The Maritime Commitment Problem
Regrettably, the very characteristics that make navies so effective at international influence make them less than ideal for deterrence. Consider the 2007 strategy’s emphasis on the “expeditionary character of maritime forces — our lethality, global reach, speed, endurance, ability to overcome barriers to access, and operational agility.” These are traits that would clearly seem to enhance warfighting. Naval combat places a premium on speed and surprise to concentrate mass at a given location and disperse just as quickly.
The same passage goes on to assume, however, that these useful warfighting characteristics will “provide the joint commander with a range of deterrent options” that enable “an approach to deterrence that includes a credible and scalable ability to retaliate against aggressors conventionally, unconventionally, and with nuclear forces.” Yet deterrence relies on the ability to credibly commit to carrying out a threat. A target has to believe that the deterrer will act if a red line is crossed. Anything that gives a target reason to suspect that the deterrer will balk tends to undermine credibility. Nuclear threats are particularly hard to make, precisely because the costs of nuclear war are so horrendous for whoever makes the threat.
While commitment problems are most pronounced for nuclear threats, they complicate other situations too. Politics privileges the artful lie — leaders have incentives to exaggerate their intentions or abilities to get a better deal. For the same reasons, their rivals have incentives to suspect a bluff. Actors who rely on secrecy for military advantage cannot advertise their strength, except in rare situations, since the act of revelation enables the target to undermine the threat. Any source of uncertainty about relative power, interests, and the costs of war in turn tends to make crises and war — deterrence failure — more likely.
Fleets composed of deadly but vulnerable warships rely on surprise for tactical advantage. This sows uncertainty. Warships use speed and stealth to concentrate when least expected and disperse when most threatened. However, the ability to hide and move (stealth and maneuver) also produces strategic instability. If the local balance of power is unclear to belligerents, or is subject to sudden change, then the risk of miscalculation grows as well. Navy doctrine tends to assume that “the sea is a vast maneuver space, where the presence of maritime forces can be adjusted as conditions dictate” (quoting the 2007 Cooperative Strategy) and, therefore, naval forces will “enable flexible approaches to escalation, de-escalation and deterrence of conflicts.” Yet it is precisely the ability to maneuver quickly, stealthily, and arbitrarily that undermines the credibility of coercive signals.
Building mobility into a force increases its lethality and power projection at the expense of credibility. Credibility varies on other dimensions, of course, not least of which is the inherent plausibility of a leader’s claims and the value of the stakes, which may offset the marginal liability of mobility or stealth. Yet because this marginal effect is real, it is important to recognize that money spent on different types of force structure has different effects on whether others believe what a leader claims. The very advantages of naval power that make it dynamic and flexible also make it less effective at overcoming any nagging doubts that allies and adversaries may have. Elsewhere we make an analogous argument about the destabilizing consequences of offensive cyber operations targeting nuclear weapons: the secrecy of the military means undermines the political ends. All desirable political goals do not follow from the same capabilities.
Navies offer a wider range of options for global influence, options that can be scaled to provide escalatory (or de-escalatory) actions in the practice of deterrence. But this same discretion encourages competitors to wonder whether any particular option will be exercised. The art of deterrence, after all, involves limiting one’s options, not increasing them. Thomas Schelling makes this point memorably in his discussion of “throwing the steering wheel out the window” in a game of chicken. Blue water navies give national decision-makers more options (levers or wheels) for projecting power over large portions of the globe. Yet this important, and inherent, advantage also comes with a liability. Naval forces cannot be deployed everywhere. Since they are mobile, leaders cannot as credibly promise that they will appear at any particular place under all conditions. Concentration here implies dispersion elsewhere. Because navies move swiftly, they might sail away, or simply never show up. Indeed, the arbitrariness of naval power played an important role in the American Revolution. Lt. Gen. Charles Cornwallis at Yorktown assumed that having his back to the sea was an advantage, but this turned into a liability when the Royal Navy failed to show up.
The Stopping Power of Land
Different operational domains (and platforms) offer different political advantages, and liabilities. As Francis Bacon famously observed, “He that commands the sea is at great liberty, and may take as much and as little of the war as he will. Whereas those that be strongest by land are many times nevertheless in great straits.” The same tradeoff exists for U.S. foreign policymakers. A capable navy can support more allies and cover more contingencies, even if it cannot be in two places at once. This mobility advantage expands options. Its disadvantage, however, is in credibility.
The cavalry in old Hollywood westerns was famous for showing up in the nick of time to chase off the bad guys. But the fact that the cavalry rode over the hill late in the action reveals a core problem. The wagon train was not adequately protected — it was attacked (and deterrence failed) because the bad guys decided that the cavalry would not arrive in time. The bad guys may have judged the opportunity wrong this time, but their bet was not in general unreasonable. Imagine instead a well-defended band of settlers, with soldiers already accompanying the column. Attacking such a target is inherently more difficult, and so deterrence is more likely to succeed. The tradeoff posed by this example is that there may not be enough soldiers to go around. Putting them on horses and allowing them to roam means that they can cover more territory and more wagon trains, if imperfectly.
Military history is replete with examples where hubris or simple miscalculation led to disaster and where soldiers and units that lacked the advantage of mobility became an impassible barrier to their enemy. Those who are most mobile turn and run, not because they are cowards, but because they can. The “bridge too far” of Operation Market Garden was not too far for the paratroopers who, once deployed, were largely committed in their positions (and fought with extraordinary valor). It was too far for the armored units that were slowly pounding their way to the rescue. During the battle for Guadalcanal, the U.S. Navy responded to a Japanese attack by retreating. The marines on Guadalcanal stayed, because they had no other option.
Especially on islands in the Pacific, land forces are inherently more likely to stay and fight, and thus are more effective at deterrence. Investment of specific assets in a given location might seem like a military disadvantage from the point of view of flexibility and survivability. Yet the reduced mobility and increased visibility of land forces provide key political virtues. Land-based forces demonstrate to allies and adversaries alike that a given location will be defended vigorously. Reduced mobility also means that land powers have to forego opportunities to rapidly redeploy to other locations, fostering assurance.
Deterrence works by creating an unacceptable (and credible) consequence for a given undesired action. There are several challenges in deterrence, most of which are well understood. One of the least studied is what might be called “aspiration creep.” Leaders often convert deterrence into compellence, using the power to discourage aggression against a given target to wrest greater influence elsewhere. A U.S. naval vessel in Yokohama, nominally protecting Japan, may find itself tasked to head to the Indian Ocean, say, because it is stationed relatively closer than other members of the Third or Seventh Fleets. Increasing naval power could discourage aggression, but it could also tend instead to lead to additional commitments.
Land-based forces (and to a lesser extent land-based maritime infrastructure) can be more useful than high seas forces for U.S. deterrence policy. Their usefulness increases where and when their inability to move about easily ensures that they commit the United States only where they are posted. Forward deploying troops, as opposed to sailing naval vessels, improves the credibility of U.S. extended deterrence by creating tripwires designed to mobilize a more robust U.S. response if attacked. Yet here too there are political tradeoffs. Maintaining troops abroad is expensive — indeed, this policy is a credible signal precisely because it is costly. It also exposes the United States to a heightened risk of under-provision and entrapment by easy-riding allies.
The United States can also help allies like Japan and quasi-allies like Taiwan to develop their own shore-based defenses. Strategies of “active denial” or “defensive defense” essentially turn China’s anti-access and area denial (A2/AD) techniques against it. Shore-based reconnaissance and strike forces would be less useful for attacking China directly. The same cannot be said of proactive offshore interventions by the U.S. Navy. Shore-based denial also reduces the risks of inadvertent escalation that are inherent in attacking command and control targets on mainland China, a likely feature of any U.S. campaign to roll back Chinese A2/AD. Of course, increasing the self-reliance of allies also reduces U.S. influence over them.
The Future Battle Force
Our perspective may be controversial, given prevalent assumptions about the strategic versatility of seapower in navalist thought. Yet it is also critical as the U.S. Navy, and the American people, debate significant changes in force structure. Advantage at Sea is short on details about future force structure beyond vague ambitions to “prioritize lethality, capacity, readiness, and expeditionary logistics over sustaining legacy capabilities.” Yet there are hints elsewhere of how the Navy might operationalize such sentiments.
Shortly before his sudden departure in early November 2020, Secretary of Defense Mark Esper unveiled “Battle Force 2045,” an ambitious plan for “500 manned and unmanned ships by 2045, and a fleet of 355 traditional battle force ships by 2035.” While Esper is gone, discussion among naval strategists suggests that his plan, or something like it, could survive. The plan represents a significant increase from today’s fleet of about three hundred (manned) vessels, as well as significant changes to naval force structure adding new light aircraft carriers, reducing large carriers, and nearly doubling the inventory of attack submarines, amphibious carriers, small surface combatants, and logistics ships, with unprecedented automation.
In our Security Studies article, we find differences across naval platforms regarding power projection and instability that parallel those for national naval power in general. Though always an issue in analyzing policy, we take a number of steps in the article to address the “chicken and egg” problem where effects can trigger putative causes. In an analysis using data covering the whole of the 20th century, we find that large surface combatants like battleships are associated with increased political instability relative to naval power in general, yet are less associated with power projection successes. Aircraft carriers are associated with slightly less instability, supporting the idea that carriers have a comparative advantage for deterrence, relative to other ship classes (but not land forces). Attack submarines, emblematic of stealth and firepower, are predictably associated with an increased risk of conflict. Different platforms operate in different ways, supporting different political objectives.
Our findings have three implications for future force structure planning. First, the addition of new light carriers and more amphibious carriers could marginally improve the U.S. Navy’s ability to “show the flag” and enhance political influence in more places. While frigates can be and often are used for naval presence, our analysis suggests that carriers are marginally more effective for this mission. Conversely, a reduction in large carriers could have a negative effect. We should qualify this claim by emphasizing that our data reflect national naval force structures not geographical employment patterns. Shallow draft frigates can go to many places that carriers cannot, which means that they can show the flag in places where carriers cannot.
Second, however, the addition of light carriers and amphibious assault ships is more than offset by a major investment, of nearly two hundred vessels, in attack submarines and surface combatants. These ship classes can be expected to complicate deterrence and increase instability. We find that diesel attack submarines are most destabilizing. While the United States has no plans to procure diesel boats, its future submarines are likely to exemplify the relevant strategic characteristics of speed and stealth. While modern missile-carrying destroyers and cruisers are hardly comparable to the battleships in our dataset, their effect on stability may still be negative as well.
Third, heavy reliance on unmanned vessels will tend to exacerbate the naval commitment problem. An adversary faced with unmanned systems, which reduce the cost of war for their user, will have trouble determining the combatant’s true resolve, precisely because they reduce the cost of war. How does the target of deterrence figure out whether robot ships are being used because they are more effective in combat or because an adversary is reticent to risk human casualties? Unmanned systems acquired in the hopes of reducing the costs of war could thus end up increasing the risk, and possibly duration, of conflict by reducing its informativeness.
Which Navy for the 21st Century?
Strategy is the art of setting priorities with finite resources. The nominal purposes of America’s historic investment in naval power has been to deter and stabilize relationships, signal U.S. resolve, and increase U.S. combat effectiveness. Our research substantiates a basic and intuitive point: Achieving all of these objectives simultaneously is untenable for any navy and is, in effect, an abandonment of strategy.
It is tempting to use more capable navies to cover more political bets. Naval nations end up intervening in more places, but often with less commitment or clarity of purpose. Global reactions to the so-called pivot to Asia are a case in point. Mobile strike forces with an expeditionary punch enable U.S. leadership to respond to unexpected crises in faraway places. Yet the exercise of military power in places other than planned attenuates force commitments in the Pacific, precisely where the pivot said that military power is needed most.
A heavy investment in highly mobile military capabilities will tend to weaken the goal of deterrence. As it implements Advantage at Sea, the United States may well have the might with something like “Battle Force 2045” to better defend Asian allies. But it will tend more often to use that power in other places, far from the Pacific, thus distorting U.S. posture over time in response to new hotspots and outpourings of tensions elsewhere. As America again thins its lines in the effort to extend itself further, it will experience additional rounds of instability in Asia that it is unlikely to be able to address efficiently.
A simpler, though perhaps non-intuitive, solution is to put ground-based forces in places that are America’s highest priorities. Security in the Pacific, for example, seems obviously to be a naval domain. But one of the best ways to prove U.S. priorities is with shore-based land and air forces that signal, and indeed provide, a clear commitment to a particular security partner. The Navy clearly will still prove pivotal in any contest in the Pacific. But a fight is paradoxically much less likely the more the United States invests in forces that signal defense and deterrence, rather than maximizing U.S. offensive options and influence. This is the tradeoff that America faces.
Erik Gartzke is professor of political science and director of the Center for Peace and Security Studies at the University of California, San Diego. He is the co-editor, with Jon Lindsay, of Cross-Domain Deterrence: Strategy in an Era of Complexity (Oxford, 2019).
Jon Lindsay is assistant professor of digital media and global affairs at the Munk School of Global Affairs & Public Policy and Department of Political Science at the University of Toronto. He is the author of Information Technology and Military Power (Cornell, 2020).