In contrast, it is far less appreciated that defenses can be structured such that an adversary concludes he would not be able to achieve his objectives quickly and cheaply, with a desirable degree of certainty, and at a tolerable level of risk. This is known as deterrence by denial, and it is how conventional forces contribute most as a deterrent. As I've observed previously:
Dating back to the late Cold War, there has been a
general consensus among deterrence theorists that conventional deterrence does
not necessarily require convincing a potential adversary that any military
aggression it might embark upon would be handily repulsed. Though such
defensive capacity represents an ideal, defenders can obtain conventional
deterrence by denial if an opportunistic antagonist is convinced that the
defender possesses conventional forces of sufficient capability, quantity,
readiness, and proximity to the contested area to ensure any conceivable
conventional offensive by the antagonist stands an unacceptable chance of
degenerating into a costly, risky, protracted, and indecisive conflict. (Pg.
118)
Whereas punishment can be delivered credibly and efficiently from a distance, conventional deterrent forces can only effectively impose denial—and thereby achieve credibility—when they are positioned forward. This does not mean the bulk of the defender’s forces must be positioned at the border with the opponent, let alone within a probable contested zone. Granted, the political objective of not ceding highly valued territories or waters to the opponent by default will generally require that some forces be positioned in these places. It is also worth noting there can be some advantages to selective ‘frontline’ positioning of defensive forces. Strategic advantages might include compelling an aggressor to incur the costs and risks of dislodging those forces; one particularly noteworthy example of this is Thomas Schelling's threat that leaves something (in this case, an ill-controllable escalation process) to chance. Operational-tactical advantages might include the likelihood that an aggressor’s own forces would become exposed to interdiction or counterattack once they clashed with the frontline defense.
By no means, however, does an entire defense have to be positioned that 'far' forward. Rather, a credible forward defense is one in which the bulk of the conventional deterrent force is positioned close enough to a potential contested zone such that they can arrest an aggressor’s operational tempo and progress in time to prevent a fait accompli, if not parry the aggressor’s offensive moves altogether.
It follows that deterrence credibility weakens if the bulk of a conventional deterrent is positioned beyond a range from which it can fill the above role. As I noted in my SSQ article:
The defender’s posture is predicated on permanently deploying adequate forces within the contested theater, as the prospective aggressor’s calculus takes into account the likelihood that reinforcements from outside the theater, not to mention the defender’s overall national military-economic potential, cannot be sufficiently mobilized in mass and time—even if it recognized and rapidly acted upon strategic warning of war (a historical rarity)—to prevent the aggressor’s first moves from securing either a formidable operational advantage or a fait accompli decision.
This does not mean transoceanic airlift and strike assets cannot play important roles in buttressing the defender’s in-theater deterrent, but the tyrannies of distance, fuel, payload volume, and time grant in-theater forces far greater credibility for denying desired spoils. Relatedly, movements of token forces toward the crisis zone to signal resolve, or the use of token “tripwire” forces in the crisis zone for the same purpose, are unlikely to do much to enhance credibility if the potential aggressor perceives at least one conventional option exists that the defender’s overall in-theater forces do not appear capable of foreclosing. (Pg. 119)
The seminal theoretical work on the question of how a conventional force’s position affects deterrence outcomes is in Paul Huth’s 1988 book Extended Deterrence and the Prevention of War. Huth hypothesized multiple factors that might affect the probability of extended deterrence success. Each of these factors contained variables that could be tested against the 58 major crisis cases between 1885-1983 that involved a great or regional power’s extended deterrence of direct aggression against an ally by another great or regional power. (Pg. 24-25) Huth decomposed the military balance between the defender and its ally on one side and prospective attacker on the other into three separate variables: the immediate, short-term, and long-term balances. He defined the immediate balance as “those land forces of the potential attacker in a position to initiate an attack and those land forces of the defender and protégé in a position to repulse such an attack.” (Pg. 58) He then defined the short-term balance as “the capacity of the attacker and the defender and protégé to augment the immediate balance of forces by mobilizing ground and airforce manpower as well as the first class of trained reserves.” He lastly defined the long-term balance as “the capacity of the defender and protégé and the potential attacker to build up their existing armed forces (army, air, and naval manpower) and to maintain an increased level of fighting strength by mobilizing the economy and civilian population for war.” (Pg. 60-61)
It is noteworthy that Huth excluded air and naval forces from the immediate balance, and naval forces from the short-term balance. It does not appear, though, that he did so because he dismissed those forces as being irrelevant to his crisis cases. Nowhere in his discussion of the theoretical relationships between military balances and deterrence does he devalue air and naval forces. In fact, throughout that discussion he refers to each side’s military forces or armed forces writ large. (Pg. 35-41) As his crisis cases all involve threatened attacks against physical territories, I believe that he focused his analysis on ground forces because he viewed them as being the combat arms most directly engaged in the confrontations. Nevertheless, in many of his cases it is historically recognized that the ground forces he counted in the immediate balances relied heavily upon air and naval forces for support. Few military tasks in these crises were more important than the establishment and protection of sea and air lines of communication needed to deploy and sustain ground forces while simultaneously pressuring the opponent’s lines of communication. The same is certainly true with respect to the naval support that would be necessary for the employment of the ground and air forces counted in the short-term balances. An interesting task for future research would therefore be to evaluate whether the air and naval balances—individually as well as when combined with each other and ground forces—affected the probability of successful deterrence across Huth’s cases.
In order to calculate the immediate balances across the cases, Huth researched the sides’ ground force locations and sizes. Short-term balances were calculated by tallying the opposing standing peacetime land and air forces that could be mobilized during a conflict’s first few months, then adjusting the ratios to account for the relative difference in distances the attacker’s and defender’s forces had to travel in order to be deployed on the defender’s ally’s territory. Long-term balances were established by coding the sides’ total armed strengths, industrial strengths, and population sizes using sources such as the Correlates of War project, with similar adjustments being made to account for distance as was done with the short-term balances. (Pg. 59-61) Deterrence success was defined as the potential attacker refraining from attack. (Pg. 69)
Huth then used a form of regression analysis to test each of his hypotheses and identify which variables provided the most explanatory power regarding extended deterrence success. He found that his model predicted the deterrence outcome in 84% of the cases, making his findings statistically significant. With respect to military balances, he found that the immediate and short-term balances correlated with the historical deterrence outcomes in almost all cases (95% and 97.5% respectively) while the long-term balances figured minimally. Deterrence failure was the overwhelming result when either defending forces “were not in a position to repulse the initial attack, giving the attacker a decisive advantage in the immediate balance of forces” or “the defender’s capacity to mobilize and reinforce local forces did not decisively alter the short-term balance of forces in its favor.” He found that deterrence failed “in only 1 of 24 (4%) cases in which the defender possessed a clear advantage in both the immediate and short-term balance of forces,” and that “in 88% (30/34) of deterrence successes the defender and protégé possessed comparable or superior military capabilities in either the immediate or short-term balance of forces.” He concluded that the most effective conventional deterrent is “the capacity of the defender to repulse an attack and deny the adversary its military objectives at the outset and early stages of an armed confrontation.” A defender’s ability to eventually defeat an adversary in a prolonged contest matters little to deterrence, he found, as “the potential attacker does not initiate the use of force with the intention to engage in a war of attrition.” Therefore, “deterrence based on the threat of denial is much more effective than the threat of punishment in a protracted war.” (Pg. 71-76)
Still, Huth admitted that his data collection could not account for what the potential attacker’s leaders’ actually perceived about the military balances and their prospects for success in each crisis case. He suggested that the size of his sample set made it improbable that those perceptions differed greatly from reality in the aggregate, but accepted that the possibility of such a divergence as a major error source. (Pg. 71-72) Nevertheless, as favorable immediate and short-term balances correlated so closely with historical deterrence successes, it seems quite likely that these balances factored significantly into the majority of the potential attackers’ leaders’ decision-making. Even if one were to give more credit to defenders’ uses of crafty bargaining strategies and resolute escalation strategies in the deterrence success cases, it should be obvious that the defenders would have been hard-pressed to establish credible ‘facts on the ground’ supporting diplomatic maneuvers if the potential attackers possessed dramatic advantages in the immediate and short-term balances. In this light, we see that the immediate and short-term balances may not be decisive on their own, but that they are an irreplaceable grand strategic ingredient in achieving deterrence success.
One could nonetheless interpret Huth’s findings to mean that conventional forces mobilized and then deployed over the span of a few months are as effective a deterrent as forward forces, and that therefore the former can be substituted in a large part for the latter. Remember, though, that one of the central objectives of conventional deterrence is to convince an opponent that his prospects for achieving his desired political objectives quickly and cheaply through forcible aggression are low. The specifics of what is to be deterred thereby define the necessary qualities for the deterrent. If the opponent is to be deterred from invading a very large swath of territory, and under the most favorable conditions for the opponent it would still take him weeks to neutralize the defender’s forward forces and then solidify his gains, then the defender’s standing peacetime forces in the rear that can be brought to bear during that period can matter as a deterrent. This was the logic behind the U.S. Return of Forces to Germany (REFORGER) concept during the mid-to-late Cold War. However, if the defender’s forward forces are perceived by the potential attacker as being incapable of bogging down the latter’s offensive momentum enough to prevent the seizure of major spoils or the achievement of a fait accompli, then the defender’s reinforcements from outside the combat theater possess no deterrence value. Forward defense is therefore the lynchpin of a conventional deterrent.
This becomes even clearer when we examine the specifics of several contemporary extended conventional deterrence situations facing the U.S. A limited-aims Russian invasion of Latvia, Lithuania, or Estonia similar to what occurred in the 2008 Russo-Georgian War or the ongoing Russo-Ukrainian War could be completed to Moscow’s satisfaction faster than it would take for U.S. and other NATO allies’ forces to intervene decisively. Arresting a Chinese invasion of one or more of Japan’s Southern Ryukyu islands, breaking up Chinese use of submarines and theater-range aerospace power to coercively pressure the lines of communication to American allies along and inside the First Island Chain, or shielding East Asian allies from Chinese or North Korean coercive missile bombardment campaigns would all demand the immediate involvement of forward deployed U.S. forces. The same would be true regarding the requirements for breaking up an Iranian missile bombardment campaign against one or more U.S. allies in the Mideast, or for thwarting an Iranian anti-shipping campaign in the Arabian and Omani Gulfs.
Arguments that Russia has no need to conventionally invade an adjacent NATO ally because it can use plausibly-deniable ‘indigenous’ proxies and “little green men” special forces to achieve its objectives, or that China can employ its coast guard and ‘civilian’ fishing fleet to incrementally capture gains in contested waters without resorting to conventional warfare, or that Iran can avoid direct military hostilities by using its terrorist proxies to unleash coercive mayhem fall flat because in each case it is the credibility of the U.S. and allied forward-deployed conventional deterrent that renders traditional offensive military options by these three countries fraught with risks and uncertainties for their respective leaders. What such ‘end-run’ strategies do highlight, though, is the need for a wider conception of conventional deterrence that includes the defender’s use of forward-deployed constabulary forces such as coast guards, national law enforcement agencies with paramilitary capabilities, and even state-controlled civilian militias (whether on land defending their local areas or at sea in fishing fleets) to exacerbate the aggressor’s costs, risks, and uncertainties. These expanded deterrent forces could also extend greater defensive presence—and deterrence coverage—over more areas at once. Forward military forces would thereby assume the critical role of latently supporting these lighter entities by loitering ‘just over the horizon,’ or perhaps closer if a situation dictates, to highlight the escalatory danger.
Where does all this leave the U.S. Navy-Marine Corps team? For one thing, it must double-down on making clear to policymakers and the general public the importance of forward defense to deterrence as made possible via routine peacetime forward deployments. If political leaders do not want to ‘name names’ of potential adversaries, then so be it, but that does not prevent naval leaders and advocates from speaking early and often to as many audiences as possible about how combinations of geography and contemporary ‘generic’ military threat capabilities interact under deterrence theory to carve out pivotal roles for U.S. naval forces. Similar arguments can also be levied to great effect against advocates of naval retrenchment at home (and force downsizing accordingly), ‘offshore balancing’ strategies, or the substitution of conventional (or economic) deterrence by punishment policies for conventional deterrence by denial policies.
We should reflect on how adept the U.S. Navy and Marine Corps were at articulating such talking points in the recent past. Consider the following U.S. Navy video produced in the mid-1980s to describe the then-extant Maritime Strategy: https://www.youtube.com/watch?v=xQTFtveAZQQ&feature=youtu.be. At roughly the 18:15 mark, the narrator—backed by a message-clarifying map—states that “conventional forces, properly positioned early on, can limit Soviet options for escalating to war.” Change the word “Soviet” to “potential aggressor” and you have a timeless talking point fully supported by conventional deterrence theory. Later, at roughly the 19:45 mark, the narrator outlines that the Maritime Strategy is structured to expect a Soviet first salvo against forward deployed U.S. Navy forces to open a war, and then implies that viable measures exist to absorb that attack and then move to seize the initiative. I’ll be discussing some of those measures later this week (and I’ve touched on several already in a previous article), but it should be recognized that the 1980s U.S. Navy saw fit to include talking points that emphasized the viability of a forward defense.
The evidence that conventional deterrence depends upon forward defensive positions is overwhelming. For a distant maritime power such as the U.S., this has major implications in terms of the overall force size necessary to permanently position some assets forward as possible, rotationally forward deploy other assets as necessary to round out the in-theater deterrent, and maintain rapid surge-ready assets at home and in adjacent theaters to buttress the forward defense in a crisis. None of this should be interpreted to downplay force capabilities and posture as core qualities of a conventional deterrent; those topics will be explored in subsequent posts.
We can therefore derive four tests related to force position that should be applied against any proposed conventional deterrence policy:
- Given a defending force’s capabilities, posture, and operational concept(s), are its assets positioned such that a potential adversary can be led to believe any conceivable conventional aggression will be quickly arrested if not repulsed?
- Are high campaign-value assets positioned in ways that lead a potential adversary to conclude that enough will survive a first strike/salvo to make follow-on operations by the defender viable?
- Are the concepts for rapidly reinforcing as well as logistically sustaining the defending force in wartime credible to the potential adversary?
- As far as the potential adversary can tell, is the defender’s force positioning politically sustainable in peacetime (with implications for its funding sustainability)?
Deterrence
policy concepts that fail any one of the first three tests are inconsistent
with the widely-accepted body of conventional deterrence theory, and therefore
are unlikely to be effective. Concepts that fail the fourth test raise the
question of whether the defender has over-committed, which in turn should lead
the defender’s political leaders to reevaluate their national interest
definitions. If those interests continue to call for the commitment under
review, then to avoid the strategic disaster of a deterrence bluff being called
the requisite political capital must be applied and budgetary resources
allocated. Implementing and sustaining a credible conventional deterrent is not
inexpensive, and anyone who claims it represents ‘defense on the cheap’ doesn’t
know what they’re talking about. Effective deterrence is, however, much less
costly in blood, treasure, and prestige than war.
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