The war in Ukraine—now in its third year—has caused North Atlantic Treaty Organization (NATO) member states to reflect on their own security. This reflection takes many forms, including the relationship between the United States and the European NATO states, the appropriate levels of members’ defense spending, the Russian conventional threat to Europe, and, most concertedly, the Russian nuclear threat.

Given Russian actions in Ukraine and its conventional and nuclear threats to NATO, it is worth exploring how NATO members can best deter such threats. Such analysis should consider the nature of the existing Russian threat, NATO’s defensive capabilities, and how NATO has deterred aggression historically. By conducting such analysis, NATO members can identify both existing shortfalls in their current deterrence postures and identify how they can strengthen deterrence strategies that could stave off Russian aggression.

Given the prioritization of China within U.S. defense policy,REF coupled with the need to focus U.S. resources and power to deter Chinese aggression,REF it is particularly important that European NATO members assume the primary burden of the conventional deterrence and defense of Europe.REF

Deterrence: First Principles

For the purposes of this Backgrounder, deterrence refers to the ability of an actor to discourage another actor from taking a specific action by denying him the benefits of the action (also known as deterrence by denial) or by instilling in him the fear of the consequences of taking such an action (also known as deterrence by punishment).REF

Deterrence by denial often focuses on active defenses (such as missile defenses) or conventional forces that prevent an actor from achieving military objectives. Less often, deterrence by denial incorporates a degree of resilience or redundance in the capabilities being targeted. In this sense, if an adversary tried to destroy the U.S. spaced-based satellite constellations using a nuclear weapon, a deterrence-by-denial strategy would incorporate the ability to field inexpensive replacement satellites rapidly. In this way, an actor that saw no benefit to destroying the U.S. satellite constellation (because it could be easily, rapidly, and inexpensively replaced) might well be deterred from pursuing such a course of action in the first place. Alternatively, missile defenses that shoot down enemy missile salvos targeted at the American homeland could deter an adversary from launching a missile attack in the first place if that adversary believed that any missile attack was doomed to failure.

Deterrence by punishment focuses on the ability of an actor to impose costs on an aggressor and ideally convince an aggressor that the costs he will incur will outweigh the benefit of any such action and thus be deterred. In this sense, an actor that launched a nuclear strike on another actor might face an even larger nuclear retaliation that resulted in unacceptable losses for his own side. Deterrence by punishment, of course, is not limited to nuclear punishment. Sanctions or conventional military responses are all potential deterrence actions that rely on the deterrence-by-punishment approach.

For deterrence to be effective, it must be credible. To be credible, a deterrence strategy must have the means to back up said strategy with specific capabilities, the willingness to employ those capabilities, and an effective communications strategy that conveys (at varying degrees of certainty) said capability and willingness to all relevant parties. Failure to do all three of the above undermines an actors’ deterrence strategy. As an example, a deterrence-by-punishment strategy that relied on nuclear retaliation would not be credible if the actor that was trying to deter did not have his own nuclear weapons or an extended deterrent guarantee from a nuclear-armed ally.

Similarly, if a leader issued statements about retaliations that were not at all proportionate to the action being deterred, that, too, would not be credible. As an example, a leader saying that he would use nuclear weapons to destroy a neighboring state if the state did not agree to a proposed trade agreement would not be seen as credible because it is unclear if any leader would be willing to destroy an entire nation over a single trade agreement. Similarly, if a leader was known for making clear statements about what he or she would not allow and set numerous “red lines”—and then failed to enforce said red lines—actors around the world would question the will of that leader, thereby undercutting the efficacy of that state’s deterrence posture.

Finally, a state must convince the target of a deterrence message that its actions could result in a significant (very possibly nuclear) response. Such a deterrence message could be stated explicitly, either publicly or privately, or implied with varying degrees of ambiguity. (The threat that leaves something to chance.) Conversely, relying on missile defense as a deterrence-by-denial strategy—but not disclosing said missile defense before an adversary launches a strike—would not be an effective deterrence strategy, as it failed to convince the deterrence target not to attempt missile strikes in the first place.

To recap: For deterrence to be effective, it must deter a specific actor (say, China) from taking a specific action (say, invading Taiwan), and it must be credible by having the capability to back it up (sufficient military forces to deny the occupation of Taiwan), the will to do so (a President willing to employ those forces), and a communicated declaratory policy that conveys its intentions either explicitly (a senior official who says repeatedly that Taiwan has a “rock solid” security guarantee) or ambiguously (the threat that leaves something to chance through strategic ambiguity).

NATO’s Early Cold War Posture: Deterrence Through Conventional Forces and Nuclear Advantage, 1947–1961

In the early Cold War, the Western democracies worried about Soviet-backed communist expansion into Europe. After subverting coalition governments in Poland and Czechoslovakia, Soviet proxies attempted to subvert or overthrow governments across much of Europe, including France, Greece, and Italy. Soviet pressure manifested itself in multiple ways, including the Berlin airlift crisis and a civil war in Greece.

Once the immediate political crisis of the post-war governments was settled by the late 1940s, both the Western democracies and the Soviet-dominated East began to rearm following the post-war demobilization. The United States then decreased its military strength from 3.1 million people under arms to 391,000 by 1947, with similar relative drawdowns across Britain and France.

By the late 1940s, however, as relations with the Soviet Union deteriorated and the Cold War began to develop, the West began to reverse course.REF By 1949, NATO (then a new military alliance) decided to field large military forces to deter a Warsaw Pact invasion of Western Europe.

This situation was a combination of deterrence-by-denial and deterrence-by-punishment strategy. NATO believed that by fielding a robust conventional military force it could deny the Soviets and the Warsaw Pact a successful invasion of Western Europe by inflicting severe damage on the Soviets. At the same time, the very act of using military force to deny Soviet objectives—which may have included strategic and conventional bombings of targets inside the Soviet Union itself—would incorporate deterrence by punishment. The concept of massive buildups of NATO forces is made clear by the 1952 Lisbon Communique, in which the North Atlantic Council said that NATO states would begin with “the earliest building up of balanced collective forces to meet the requirements of external security within the capabilities of member countries.”REF

By the early 1950s, NATO began to field massive numbers of conventional forces in Europe to deter a Soviet-backed invasion of Western Europe. NATO’s fielding of large conventional numbers was meant to convince the Soviet leadership not to initiate war just as much as it was designed to win a war should the Soviets decide to invade. The goal was war avoidance through a combination of deterrence by denial and deterrence by punishment.

Today, it is easy to forget how many Allied forces were stationed at the front lines of the Cold War. The United Kingdom had four entire divisions in West Germany alone, with as many as 130,000 troops.REF By 1952, the United States had more than 250,000 military personnel across Europe, eventually reaching a high-water mark of 400,000 by the beginning of the 1960s.REF Meanwhile, West Germany itself fielded a military of half a million, with 12 heavy-tank divisions providing the backbone of NATO’s conventional force in Europe.REF By 1955, NATO fielded 25 active divisions and 25 reserve divisions in Europe.

As impressive as these numbers are, it became apparent to policymakers in Washington before the end of the first decade of the Cold War that NATO ground forces were facing a quantitative disadvantage that they would be hard pressed to overcome—particularly given that a significant number of those NATO forces were devoted to occupation—as opposed to combat—duty in West Germany.

Indeed, a potential Soviet invasion of Europe was an omnipresent threat—and given the estimated size of Soviet-backed Warsaw Pact forces, such an invasion may have been successful. As the 1950s wore on, NATO force planners watched an ever-growing threat manifest on the other side of the Iron Curtain. By the mid-1950s, NATO estimated that the Soviet Union had approximately 2.5 million to 2.8 million troops in its ground forces, with 26 divisions comprising half a million soldiers deployed across Eastern Europe—with 10 heavy armored divisions and 10 motorized divisions stationed in East Germany alone.REF The Soviet army stationed 6,000 tanks in East Germany. NATO estimated that the 26 divisions in Eastern Europe were backed up with 75 divisions in Russia east of the Ural Mountains which were equipped with 29,000 tanks. These forces were again backed up with another 40 to 125 reserve divisions that could be mobilized within 30 days. In addition, Western defense planners estimated that non–Soviet Union Warsaw Pact nations fielded an additional 800,000 men across 60 divisions.REF

At the same time during the early Cold War, the United States was assuming greater defense commitments, particularly in East Asia, as it was rebuilding Japan, defending South Korea from communist invasions from the north, and supporting Taiwan from invasion from mainland China.

Given the disparity in manpower and the need for significant military capabilities in both Europe and Asia, the United States came to a bipartisan consensus that matching the communists conventionally was a losing proposition, as it was unclear that the West could field the conventional forces necessary to deny the Soviets from invading Western Europe. Nor was it all clear that the punishment these conventional forces could impose on the Soviets was severe enough to deter an invasion to begin with. Then-Secretary of State Dean Acheson in his memoirs noted that the estimated annual costs to field a force comparable to that of the Warsaw Pact would be roughly $50 billion—this at a period when the Defense Department’s annual budget was $13 billion.REF

Some type of offset was needed to overcome the communists’ conventional advantage without bankrupting the United States or its allies—all of which were still rebuilding from the Second World War.

By 1957, the Eisenhower Administration adopted the “New Look” strategy to offset Soviet ground superiority by leaning into an American comparative advantage: nuclear weapons and airpower.REF By building a large bomber force capable of penetrating Soviet air defenses and dropping nuclear weapons on Warsaw Pact nations, the Eisenhower Administration sought to deter Soviet aggression by threatening “massive retaliation.” This clearly was nuclear deterrence by threat of punishment and helped to launch both Strategic Air Command and the ground-based intercontinental ballistic missile (ICBM) nuclear force. Nuclear weapons, under the Eisenhower Administration, became the cost-effective offset designed to counter Soviet conventional advantage and, ultimately, deter Soviet-sponsored attacks. It simply required the capability and willingness to use nuclear weapons to annihilate Soviet and Warsaw Pact forces—both of which the United States had under President Eisenhower.

NATO’s Mid–Cold War Posture: Deterrence Through Flexible Response, 1962–1981

In 1961, the Kennedy Administration came to power at a time of reassessment of the Soviet threat. The Sino–Soviet split demonstrated that communism was not a monolith. Khrushchev called for “peaceful coexistence” with the West—while still claiming that the Soviets would “bury” NATO.REF At the same time, Washington was promoting a series of interlocking regional alliances based on NATO, to include the Southeast Asia Treaty Organization (SEATO) and numerous bilateral security alliances with Japan, Korea, and Taiwan.

From its outset, the Kennedy Administration was dubious about the credibility of the Eisenhower Administration’s “New Look” with its emphasis on massive retaliation, particularly given the Soviet Union’s investment in long-range missiles that could carry nuclear payloads to almost any target on the planet. For the new Administration, “the threat of massive retaliation could remain credible only if U.S. nuclear forces enjoyed clear superiority”—which by the early 1960s was not evident.REF

Secretary of Defense Robert McNamara found “RAND’s analyses of controlled escalation especially appealing.”REF In addition, the development and fielding of hardened silos for land-based ICBMs and difficult-to-detect ballistic missile submarines created the possibility for an adversary to ride out a massive nuclear retaliation and then strike back using survivable nuclear forces.REF The Soviet development of such capabilities meant that Eisenhower’s New Look threat of massive retaliation to a conventional invasion of Europe by the Soviets would soon no longer be credible due to the Soviets’ growing ability to inflict massive punishment on the United States through their second-strike capabilities. Consequently, the Kennedy Administration developed “Flexible Response” as the overarching deterrence strategy for the 1960s.REF

Flexible Response emphasized the development and fielding of capabilities that could respond to a variety of threats, from special forces to support counterinsurgency operations across the developing world to eventually building and fielding multiple independent re-entry vehicles (MIRVs) for nuclear warheads that could be mated to submarine-launched ballistic missiles and ICBMs.

In addition, nuclear employment strategy changed. In 1962 at the University of Michigan, Secretary of Defense McNamara announced that the United States would not directly target cities (known as countervalue targeting), but instead use lower-yield nuclear weapons to destroy enemy conventional military targets (counterforce targeting).REF The Allies would still field huge numbers of conventional forces—but they would be augmented not just by America’s ability to respond massively to Soviet nuclear use but by new generations of more limited nuclear options.

By the mid- to late-1960s, NATO adopted a strategy and fielded the weapons systems necessary to give NATO the ability to respond to Soviet aggression with conventional or nuclear systems. Indeed, NATO’s strategy at this point centered on allowing “NATO a greater flexibility and to provide for the employment as appropriate of one or more of direct defence, deliberate escalation and general nuclear response, thus confronting the enemy with a credible threat of escalation in response to any aggression below the level of a major nuclear attack.”REF

Thus, the key feature of the new NATO strategy that was evolving by 1967 was not just flexibility, which had already been a feature of earlier NATO strategy documents, but the idea of managed as opposed to episodic or even spasmodic escalation.

Indeed, the Flexible Response strategy did not dictate or tie NATO to a specific course of action in the face of a Soviet invasion—instead it emphasized adaptability that included the potential for NATO to employ short-range and medium-range tactical nuclear weapons first in the face of a Warsaw Pact conventional invasion of Western Europe.

This proliferation of distinct types and ranges of nuclear weapons resulted in enormous nuclear weapons arsenals on both sides of the Iron Curtain. While the Soviet Union fielded more than 6,000 nuclear weapons by 1965, the United States had more than 30,000 weapons.REF

Meanwhile, both the Warsaw Pact and NATO fielded enormous conventional forces in the mid–Cold War period. By the 1970s, the Warsaw Pact had 19,000 tanks in Northern and Central Europe alone (as opposed to NATO’s 7,000 tanks in the same area), with close to 100 Soviet divisions in Europe backed up by roughly 60 non-Soviet Warsaw Pact divisions, with around 1.5 million men under arms in active duty—backed up by roughly two million men in the reserves.REF In comparison, NATO could expect to field a force of 1.8 million men in Europe several weeks after the onset of conflict by mobilizing its reserves.REF Coupled with fears of an eroding technological edge, NATO and U.S. officials increasingly began to question whether even Flexible Response was sufficient to deter Warsaw Pact aggression.

What is striking about the middle Cold War years is not just the size of the Soviet and American conventional forces and strategic arsenals, but the decisions made by national policymakers about how to posture relevant capabilities and distribute “use authorities” to make nuclear threats credible. Indeed, by 1967, the NATO concept for the defense of the Alliance noted that if a direct defense with conventional forces did not stop an invasion force immediately, the Alliance would escalate with nuclear weapons to make “the costs and risks disproportionate to the aggressors’ objectives.”REF Targets of such strikes would be confined to NATO states, non-Soviet Warsaw Pact states, or those at sea.REF If targeted nuclear escalatory strikes failed to stop the Warsaw Pact advance, then follow-on and general release authority would be granted.REF General release authority meant, in short, that NATO field commanders would be authorized down to the division level to employ short-range and medium-range tactical nuclear weapons in order to defeat a Warsaw Pact invasion of Western Europe.REF

This delegation of release authority to the division level—after the President gave approval for the employment of nuclear weapons and NATO’s North Atlantic Council agreed, along with the Supreme Allied Commander in Europe, and after a series of select, targeted escalatory strikes on non-Soviet Warsaw Pact targets—was a means to make nuclear threats credible in the face of a Soviet leadership that might reasonably doubt Washington’s resolve to unleash nuclear weapons in the defense of Europe.

Flexible Response, in short, was innovative in that it improved NATO’s deterrence posture to one that sustained emphasis on deterrence by denial (conventional forces supported by nuclear use for operational effect, with the threat of the latter made credible by operational necessity, broad declaration, and delegation of release authority) with a new emphasis on deterrence by punishment. This new emphasis on punishment was enabled by increasingly capable strategic forces with a credible threat to use as enabled by delegation of lower-use authorities, thereby setting in motion a “threat that leaves something to chance.” The threat of punishment highlighted the unignorable possibility in the Soviets’ view that a Soviet assault would result in NATO nuclear employment, which could precipitate escalation to ever higher levels of violence and intensity, regardless of any question of whether U.S. leaders would rationally seek to go to those levels a priori. In this way, Washington sought to strengthen its ability to deter the Soviets from invading Western Europe through a combination of deterrence by denial and by punishment.

NATO’s Late Cold War Posture: Deterrence Through Conventional and Nuclear Advantage, 1982–1991

By the early 1980s, the Cold War was reaching its climax. Ronald Reagan was elected on a “we win, they lose” national security platform.REF This required doubling defense procurement, with the U.S. military researching and programming to buy new tanks, stealth bombers, munitions, a 600-ship navy, and new types of nuclear weapons, to include MX and Peacekeeper nuclear missile systems.REF Ronald Reagan also pursued land-based and space-based missile defenses aimed at undermining what at that point was a significant Soviet nuclear advantage.

In this sense, Reagan pursued a strategy designed to force the Soviet Union to make a choice: match U.S. defense spending and run the risk of bankrupting itself or allow the economically stronger United States to achieve military advantage over the Soviet Union. Ultimately, the Soviet Union chose the former, which accelerated its economic collapse. Indeed, the Soviet leadership’s reaction to the Reagan build-up resulted in the Soviet Union “spending three times as much as the United States on defence with an economy that was one-third the size.”REF

The number of forces and associated platforms fielded by NATO and the Warsaw Pact by this point is staggering. By the mid-1980s, the Warsaw Pact fielded roughly 4.5 million men under arms in Europe alone, spread across 295 divisions, with almost 70,000 tanks and 14,000 combat aircraft.REF In comparison, NATO fielded slightly more than three million men under arms in Europe spread across 170 divisions, with roughly 28,000 tanks and 12,000 combat aircraft.REF

There was of course a deterrence component to the Reagan military build-up: By fielding a conventional force that the Soviets could not possibly defeat (deterrence by denial) and would in fact suffer significant costs if they tried to attack (deterrence by punishment), the Reagan military build-up followed a strategic logic that blended Eisenhower’s New Look (massive retaliation) with Kennedy’s Flexible Response (the ability to inflict varying levels of violence and pain upon one’s adversary).

NATO’s Deterrence Posture in the Post–Cold War Era, 1992 to Today

Almost immediately after the Cold War ended, the United States and Europe began to disarm. The de facto dissolution of the Warsaw Pact in 1989, followed by its de jure dissolution in 1991, and combined with the dissolution of the Soviet Union in late 1991 meant that the chances of an invasion of North America or Western Europe were minimal.

Indeed, the economic collapse of Russia itself in the early 1990s required a massive shedding of its military power. The comparison of NATO forces at the end of the Cold War with those of NATO 2014 is striking. By the end of the Cold War NATO had 13 million people in the active and reserve military, 32,000 tanks, 11,000 aircraft, and 24,000 nuclear weapons.REF By 2014, despite expanding into the former Warsaw Pact nations and enjoying a population 45 percent larger than in 1986, NATO had only six million people in the active and reserve military, 7,000 tanks, 6,000 aircraft, and roughly 5,000 nuclear weapons.REF

During this period, the Russians maintained a sizable non-strategic nuclear arsenal—and the United States downsized its own theater nuclear arsenal. The United States dismantled thousands of nuclear weapons deployed in Europe, retired the sea-launched nuclear Tomahawk missiles, leaving the United States with only a small number of Cold War–era gravity bombs in Europe which it could employ in times of conflict.REF

NATO, for all intents and purposes, lacked any cohesive deterrence strategy in the post–Cold War era and in many ways “coasted” on the investments and capabilities of the late Cold War. NATO’s 1999 “Strategic Concept” document, the first of the major post–Cold War NATO statements, noted that the “Alliance has an indispensable role to play in consolidating and preserving the positive changes of the recent past, and in meeting current and future security challenges…. It must safeguard common security interests in an environment of further, often unpredictable change.”REF One would be hard pressed to find a more nebulous agenda or strategy uttered by a military alliance.

At the same time, the United States engaged in several relatively minor operations, to include the Persian Gulf War, peacekeeping operations in the Balkans and the Horn of Africa, and the air campaign over Kosovo and Serbia. From 2001 to 2018, the United States prosecuted a Global War on Terror on four different continents and two nation-building exercises in Iraq and Afghanistan.

Over the same period, NATO in Europe largely had demilitarized—and Russia was slowly but surely rearming. Vladimir Putin’s 2007 speech at the Munich Security Conference was a broadside aimed at the European security order, in general, and the United States, in particular, accusing Washington of creating a unipolar world “in which there is one master, one sovereign.”REF This speech was a warning bell to many in Washington who recognized that while Russia did not have the strength to threaten American interests directly, it could threaten the territorial integrity of a largely disarmed Europe.

Given that America’s adventures in Iraq and Afghanistan were not going well, American policymakers—including Presidents George W. Bush and Barack Obama—began to privately and publicly urge their European counterparts to do more. The need for Europe to do more became even more evident following Putin’s decision to maintain the Russian non-strategic nuclear arsenal, which is 10 times the size of the American non-strategic arsenal.REF

By the mid-2000s NATO agreed—in principle—to spend more on defense. In 2006 and again in 2014, NATO states agreed to spend 2 percent of gross domestic product (GDP) on defense—a number that only a small fraction of European states met in the decade and a half after they committed to do so.REF

In 2014, Russia invaded Ukraine and annexed Crimea. For some—but not nearly enough in Europe—this was a wake-up call that Russia was once again a threat to European peace and security. Indeed, the demilitarization of Europe continued throughout this period. When the Berlin Wall fell in 1989, the German Army had more than half a million active-duty members. Five years after the invasion of Crimea (and 11 years after the Russian invasion of Georgia), the German army had dropped by almost two-thirds—despite having 20 million more citizens due to the absorption of the East Germany by West Germany.REF Many U.S. policymakers were frustrated with the failure of much of Europe to re-arm—but at the same time, they did little to incentivize European rearmament.

By 2018, President Donald Trump’s National Defense Strategy noted that the United States military would increasingly focus on threats from China and that European NATO allies would have to significantly increase their role in the conventional defense of Europe.REF The Russian invasion of Ukraine in 2022, of course, changed the discourse in Europe about the threat that Russia poses to NATO itself, with more—but far from all—European NATO members increasing their defense budgets to deter further Russian aggression.

The Current Russian Threat

The threat from Russia—both to the United States and to Europe—should be examined with a sober eye and not be underestimated nor overestimated.

Almost immediately after it became clear that the war in Ukraine would not be short or decisive, Moscow began to rattle its nuclear saber in an attempt to intimidate the West from providing military support to Kyiv.REF Indeed, by the fall of 2022, the United States’ intelligence community believed that the chances of Russia employing low-yield, non-strategic nuclear weapons (NSNWs) was 50 percent.REF The Russian threat of battlefield, theater-range nuclear employment continued through 2023 and into 2024, depending in part on the ebb and flow of the battlefield in Ukraine, various strikes on Russian critical infrastructure, and even terrorist attacks.REF

The Russian NSNW threat poses some unique problems for NATO, particularly its members in Europe. As noted, Russia’s NSNW arsenal size is 10 times the size that of the United States. Indeed, the Federation of American Scientists estimates that Russia has roughly 2,000 NSNWs in its arsenal.REF Such weapons can be deployed from a variety of delivery platforms, including aircraft, artillery, or fixed or mobile missile launchers.REF Most of these weapons are optimized to reach short-range to intermediate-range targets, meaning that given their storage locations in Russia’s Western Military District, they can reach most of Western Europe.REF In addition, these weapons range in yield from several hundred kilotons of explosive power to potentially the sub-kiloton level—far below the explosive power of what the United States dropped on Nagasaki.REF

The United States only has about 100 to 200 operationally deployed NSNWs, primarily based in Europe.REF This is a 10-to-1 advantage in Russia’s favor when it comes to numbers of NSNWs. Further, the vast majority of these non-strategic weapons are B-61 gravity bombs.REF These are effective weapons and very capable—but they are gravity bombs that must be dropped over a target by a tactical fighter-bomber or from a strategic bomber over an enemy’s integrated air defense system. They do not have the “stand-off” ability of a nuclear-armed cruise missile—fired from hundreds or even a few thousand miles from a target. This is in stark contrast to the variety of nuclear bombs, cruise missiles, or ground launchers fielded by the Russians. Finally, the maximum yield of the B-61 is only about 50 kilotons—far below that of the Russian nuclear yields, which can go up to a few hundred kilotons.REF

In short, Russia’s NSNW force is larger and far more diverse than that of the U.S. or the NATO NSNW force.

Why does this matter? The ability to launch low-yield weapons from a stand-off range—that is, beyond the bubble where air defenses can credibly intercept an aircraft—means that there is a greater likelihood of the weapon hitting its target. Further, the dual-capable nature of the launchers—whereby some missiles can deliver nuclear or conventional warheads—means that it is exceedingly difficult, if not impossible, to identify the warhead on certain missiles before impact.

In addition, the ultra-low sub-kiloton yields on some Russian NSNWs means that Russia can target and strike military targets across Europe with nuclear weapons that inflict virtually no collateral damage on civilian population centers. And given the small number of NATO NSNWs, NATO would be hard pressed to respond in kind in a proportionate fashion. Put another way, Russia has nuclear advantage over the West in numbers and diversity of nuclear weapons, meaning that it can attempt to leverage that advantage in operational and coercive perspectives (as it has tried to do with its various nuclear threats to the West over the past several years). With only a few exceptions, then, virtually any NATO nuclear response to a Russian nuclear strike likely would require NATO to employ larger-yield nuclear weapons, given the disparity in arsenal size. Such an escalation is of course possible, but it is at least plausible to think that Moscow may see a path by which it could strike purely military targets with low-yield nuclear weapons, cause virtually no civilian casualties or downwind range radiological hazard, and believe that NATO would not employ nuclear weapons in kind.

A significant challenge is the fait accompli, in which Russia uses localized military advantage to cross into a NATO member’s territory (such as Finland, one of the Baltic nations, or Poland), gain lodgment, and offer peace talks with NATO, either to propose new borders based on the Russian lodgment or offer to exchange conquered new territory for a “new security architecture” in Europe, in which certain Eastern European countries would accept neutrality (that is, leave NATO) in exchange for Russian forces leaving their territory. Such a fait accompli requires moving suddenly, rapidly, with little strategic warning, and achieving limited military objectives before the adversary has time to react, much less form and field a credible defense. At that point, Russia can offer NATO a fait accompli, by which NATO can accept some kind of amended security or border reality or choose to reinitiate a conflict against Russian forces in defensive positions.REF

Should NATO instead choose to try to expel Russian forces from the occupied NATO territory, it would do so knowing that Russia has the advantage in low-yield NSNWs and may employ them against NATO forces to ensure that Russian forces would not be ejected from their positions. While it is unknowable whether Russia would employ nuclear weapons in such a scenario, it is plausible that such a potentiality would give NATO’s North Atlantic Council pause before deciding on a unified course of action. In this sense, Russia’s nuclear advantage and unitary decision-making, compared to a NATO that suffers from theater nuclear disadvantage and a requirement to get to consensus among 30-plus allies, means that Russia may believe it has an opportunity to initiate conflict with a high probability of success.

Indeed, it is clear that Russian leaders believe that their nuclear arsenal is the reason why NATO has not entered the Ukraine war as a cobelligerent. Dmitry Medvedev, deputy chair of Russia’s Security Council and the former president of Russia, says this about Russia’s nuclear weapons: “[W]e would have been torn to pieces without them.”REF

In addition to Russia’s NSNW advantage, it is clear from multiple sources that Russia is putting its economy and its manufacturing base on a wartime footing.REF Russia will soon be able to build roughly two million artillery shells a year, 100 new tanks a month, and is expanding its capacity to build long-range cruise and ballistic missiles.REF Indeed, some analysts suggest that roughly a third of Russian government spending is focused on military efforts, and has more than doubled since before the war.REF Some analysts believe that in 2024 Russia will call up somewhere between 400,000 and 1.5 million additional men to continue the fight in Ukraine and increase its force presence along its borders with Finland, the Baltics, and NATO.REF If this all manifests, it will represent a massive expansion of Russian military capabilities that will make up for losses in the Ukraine war and present a credible, if still localized, military threat to NATO states bordering Russia.

In addition, there seems to be a type of bloodlust in Russian statements. In addition to Putin’s near constant threats to use nuclear weapons on the West, to include stating that Russia is “ready for nuclear war,” there are the statements that seem to indicate that the entire European order should be overturned and the Russian empire should be re-established.REF Medvedev refers to the Baltic states as “Russian provinces” and says that Poland is “temporarily occupied.”REF Indeed, Medvedev goes even further saying that the reason he is so “harsh” to the West is “I hate them. They are bastards and degenerates. They want us, Russia, to die. And while I’m still alive, I will do everything to make them disappear.”REF

Russian leaders regularly deride Western statements and openly fantasize about nuclear war to such an extent that it is difficult to shake the feeling that there is a strain of thought within the Kremlin that believes that some kind of bloodletting is necessary. The statements by Putin, Medvedev, and Dmitri Trenin (a Moscow strategist with close ties to the Kremlin) are reminiscent of the statements of Nazi party members in the run-up to World War II—and quite different from the statements of the Soviet leadership during the majority of the Cold War. Khrushchev, Brezhnev, and their successors who embraced competition and even proxy wars never gave the sense of welcoming a nuclear cataclysm with the West. This raises the obvious question—what is the West’s ability to deter conflict with a nuclear-armed adversary that is paranoid, angry, and may even welcome a nuclear exchange as a means to satiate some kind of irrational desire for a bloodletting? Such speculation is armchair psychology at best, but it is well worth considering whether the West has ever attempted to deter a nuclear-armed quasi-fascist state led by men who fantasize about nuclear annihilation.

The Current State of European Defense

If Russia is arming up, what then is the status of European defense today?

In short, it is not good.

European NATO states are struggling to get their defense budgets where they need to be. Nearly 20 years ago, the North Atlantic Council determined that all NATO member states should spend at least 2 percent of their GDP on defense. Today, less than two-thirds of all NATO members have reached that mark. The current Supreme Allied Commander in Europe, General Christopher Cavoli, said that “two percent is a floor, not a ceiling” in Senate testimony—intimating that spending should be significantly higher.REF

Moreover, many European militaries have shrunk as well. Today, the United Kingdom has fewer people in its military than the U.S. Marines Corps—and the Royal Navy only has a fleet of 16 surface combatants.REF The German army, once so formidable in the Cold War, is a shadow of its former self, with only 100 or so main battle tanks fit for service.REF Indeed, NATO’s military forces—particularly in Europe—are significantly smaller than they were in the Cold War despite NATO being significantly larger (having essentially added the former non-Soviet Warsaw Pact nations to the Alliance, along with Sweden, Finland, and the Baltic States) economically, technologically, and demographically than it was in the Cold War.REF Indeed, Europe’s economy in 2023 was seven times the size of that of Russia.REF

As Europe and the United States have given Ukraine significant military assistance over the past two years, to include munitions, air defenses, and platforms, thus lowering their own magazine depth, the question arises—is NATO, particularly European NATO, prepared to deter Russian aggression against NATO itself?

The answer to that question is maybe. And maybe not.

Europe is rearming and increasing its defense budgets—but its own defense industrial base is not tooled for a sustained wartime economy the way Russia’s is. New munitions plants are opening in Eastern Europe, but it will be years until those plants reach full capacity. And it is still expected that many European defense budgets will not reach the 2 percent of GDP threshold needed for a number of years—and even then, it is very possible that a number closer to 3 percent of GDP may be needed to meet the Russian threat.REF In the meantime, Europe faces a Russia that has roughly 2,000 NSNWs arrayed against a NATO NSNW arsenal of about 150 weapons.

Given the constraints on the United States (and its need to focus on deterring a war with China) and the increasing Russian threat, Europe must take primary responsibility for the conventional defense of Europe and deterrence of Russia—and it must do so quickly. Specifically, it must field most, if not all, conventional forces required to deny a Russian fait accompli in the Baltics, Finland, or Poland, while also leading efforts to arm Ukraine to defend itself. This is essential—and it is doable if European allies are willing. Indeed, history shows what U.S. allies are capable of. Now they must step up again.

However, all of this raises a singular important question:

If European NATO does not have the forces that are conventionally capable of deterring Russia, given Europe’s divestment of military combat power following the end of the Cold War and Russia’s putting its economy on wartime footing; and if NATO cannot rely on the type of nuclear advantage over Russia which it enjoyed during the early and mid–Cold War eras that enabled first “Massive Retaliation” and then the “Flexible Response” deterrence strategies; and if NATO does not have the magazine depth of long-range precision-fires and missile defense systems due to its self-imposed military drawdown and its support to Ukraine; and if the United States is increasingly husbanding its resources (particularly, its long-range precision-fires, attack submarines, sea and airlift, bombers, and its missile defense capabilities) to deter a potential conflict with China in the Western Pacific, then

What does Europe have in the immediate to five-year term to deter a Russia that could be putting upwards of an additional million men under arms, that has mobilized its economy and, in particular, its defense industrial base, that enjoys localized nuclear advantage, and is run by what can only be described as a quasi-fascist government that increasingly makes statements that hint or explicitly yearn for a type of bloodletting unseen since World War II?

This is the fundamental question facing European capitals today. To those who say that this is a compelling case for American retrenchment in Europe, they should be reminded that political leaders from President George W. Bush to Secretary of Defense Bob Gates to President Obama to President Trump to President Joe Biden have all told European nations that they must do more to defend their own region. Indeed, it is worth quoting Secretary of Defense Gates’s 2011 valedictory speech to NATO before retirement:

The blunt reality is that there will be dwindling appetite and patience in the U.S. Congress—and in the American body politic writ large—to expend increasingly precious funds on behalf of nations that are apparently unwilling to devote the necessary resources or make the necessary changes to be serious and capable partners in their own defense. Nations apparently willing and eager for American taxpayers to assume the growing security burden left by reductions in European defense budgets.

Indeed, if current trends in the decline of European defense capabilities are not halted and reversed, future U.S. political leaders—those for whom the Cold War was not the formative experience that it was for me—may not consider the return on America’s investment in NATO worth the cost.REF

What European NATO Members Must Do

Given that Russia will likely win the short-term race for production of militarily relevant capabilities and has already won the medium-term race for the NSNW advantage, NATO must think differently than in the past about how it will deter the authoritarians in Moscow. To wit, Europe should:

• Put its industry on a wartime footing. If the threat to Europe is as dire as many leaders in Finland, the Baltics, and Poland say it is, then leaders in all of NATO must re-industrialize their economies to produce massive quantities of munitions and military platforms—rapidly and at scale.
• Increase defense budgets, capabilities, and manpower to a level commensurate with the threat—immediately. The focus on 2 percent of GDP vs. 3 percent of GDP vs. Cold War–era funding levels can only be helpful to a certain point. European leaders must identify the defense requirements they believe they need to deter conventional aggression and, ultimately, nuclear coercion from Russia. This will likely require significantly larger militaries than have been seen in Europe since the fall of the Berlin Wall.
• Develop, in conjunction with Washington, a road map that identifies time frames and associated milestones to shift the primary burden for the conventional defense of Europe from American capabilities to European ones. Only by developing such a road map that compels capitals to commit resources and political capital can governments avoid the two-decades-long gap between the 2006 North Atlantic Council commitment to 2 percent of GDP defense budgets and the current crisis.

Conclusion

The United States takes the current security environment very seriously. It is committed to NATO and will remain so, but given the threat posed by China (whose economy in both real and relative terms dwarfs that of the Soviet Union at its peak), the United States must focus its attention and husband its resources to deter what could be a third world war that has its origins in the Western Pacific. China is the only actor that has the direct capability to overturn the free and open international system that has lifted billions out of poverty and promoted freedom worldwide. Moreover, the lack of a NATO-like alliance framework in the Western Pacific means that the United States must bear an even greater burden than it shouldered in the Cold War deterring the Soviet Union.

Therefore, Europe must take the primary responsibility for its conventional defense, especially by denying the aforementioned fait accompli in the East. Such a primary responsibility would include most, if not all, the conventional forces (naval platforms, long-range fires, missile defenses, land armies, and air power) necessary to deter and, if necessary, defeat the Russian military as the United States re-postures or divests its forces and capabilities to shore up defenses in the Pacific. The question then becomes what this looks like over the short term (one to two years) to mid term (three to five years).

The good news is that Europe’s wealth, demography, and technology levels dwarfs that of Russia. Europe—if it so chooses—is more than capable of fielding the credible defense necessary to deter even the most paranoid Russian autocrat from invading NATO territory.

Finally, Europe should understand that the United States views Europe with friendship and warmth, due to shared history, values, and interests—but increasingly stringent questioning of America’s commitment to NATO will be counterproductive. Indeed, to those Americans who remember that since the 1960s to this very day, the United States, which through its nuclear umbrella over NATO, has been willing to trade Washington, New York, and Chicago to defend Paris, Bonn, and later, Warsaw, such questioning of America’s commitment to NATO is repugnant, particularly as Americans do not enjoy the universal health care, free university, lavish unemployment benefits, and comfortable pensions that many Europeans do—in large part because the United States has underwritten European security since Europe largely disarmed at the end of the Cold War.

Despite all this, the United States remains committed to NATO and the defense of Europe.

Europeans must remain committed to the defense of Europe as well.

Robert Peters is Research Fellow for Nuclear Deterrence and Missile Defense in the Douglas and Sarah Allison Center for National Security at The Heritage Foundation.