By Eric Vandenbroeck and co-workers

The Real Risks of Escalation in Ukraine

As U.S. President Joe Biden’s national security team prepares to depart, one of its chief foreign policy strategies is facing a withering assault. A growing chorus of critics argues that Ukraine’s current dire situation is partly the result of Biden’s timid approach to helping Kyiv defend itself against Russia’s invasion. Excessively worried about triggering World War III, the administration shied away from swift and major weapons transfers that might have altered the war’s course at key junctures. Setting aside debates about weapons stockpiles, logistics, training, and the battlefield effect of different weapons systems, the core claim is that Biden’s team needlessly allowed itself to be deterred from bolder action by Russian President Vladimir Putin’s threats.

These critics are wrong. Their conclusion that the Biden administration overestimated the risk of escalation underestimates how hard it is to navigate redlines in a crisis and assess an enemy’s risk calculus. Whether intentionally or not, the administration’s approach resembled salami slicing, a common strategy whereby an actor seeks to undermine an adversary’s redlines in such small increments that any substantial retaliation is rendered unreasonable. International relations scholars typically view this tactic as one employed by revisionist powers, such as China, when it pushes against maritime boundaries in the South China Sea, or Russia, when in 2014 it sent heavily armed commandos without identifying insignia—so-called “little green men”—to seize Crimea from Ukraine. But in this case, Washington deployed the strategy to counter a highly motivated revisionist adversary. And it worked.

The irony is that Washington’s salami-slicing strategy has now become a victim of its success. The absence of major escalations in Ukraine has led critics to argue that the Biden administration should have been bolder and abandoned the very gradualism that likely helped prevent escalation in the first place. Learning the right lessons from this case is essential for navigating future crises with revisionist powers.

 

Toeing the Line

A core theme running through many critiques of Biden’s Ukraine policy is that senior officials have been too credulous of Russia’s stated redlines. Since the start of the war, Putin has issued numerous warnings aimed at deterring Western intervention. They ranged from generic threats related to the provision of weapons to Ukraine to more specific threats about how Moscow would respond if Western countries supplied long-range missiles. At times, Putin made veiled threats to use nuclear weapons if his redlines were crossed.

Although Biden’s critics believe these threats were bluffs, they are rarely explicit about what Putin’s actual redlines might be, if there are any. Instead, they simply suggest that because the United States has routinely crossed the lines Putin established without sparking major escalation, going much further faster would have been justified. As Adam Kinzinger, a former Republican congressman from Illinois, and Ben Hodges, who served as commanding general of U.S. Army Europe, wrote in a May 2024 op-ed for CNN: “In almost every one of these cases, Russia threatened escalation, an attack on NATO or the use of nuclear weapons. Each time, the bluff was called, and Ukraine was able to better defend its territory. . . . Imagine if we had provided Ukraine with all of the . . . weapons [Ukraine requested] from the start? . . . The war might have ended.”

The problem is that redlines and escalation thresholds are not inscribed on stone tablets. They are socially constructed moving targets that emerge endogenously during conflicts. Something that represents a redline at a particular moment may not function as one in perpetuity.

History offers numerous examples of redlines’ fluidity. Operation Cyclone, the covert program the United States ran from 1979 to 1992 to aid the mujahideen fighting the Soviet-backed Afghan government, is one. Early in President Ronald Reagan’s administration, U.S. officials were reluctant to give the rebels Stinger missiles capable of shooting down Soviet helicopters. By the middle of the 1980s, the Reagan administration had relaxed this restriction as escalation calculations changed. Other apparent redlines, including a prohibition on supporting direct raids into the Soviet Union, remained in place.

In the case of Ukraine, actions that might have been viewed early in the war as crossing a genuine redline, such as openly supplying weapons that could reach into Russian territory, likely became less taboo over time as the context evolved. It is worth remembering that Biden eased restrictions on Ukraine’s ability to fire ATACMS, long-range precision missiles, directly into Russia only after Ukraine was already operating on Russian soil and after the discovery that North Korean troops were being deployed to the front in significant numbers.

In the rare cases when critics explicitly address Russia’s redlines, they define them exceedingly narrowly. The basic idea is that open and direct NATO participation in the conflict is the only thing that is truly off-limits for Putin. NATO should pursue a strategy of going as far as possible in Ukraine without plainly crossing Russia’s redlines—meaning refusing to openly attack Russian forces or send combat units into the country. The United States prevailed in the gravest crises of the Cold War by using this approach.

If the war between Russia and Ukraine closely resembled Cold War–era cases, as some critics imply, they might indeed offer ready-made blueprints with respect to Putin’s real redlines. But these analogies and precedents are imperfect and conflicting. Altman is right, for example, that the Soviets generally tolerated U.S. assistance to the mujahideen. The problem with using that example to argue that the West has been too cautious in Ukraine is that U.S. support in Afghanistan in the 1980s was designed to be plausibly deniable. The military aid the United States has offered to Ukraine, by contrast, is a highly visible affair.

Moreover, in cases such as Afghanistan’s, the recipients of Washington’s support were insurgents. The same was true of numerous “rollback” operations the United States undertook early in the Cold War to undermine Soviet influence in Eastern Europe. By contrast, in Ukraine, the United States is openly backing a sovereign government against unprovoked aggression. International law is clearly on its side. This would seem to give Washington the latitude to provide Kyiv with whatever it asks for. Yet there is little precedent from the Cold War of one superpower supplying a smaller state under attack with the physical means to strike the sovereign territory of a nuclear-armed aggressor with which it shares a large contiguous border. Toward the end of Biden’s time in office, this is exactly what has been under consideration. Moreover, the stakes in Ukraine for Moscow appear far higher than in Cold War conflicts such as Korea and Vietnam, faraway proxy fights to which the Kremlin devoted far fewer resources. Thus, Cold War history offered only an ambiguous guide to discerning where Putin’s true redlines were.

After a Russian missile strike in central Kyiv, in December 2024

 

Survival Tactics

Along with overrating how reliably the West can divine Putin’s redlines, critics downplay another significant factor that differentiates the current conflict from Cold War precedents and changes Moscow’s calculus around escalation: the risks to the regime’s survival. Surprising military setbacks, especially early in the war, had raised real questions about Putin’s grip on power.

As Ukraine’s stunning counteroffensives in Kharkiv and Kherson in the fall of 2022 got underway, Ukrainian President Volodymyr Zelensky continued to call on Washington to provide Kyiv with longer-range missiles. According to reporting by Bob Woodward in his October 2024 book War, however, during that period, Washington received “highly sensitive, credible” intelligence based on “conversations inside the Kremlin” that Putin “was seriously considering using a tactical nuclear weapon.” If Russia’s 30,000 troops in Kherson faced encirclement, U.S. intelligence—its credibility riding high after its accurate forecast of the initial 2022 invasion—put the odds at 50 percent that Putin would use nonstrategic nuclear weapons to avoid the loss of troops. Analysts outside the government identified additional plausible and dangerous scenarios for nuclear escalation, including the launch of a “demonstration shot” over the Black Sea. Florida Senator Marco Rubio raised the prospect that Putin could order a strike on transit hubs for supplies from the West.

The administration, clearly viewing the threat of escalation as credible, went into overdrive to deter Russia. It issued private messages to Putin and his national security team, scrambled to get leaders around the world to issue public warnings against the use of nuclear weapons, and developed potential responses to their deployment. The administration’s reluctance to go all in—out of a fear that Russia may escalate in response to catastrophic battlefield losses—is just what has frustrated critics. It appears to consign Ukraine to an attrition war in which it faces insurmountable odds. How can Ukraine win if its hands are tied, especially when it has the invading Russians on the ropes? After all, the defeat of an invading force is not necessarily an existential threat to the invader itself. Isn’t Russia invading a neighbor and deterring the United States from aiding its victim merely a recipe for future nuclear-fueled revisionism?

The problem is that escalation becomes credible when the stakes are existential, and threats can be “existential” for a personalist dictator like Putin even if not for the country he runs. When a leader’s grip on power is under threat and escalating a war promises to save his position, a thoroughly rational dictator may choose to gamble for his resurrection—say, by lobbing a low-yield nuclear missile at a target in Ukraine. Even if the risks outweigh the benefits for the Russian people, the bet might pan out for Putin himself. This dynamic is especially relevant for despots who do not intend to exit the scene peacefully when their tenure is up. International relations scholars Giacomo Chiozza and Hein Goemans have found that the threat of exile, imprisonment, or death can cause leaders to take risks they might otherwise not. 

Many observers saw the threat in these terms. In October 2022, the retired general and former CIA director David Petraeus described Putin as “desperate.” Rubio warned that Putin’s desperation might lead him to use nuclear weapons: “Certainly, the risk is probably higher today than it was a month ago.” Similar concerns persisted long after the Ukrainian counteroffensive ended. In War, Woodward quotes Director of National Intelligence Avril Haines as stating in the spring of 2024 that “between the United States and Russia, we have over 90 percent of the world’s nuclear weapons. . . . You do not want a country that has got that kind of a stockpile of nuclear weapons to feel as if it’s slipping.”

Risky gambles for self-preservation become even more plausible if leaders receive warped information about the scale of the threats they face. In March 2022, the White House said it had credible intelligence that Putin was getting hyped threat assessments from his advisers about the West’s intentions. And it does not require privileged access to see that information has not flowed smoothly through Moscow’s corridors of power. After all, the invasion itself was premised on profoundly flawed assessments of the situation in Ukraine.

Those in Washington managing the delicate dance around escalation had to reckon with the possibility that any signals they sent would suffer heavy distortion en route to the Kremlin’s decider-in-chief. To be sure, fears of escalation related to regime survival have ebbed as Russia’s position stabilized. Still, navigating Putin’s many redlines has remained a challenge throughout the war.

 

Cutting Edge

In Arms and Influence, the economist and Nobel laureate Thomas Schelling describes “salami tactics” as a process of gradually shifting the status quo. “One can begin his intrusion on a scale too small to provoke a reaction,” Schelling writes, “and increase it by imperceptible degrees, never quite presenting a sudden, dramatic challenge that would invoke the committed response.” The concept is usually applied to aggressors trying to make small gains while avoiding direct conflict. In practice, the strategy has much broader applicability, including for defenders of a status quo seeking to manage escalation.

The concept of salami tactics essentially captures the Biden administration’s strategy. And it was a reasonable response, given the risks inherent in a situation in which Putin plausibly could have seen the stakes of major battlefield losses in Ukraine as existential and in which there was a lack of ready-made analogies to identify clear redlines. Gradualism in the provision of military aid enabled Russia to slowly adjust to a new status quo in which Ukraine received increasingly capable fighting platforms and munitions. Deliberately pushing boundaries in such a way that no single decision by Washington warranted dramatic escalation by Russia (for example, tactical nuclear weapons use) allowed weapons and aid to accumulate.

Psychology also lent credence to a salami-slicing approach. Decades of research show that people are far more willing to run risks to avoid losses than to make comparable gains. The greater the speed and magnitude of loss, the higher a person’s acceptance of risk; several recent studies have found that individuals show a greater appetite for risk when they suffer large losses quickly. Putin’s threats to attack NATO may well be “dubious” from the standpoint of a rational leader, as Hal Brands argued in a Bloomberg column in May 2024, because such an attack “would change [the] war fundamentally.” But leaders facing the prospect of high losses, especially when setbacks are already mounting rapidly, sometimes do irrational-seeming things.

Salami tactics were strategically wise, given the pervasive uncertainty about where Putin’s genuine redlines were—a degree of uncertainty that defenders of Biden’s policy argue warranted such a trial and error approach. But such tactics would also have been useful in instances when the Biden administration believed that it was getting close to a real redline, such as the decisions to allow Ukraine to strike targets in Russia with HIMARS rocket systems near Kharkiv in May, followed by the loosening of restrictions on ATACMS in November. The very act of subtly altering the status quo creates ambiguity about whether the United States has indeed stepped over a redline and, over time, can even shift the status quo well beyond what Putin would have tolerated had the same aid been provided all at once.

To be sure, Putin has escalated in important ways over the course of the conflict. In November, he fired an intermediate-range nuclear-capable ballistic missile at Dnipro. The deployment of at least 10,000 North Korean troops to help Russia, in some cases fighting Ukrainian troops directly, was another escalation. The core question for evaluating Biden’s approach is not whether some escalation has occurred. It has. Instead, the real question is whether it could have been much worse. There are many reasons to suspect it might have been.

 

Measuring Success

One major lesson to draw from the Biden administration’s Ukraine policy is that measuring success is more complicated than meets the eye. If the most important metric is providing Ukraine with the means to recapture all of its sovereign territory, Biden’s policy was a partial failure. Although Western aid has enabled Ukraine to put up significant resistance, the results remain indecisive. If the measure of success is whether the United States’ policy avoided starting another world war, however, the Biden administration’s approach fared better, although even here it is hard to know whether that same outcome could have been reached with more a rapid provision of aid.

But there is another way to measure success that is rarely discussed: namely, whether Biden’s team effectively defeated Putin’s attempts to redefine thresholds for escalation that would have set a dangerous precedent for the future. This conflict is not only about Ukraine or the rules-based international order. It is also about how the United States and the West more broadly should think about escalation thresholds in a new era of great-power rivalry that often bears little resemblance to the Cold War. From the beginning, Putin tried to enforce redlines that aimed to deter status-quo parties—the United States and NATO allies—from assisting Ukraine. Slowly, carefully, and with circumspection, Biden succeeded in eroding and undermining those redlines. Salami tactics did not offer the ringing victories that many hoped for, but they did provide important pushback.

These dynamics around navigating escalation thresholds also have implications for the competition between the United States and China. The risk of escalation during any conflict over Taiwan would depend on a variety of factors, including Chinese leader Xi Jinping’s prewar expectations about victory and whether a loss in Taiwan would threaten the survival of the Chinese Communist Party’s rule. Obtaining credible intelligence about each of these factors would be essential for figuring out how far and how fast the United States would be able to go in aiding Taiwan. The greater the gap between how Xi believed the war would unfold and how it unfolded—or the greater the risk it posed to his ability to hang on to power—the more powerful the argument in favor of salami-style tactics.

Additionally, the use of Cold War-era analogies—or even analogies from the war in Ukraine—might go out the window if the United States decided to deploy troops to defend Taiwan. There is no historical case of two nuclear-armed great powers engaged in direct combat, something policymakers and analysts worried about during the Cold War but which never came to pass. In such a scenario, reading and responding to the escalation thresholds that would govern how the conflict played out will require a great deal of communication, learning, and potentially salami-slicing.

 

Cutting Edge

In Arms and Influence, the economist and Nobel laureate Thomas Schelling describes “salami tactics” as a process of gradually shifting the status quo. “One can begin his intrusion on a scale too small to provoke a reaction,” Schelling writes, “and increase it by imperceptible degrees, never quite presenting a sudden, dramatic challenge that would invoke the committed response.” The concept is usually applied to aggressors trying to make small gains while avoiding direct conflict. In practice, the strategy has much broader applicability, including for defenders of a status quo seeking to manage escalation.

The concept of salami tactics essentially captures the Biden administration’s strategy. And it was a reasonable response, given the risks inherent in a situation in which Putin plausibly could have seen the stakes of major battlefield losses in Ukraine as existential and in which there was a lack of ready-made analogies to identify clear redlines. Gradualism in the provision of military aid enabled Russia to slowly adjust to a new status quo in which Ukraine received increasingly capable fighting platforms and munitions. Deliberately pushing boundaries in such a way that no single decision by Washington warranted dramatic escalation by Russia (for example, tactical nuclear weapons use) allowed weapons and aid to accumulate.

Psychology also lent credence to a salami-slicing approach. Decades of research show that people are far more willing to run risks to avoid losses than to make comparable gains. The greater the speed and magnitude of loss, the higher a person’s acceptance of risk; several recent studies have found that individuals show a greater appetite for risk when they suffer large losses quickly. Putin’s threats to attack NATO may well be “dubious” from the standpoint of a rational leader, as Hal Brands argued in a Bloomberg column in May 2024, because such an attack “would change [the] war fundamentally.” But leaders facing the prospect of high losses, especially when setbacks are already mounting rapidly, sometimes do irrational-seeming things.

Salami tactics were strategically wise, given the pervasive uncertainty about where Putin’s genuine redlines were—a degree of uncertainty that defenders of Biden’s policy argue warranted such a trial and error approach. But such tactics would also have been useful in instances when the Biden administration believed that it was getting close to a real redline, such as the decisions to allow Ukraine to strike targets in Russia with HIMARS rocket systems near Kharkiv in May, followed by the loosening of restrictions on ATACMS in November. The very act of subtly altering the status quo creates ambiguity about whether the United States has indeed stepped over a redline and, over time, can even shift the status quo well beyond what Putin would have tolerated had the same aid been provided all at once.

To be sure, Putin has escalated in important ways over the course of the conflict. In November, he fired an intermediate-range nuclear-capable ballistic missile at Dnipro. The deployment of at least 10,000 North Korean troops to help Russia, in some cases fighting Ukrainian troops directly, was another escalation. The core question for evaluating Biden’s approach is not whether some escalation has occurred. It has. Instead, the real question is whether it could have been much worse. There are many reasons to suspect it might have been.

 

Measuring Success

One major lesson to draw from the Biden administration’s Ukraine policy is that measuring success is more complicated than meets the eye. If the most important metric is providing Ukraine with the means to recapture all of its sovereign territory, Biden’s policy was a partial failure. Although Western aid has enabled Ukraine to put up significant resistance, the results remain indecisive. If the measure of success is whether the United States’ policy avoided starting another world war, however, the Biden administration’s approach fared better, although even here it is hard to know whether that same outcome could have been reached with more a rapid provision of aid.

But there is another way to measure success that is rarely discussed: namely, whether Biden’s team effectively defeated Putin’s attempts to redefine thresholds for escalation that would have set a dangerous precedent for the future. This conflict is not only about Ukraine or the rules-based international order. It is also about how the United States and the West more broadly should think about escalation thresholds in a new era of great-power rivalry that often bears little resemblance to the Cold War. From the beginning, Putin tried to enforce redlines that aimed to deter status-quo parties—the United States and NATO allies—from assisting Ukraine. Slowly, carefully, and with circumspection, Biden succeeded in eroding and undermining those redlines. Salami tactics did not offer the ringing victories that many hoped for, but they did provide important pushback.

These dynamics around navigating escalation thresholds also have implications for the competition between the United States and China. The risk of escalation during any conflict over Taiwan would depend on a variety of factors, including Chinese leader Xi Jinping’s prewar expectations of victory and whether a loss in Taiwan would threaten the survival of the Chinese Communist Party’s rule. Obtaining credible intelligence about each of these factors would be essential for figuring out how far and how fast the United States would be able to go in aiding Taiwan. The greater the gap between how Xi believed the war would unfold and how it unfolded—or the greater the risk it posed to his ability to hang on to power—the more powerful the argument in favor of salami-style tactics.

Additionally, the use of Cold War-era analogies—or even analogies from the war in Ukraine—might go out the window if the United States decided to deploy troops to defend Taiwan. There is no historical case of two nuclear-armed great powers engaged in direct combat, something policymakers and analysts worried about during the Cold War but which never came to pass. In such a scenario, reading and responding to the escalation thresholds that would govern how the conflict played out will require a great deal of communication, learning, and potentially salami slicing.

 

 

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