By Eric Vandenbroeck and co-workers

To deter - or, if necessary, defeat - a Chinese invasion of Taiwan or a U.S. ally in the Indo-Pacific or a Russian attack on a NATO member, the United States must be prepared to deny its adversary a quick operational victory and either escalate to win or prevail in an extended war. A long war would create extraordinary demands on U.S. forces and burn through stockpiles of munitions, missiles, and air defenses. It would damage the U.S. economy, disrupting international trade and supply chains for critical goods and manufacturing inputs. The United States has begun to address some of these challenges, most notably by investing in the defense industrial base, but it has not done enough to prepare for protracted wars of attrition and less-piercing acts of aggression, such as a sustained blockade of Taiwan.

This lack of preparation could force Washington’s hand strategically. If the United States were less equipped than its adversary to fight a protracted conflict, it may feel the need to escalate early and dramatically - including potentially to use nuclear weapons - to curtail the conflict before it found itself stretched too thin. Washington relied on this escalation strategy to defend NATO during the Cold War out of necessity, but it has spent the decades since seeking to instead maintain conventional military superiority to place the burden of escalation on adversaries and avoid being boxed into its riskier previous approach. Today, preparing for protraction, arduous as it may be, is the only way to provide the White House with the full complement of options required for a great-power conflict.

Ukrainian service members under an anti-drone net in the Donetsk region, Ukraine, January 2026

 

Bargaining Phase

In Ukraine, the United States and Russia have each attempted to find limits on warfare that would achieve their desired objectives at the lowest possible cost. But neither entered the war with a clear, shared understanding of the other’s escalation thresholds. Only repeated probing, signaling, and adjustment by Washington and Moscow revealed how far each would be willing to go. This process of negotiation and contestation, rather than a fixed understanding of escalation thresholds, is likely to define any future great-power war.

In the run-up to Russia’s full-scale invasion, Washington and Moscow set the initial parameters of escalation. In December 2021, U.S. President Joe Biden said that putting U.S. troops on the ground to deter or defeat a Russian invasion was “not on the table.” Biden wanted to avoid a direct conflict that would come with the significant risk of nuclear escalation - or, as he put it, “World War III.” Putin, for his part, sought to deter direct intervention by third parties and prevent - or at least limit - support for Ukraine by the United States and its allies and partners. He warned “those who may be tempted to interfere” that “Russia will respond immediately, and the consequences will be such as you have never seen in your entire history.”

After the invasion, Washington and Moscow began a process of active probing and tacit bargaining. The Western alliance refused to heed Putin’s threat and continued providing significant economic and military assistance aimed at enabling Ukraine to preserve its sovereignty and retake lost territory. Biden made clear that the United States would defend “every inch of NATO territory,” warning Putin against expanding the conflict or interdicting military assistance provided through Poland and Romania. Moscow attempted to deter the United States from providing tanks, fighter jets, and long-range missiles that would enable Ukrainian strikes into Russian territory.

In most instances, concerns over escalation did not drive the Biden administration’s decisions about what assistance to provide. The United States wanted to give Ukraine the best chance to win the war, and with limited funding made available by Congress, Washington was skeptical of the military utility of high-end capabilities compared with more immediately useful alternatives such as air defenses and artillery rounds. The United States also had its own significant shortfalls in weapons stocks and needed to conserve them for other contingencies.

Russia did, however, find ways to shape the calculus in Washington and other NATO capitals by threatening escalation. Moscow tested what it could get away with short of a direct kinetic attack on NATO: jamming Western space capabilities, carrying out a sabotage campaign against infrastructure and logistics targets in Europe, conducting incursions into NATO airspace. Doing so allowed Russia to create a perception in Washington and European capitals that it might be willing to escalate. That concern, in turn, led the United States and its NATO allies to circumscribe their on-the-ground military and intelligence cooperation with Ukraine; delay the provision of long-range strike capabilities, such as the surface-to-surface ballistic Army Tactical Missile System (ATACMS); and put limits on the types of Ukrainian strikes into Russian territory they were willing to support or tolerate.

Yet over the course of the war, the United States and its allies and partners contravened nearly all the limits on Western assistance that Russia attempted to maintain. By probing Russia’s threats and gradually escalating its support for Ukraine’s forces, Washington was able to “salami slice” away Russia’s purported escalation thresholds, exposing most Russian threats as hollow. Meanwhile, Western intelligence sharing and operations support have enabled the Ukrainian military to use increasingly sophisticated capabilities to great effect.

Before the war, it would have been unthinkable that the United States would go as far as it has in facilitating long-range strikes into Russia without inviting a direct attack against NATO - and if the United States had taken that step in the first days after the invasion, it may have provoked such a response from Russia. But because the Biden administration escalated its assistance gradually, each step looked like an incremental change, not a dramatic jump. Before providing ATACMS, the United States sent Ukraine shorter-range missiles and one-way attack drones. Before enabling strikes on targets in Russia, the United States supported attacks against occupied Crimea.

To be sure, this strategy had its limitations. Although Ukraine has been able to prevent conquest and impose severe costs on Russia, it has little prospect of recovering full control of its entire territory any time soon. It is doubtful that any form of military assistance would have been a silver bullet, but in retrospect, Washington withheld some assistance and constrained Ukrainian operations longer than necessary: although earlier provision of ATACMS would not have made the difference that the most vocal advocates of their use suggest, the Ukrainian military could have employed them to target logistics hubs, airfields, and other high-value targets well behind the front in order to disrupt Russian operations and support Kyiv’s counteroffensives in 2023 and 2024.

In the event of a conflict with Russia or China, bargaining over escalation thresholds will again prove critical in determining the costs both sides will endure - and in determining which side emerges victorious. Unlike in Ukraine, a war with Russia or China will likely invoke Article 5 of the North Atlantic Treaty, the Taiwan Relations Act, or a bilateral mutual defense treaty, meaning that direct U.S. involvement will not represent the most consequential threshold. But even then, the parties will bargain over significant conflict thresholds, be they strikes on national territory, attacks on critical infrastructure, or nuclear escalation. Washington must be prepared to probe, signal, and maneuver along the escalation spectrum - sometimes restraining itself, sometimes escalating deliberately - to establish advantageous limits that provide the United States the military freedom to achieve its desired objectives while minimizing the cost and risk.

Beyond deterring nuclear attack, the United States must be prepared to set limits on conflict. Conflict in space and cyberspace, for example, may be unavoidable, but Washington should nonetheless seek to spare its most important assets in space, including those that facilitate nuclear command and control, and prevent cyberattacks that could permanently damage critical infrastructure, such as the power grid or the financial system, by threatening severe consequences while withholding commensurate attacks. On land, Russia and China will hope to protect their own territory so that they can strike and resupply with impunity. The United States must be prepared to escalate and probe, seeking to conduct select strikes on mainland targets from which Moscow and Beijing are likely to launch aggressive attacks. Washington should still exercise restraint in the intensity of strikes on these mainland targets to deter large-scale retaliatory strikes. Precisely because any limits will emerge through tacit bargaining, it will be impossible to establish these thresholds in advance of a potential conflict. Washington needs approaches to warfare designed as much for probing as for military effect.

Firing toward Russian troops in the Donetsk region, Ukraine, January 2026

 

Agree To Disagree

As much as the war has showcased NATO’s capacity to come together in support of a threatened partner, it has also tested Washington’s ability to manage a coalition during a high-stakes conflict and made clear the limits of Washington’s control of escalation management. Ukraine has demonstrated a higher tolerance for escalation risks, particularly those associated with strikes on Russian territory, than the United States and some of its NATO allies have. It has also acted without U.S. input, at times working at cross-purposes with the United States. These dynamics would exist even if Washington were fighting alongside treaty allies, but they are particularly challenging when the United States must come to the aid of quasi-allies such as Ukraine and, in the event of a conflict with China, Taiwan.

Ukraine’s forces are fighting for the survival of their country, with military, intelligence, and other assistance from the United States and other partners. Washington can decide the scope and scale of the security assistance it provides and include end-use restrictions on how the Ukrainian armed forces employ U.S. weapons. But since the United States is not a combatant, key tactical, operational, and strategic choices ultimately lie with Kyiv.

The United States and Ukraine have at several points diverged in their assessments of the risk-reward calculus of strikes on targets in Russia. Whereas Washington counseled caution, particularly in using U.S. military materiel to hit Russian territory, and encouraged a focus on operations that would degrade Russia’s occupying forces or otherwise disrupt Russian military operations, Kyiv consistently sought permission for deeper strikes against a broader range of targets, seeking to weaken Russia’s military operations, impose economic and political costs on Putin’s regime, and bolster Ukrainian morale. Although Ukraine generally honored the limits the United States placed on it, it conducted the invasion of the Kursk region using American equipment without Washington’s approval or coordination. Kyiv also used its own drone capabilities, over which Western governments could exert less control, to strike critical infrastructure and targets thought to have symbolic importance for Moscow. This divergence is hardly surprising; Ukraine was not concerned about provoking a Russian attack on NATO. If anything, drawing the West directly into the war would be a boon for Kyiv.

But U.S. allies and partners will not always be more risk-tolerant than Washington. If Russia had employed nuclear weapons against Ukraine and Kyiv feared that follow-on strikes might devastate its armed forces or kill hundreds of thousands of civilians in population centers, Ukraine, in the nuclear cross hairs with much to lose, might have proved less risk tolerant. The United States, by contrast, might have felt that with the norm against nuclear use already shattered, its leadership of the global nuclear order was at stake. As a result, Washington might have been willing to take on more risk, including potentially entering the conflict directly.

The United States should recognize the inevitability of wartime friction with its coalition partners and plan accordingly. The need for such planning is particularly acute with respect to quasi-allies such as Ukraine and Taiwan, for which the United States has devised no mature processes for peacetime planning and wartime combined operations. But even when the United States comes to the defense of a treaty ally and can assume more direct control, national interests and leaders’ political incentives will invariably diverge. And because of the proliferation of long-range weapons systems, U.S. allies will be independently capable of inflicting meaningful damage on adversaries. Washington and its partners can reduce friction by seeking alignment ahead of time on questions of military strategy and escalation management.

With its treaty allies, Washington should revisit joint military plans and test command structures by conducting realistic war games and exercises. With Taipei, it needs to develop a common understanding of how command and control would work if the United States were to intervene to defend Taiwan, using war games, alongside official and unofficial dialogues, to surface and resolve disagreements over operational risk tolerance, escalation management, and war termination. And with Ukraine, although Kyiv and Washington already cooperate successfully, the United States should take advantage of any cease-fire to jointly plan for how to fight renewed Russian aggression, especially if Washington extends a security guarantee and NATO allies deploy forces in Ukrainian territory.

Repairing a pipe at Darnytsia Thermal Power Plant in Kyiv, February 2026

 

The Fires Next Time

The war in Ukraine has been a tragic and costly tutorial in twenty-­first-century conflict. Both sides have mobilized and reshaped their societies, attacked a variety of important targets, and suffered devastating casualties. The great-power wars of the future could be even more destructive.

Yet these wars are likely to remain limited rather than total, because all sides want to achieve their objectives while containing costs and avoiding nuclear catastrophe. This challenge is not novel; it was a hallmark of the Cold War. But the war in Ukraine is a harbinger of a new era of limited war. Preparing for it demands a theory of victory rooted in favorable escalation management, refined through constant interrogation of escalation thresholds, and translated into refreshed U.S. strategies, plans, and capabilities that expand options available to the president. By showing that it can come to the defense of allies and partners at an acceptable risk level, the United States will strengthen deterrence by making its intervention more credible in the eyes of its adversaries.

Escalation management is not only about avoiding nuclear war. The United States must also shape how its adversaries fight under the nuclear shadow by threatening higher costs and greater risk if they cross certain thresholds. Future wars between the United States and Russia or China are likely to extend into their respective homelands and into space and cyberspace, and Washington will need to figure out what limits it ought to maintain on conflicts in those domains.

Planning is crucial. But wars never unfold exactly as envisioned. The United States must hone its skills in probing and tacit negotiation. Adversaries will try to constrain and deter U.S. actions while seeing what they can get away with under U.S.-imposed limits by testing the seriousness of American threats to escalate. At times, the United States will need to intentionally escalate to an advantageous position. At other times, slow escalation or self-restraint may be the best way to discourage escalation by adversaries. In every case, policymakers must ensure that the risks Washington takes are calculated and aimed at bringing a potential conflict to an acceptable close. And in every case, Washington should make the necessary investments in its strategic stockpiles, its defense industrial base, and its national resilience against cyberattacks and economic shocks to prevail in a protracted conflict. Such careful calibration will require intense coordination with coalition partners fighting alongside the United States. Whenever possible, Washington and its partners should carry out joint exercises designed to align expectations in advance of a conflict. But exquisite coordination on strategic messaging and signaling in the midst of hostilities is also essential, particularly with Taiwan, where restrictions on contact between Washington and Taipei constrain joint peacetime contingency planning and operational integration.

Above all, the war in Ukraine has shown the United States that it needs a new theory of victory for wars that feature great-power aggressors attacking U.S. allies or quasi-allies. Only by linking credible threats, calibrating escalation, and managing coalition partnerships can Washington and its allies prevail in wars that remain limited in intensity and scope but take a massive toll.

 

 

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