How Russia Stopped Ukraine’s Momentum
A Deep Defense Is Hard to Beat
Many held high hopes for Ukraine’s 2023 summer offensive. Previous Ukrainian successes at Kyiv, Kharkiv, and Kherson encouraged expectations that a new effort, reinforced with new Western equipment and training, might rupture Russian defenses on a larger scale and sever the Russian land bridge to Crimea. If it did, the thinking went, the resulting threat to Crimea might persuade Putin to end the war.
The results fell far short of such hopes. Although the summer brought some Ukrainian successes (especially against Russian warships in the Black Sea), there was no breakthrough on land. Limited advances were bought at great cost and have now been significantly offset by Russian advances elsewhere on the battlefield. It is now clear that the offensive failed.
Why? And what does this mean for the future of the Ukraine War and the future of warfare more broadly? Robust answers will require data and evidence that are not yet publicly available. But the best answer for now lies in the way the two sides, and especially the Russian defenders, used their available forces. By late spring, the Russians had adopted the kind of deep, prepared defenses that have been very difficult for attackers to break through for more than the last century of combat experience. Breakthrough has been—and still is—possible in land warfare. But this has long required permissive conditions that are now absent in Ukraine: a defender, in this case Russia, whose dispositions are shallow, forward, ill prepared, or logistically unsupported or whose troops are unmotivated and unwilling to defend their positions. That was true of Russian forces in Kyiv, Kharkiv, and Kherson in 2022. It is no longer the case.
The implications of this for Ukraine are grim. Without an offensive breakthrough, success in land warfare becomes an attrition struggle. A favorable outcome for Ukraine in a war of attrition is not impossible, but it will require its forces to outlast a numerically superior foe in what could become a very long war.
QUESTIONABLE EXPLANATIONS
Some blame the United States for Ukraine’s failed offensive. Not all of Kyiv’s requests for assistance were granted. For example, if the United States had provided F-16 fighters, the long-range missiles known as ATACMS, or Abrams tanks sooner and in larger quantity, they argue, Ukraine could have broken through. More and better equipment always helps, so surely the offensive would have made more progress with more advanced weapons. But technology is rarely decisive in land warfare, and none of these weapons were likely to transform the 2023 offensive.
The F-16, for example, is a 46-year-old platform that would not be survivable in Ukraine’s air defense environment. The United States and NATO are replacing it with more advanced F-35 fighter jets precisely because it is too vulnerable. Although the F-16 has been modernized since its introduction in 1978 and it would be an upgrade to Ukraine’s even older and less survivable Soviet-era MIG-29s, a fleet of F-16s would not give Ukraine air superiority in any way that could create a breakthrough on the ground.
ATACMS missiles would have enabled Ukraine to strike deeper targets, especially in Russian-held Crimea, and this would have reduced the efficiency of the Russian logistical system in particular. But all weapons have countermeasures, and the Russians have already proved adept at countering the GPS guidance that ATACMS uses to hit its targets. The shorter-range HIMARS missile system was highly effective for Ukraine when first introduced to the war in 2022 but is now much less so, in part because the Russians have reduced their reliance on large supply nodes within the weapon’s reach but also because they have learned to jam the GPS signals that both missile systems use for guidance.
War-winning weapons are very rare in land warfare.
American Abrams tanks are far superior to Ukraine’s fleet of mostly Soviet-era T-64s and T-72s. But so are the German Leopard 2 tanks that Ukraine used in the summer offensive. The Leopard 2s performed well but were hardly invulnerable superweapons. Of the fewer than 100 Leopard 2s in Ukrainian service, at least 26 have been knocked out; others cannot be used because of repair and maintenance issues. Like all tanks, the Leopard 2 and Abrams depend on tight combined-arms coordination with infantry, artillery, and engineers at scale to survive on the battlefield, and they require an extensive support infrastructure to sustain themselves in combat. Ukraine proved unable to provide these in 2023. Weakly supported Leopard 2s led the initial summer assaults but made little headway. More such advanced tanks would have helped, but the offensive offers little evidence that better tanks would have been decisive.
Others trace the problem to a broader military revolution in which new technology is held to be making the battlefield too lethal for successful offensive maneuvers, regardless of F-16 fighters, ATACMS missiles, or Abrams tanks. Drones, satellite surveillance, and precision weapons are the technologies that most military revolution theorists now emphasize. Yet all were present for Ukraine’s offensive successes in 2022 as well as its offensive failure in 2023. And the realized lethality of these new systems in actual use has not been radically greater than that of previous generations of weapons in more than a century of great-power combat experience. The Ukraine war experience shows little evidence of any new age of technologically determined defense dominance.
Still others emphasize training and strategic decision-making. The brigades that Ukraine committed to the summer offensive were mostly inexperienced formations that received just five weeks of Western training before the operation. By contrast, British infantry in World War II were given 22 weeks of instruction, then further training in their combat units, and were only then committed to combat. Five weeks is not enough time to master the complexities of modern battle. Some U.S. officers also believe that the Ukrainian general staff diluted the country’s combat power by dividing its efforts across three fronts rather than a single axis, leaving the troops on each front too weak to make headway. Between the diffusion of effort and the limited training of key units, in this view, the Ukrainians were left without the ability to use the assets at their disposal effectively.
INTRINSICALLY DIFFICULT
There is some truth to the training and decision-making arguments. As I argued in a previous Foreign Affairs essay, variations in how forces are used have usually been more important than variations in materiel, so explanations based on force employment have considerable face validity. But these arguments imply that if Ukrainian forces had been better trained and focused, they would have broken through in 2023. Perhaps. But while the Russians have shown little skill or motivation on the offensive, they are now competent defenders. Russian defenses in 2023 were deep, well prepared, fronted by extensive minefields, backed by mobile reserves, and garrisoned by troops who fought hard when attacked. Breakthroughs of defenses like these have historically proven very difficult even for well-trained attackers with a focused main effort.
The German Wehrmacht of World War II is commonly considered among the modern era’s most proficient armies at the tactical and operational levels of war. Yet the German breakthrough attempt at Kursk in southwestern Russia in 1943 failed when confronted with deep, well-prepared Soviet defenses. Erwin Rommel’s German Afrika Corps failed to break through deep Allied defenses at Tobruk in Libya in 1941 despite its air superiority and a major advantage in tanks, and Rommel failed to break through deep Allied defenses at Alam el Halfa in Egypt in 1942.
In fact, it has been very rare historically for attackers to break through defenses of this kind. During World War II, Allied armies with air superiority and crushing numerical advantages still failed against such defenses in Operations Epsom, Goodwood, and Market Garden and in the battles of Monte Cassino, the Siegfried Line, and Villers-Bocage in 1944–45. Nor did this pattern end in 1945. Iraqi armored offensives became bogged down against even moderately deep Iranian defenses in the siege of Abadan in 1980–81, and Iranian offensives failed to penetrate Iraqi defenses in depth at Basra in 1987. More recently, the 1999 battle of Tsorona between Ethiopia and Eritrea and the Israeli invasion of southern Lebanon in 2006 showed a similar pattern, with mechanized offensives making slow progress when they encountered deep, prepared defenses.
Offensive maneuver is not dead. But it has never been easy.
Offensive breakthroughs do happen. But they typically require a combination of offensive skill and a permissive environment created by shallow, forward defensive deployments or unmotivated or logistically unsupported defenders or both. The German invasion of France in 1940 knocked France out of the war in a month, and the German invasion of the Soviet Union in 1941 advanced to the gates of Moscow in a season, but both offensives were enabled by shallow, ill-prepared defenses that committed too much of their combat power forward where it could be pinned down, away from the point of attack. The American offensive in Operation Cobra in Normandy in 1944 broke through an atypically shallow, forward German defense. The Israeli offensive in the 1967 War broke through Egyptian defenses in the Sinai in less than six days, but this was enabled by poor Egyptian combat preparations and motivation.
The American offensive in Operation Desert Storm of 1991 reconquered Kuwait in 100 hours, but this was enabled by fatally flawed Iraqi fighting positions and the limited skills of Iraqi soldiers. Similarly, Ukrainian offensives at Kyiv and Kharkiv in 2022 broke through shallow, overextended Russian defenses, and the Ukrainian offensive at Kherson in 2022 overwhelmed a logistically unsustainable Russian defense that was isolated on the western side of the Dnieper River.
By 2023, however, the Russians had adapted and deployed a more orthodox defense in depth without the geographical vulnerability that had undermined them at Kherson. And these better-designed defenses were garrisoned by troops who fought. Russia’s poor performance and weak combat motivation in 2022 had led many to expect Russian incompetence or cowardice or both in 2023, but the Russians had learned enough from their failures to present a much tougher target by then. Perhaps an attacker with U.S.-level skills and training could have broken through, as those who emphasize training or operational decision-making tend to imply. But a large advantage in skill and motivation is needed to breach defenses like these. Ukraine did not enjoy this in 2023, and it is unclear whether even American troops would have the skill differential sufficient for a task this difficult.
QUALITY VERSUS QUANTITY
The resilience of deep, prepared defenses in modern warfare will make it very hard for Ukraine to achieve a decisive breakthrough any time soon. For more than a century, this has required conditions that seem unlikely for Ukraine at this point. The commander in chief of the Ukrainian armed forces, General Valery Zaluzhnyi, has characterized the war as stalemated but believes that new technology can enable a Ukrainian breakthrough. He’s right on the first point, but probably not the second. War-winning weapons are very rare in land warfare. The difficulty of offensive maneuver in 2023 was not a product of any radical new technology, and it is unlikely that any radical new technology will overturn it. The enemy’s adaptation and the ubiquity of cover and concealment on land limit the ability of new weapons to punch through robust defenses, and Russia’s defenses are now quite robust. Ukraine’s prognosis depends heavily on the future of Western assistance, but even with continued aid, the conflict is likely to remain an attritional war of position for a long time to come, absent a collapse in Russian will to fight or a coup in Moscow. Success for Ukraine will thus require patience for a long, hard war on the part of both Ukraine and its Western allies.
What does this mean for the future of warfare more broadly? Offensive maneuver is not dead. But it has never been easy. It typically requires both a permissive defender and a well-prepared attacker. This sometimes happens: it did in 1940, 1967, and 1991 and probably will again in some times and places. But it is not easy to create a permissive enemy by fiat. And to exploit a permissive enemy properly requires expensive training, equipment, and officer preparation. The payoff can be great when these conditions combine: Germany conquered France in a month, Israel defeated Egypt in six days, and the United States reconquered Kuwait in 100 hours. But the conditions are not always right.
This pattern poses a dilemma for the United States. The U.S. military has long privileged quality over quantity. This has produced a military with the skills and equipment to exploit offensive opportunities when they present themselves, as they did in Kuwait in 1991 and may do again in the future. But if the conditions are not right and attrition warfare results, today’s U.S. military is not built to sustain the losses this could produce. The United States suffered fewer than 800 casualties in 1991 and just over 23,000 in 20 years of counterinsurgency in Afghanistan. But in less than two years of warfare in Ukraine, each side has already suffered over 170,000 casualties. The United States has produced about 10,000 Abrams tanks since 1980; in Ukraine, the two sides together have already lost over 2,900 tanks. The United States is starting to ramp up weapon (and especially ammunition) production now. But to produce expensive weapons in the numbers needed to sustain Ukraine-scale losses will be exceptionally costly. And how will the United States replace today’s long-service professional personnel in the face of Ukraine-level casualties?
If quality can ensure quick, decisive victories, the traditional U.S. approach is sound. But if the lesson of Ukraine’s 2023 offensive, in light of past experience, is that deep and well-prepared defenses remain robust, as they have been for the last century, then quality alone may not be enough to ensure the kind of short wars of quick decisive breakthroughs that U.S. defense planning has long tended to presuppose. Quality is necessary for opportunity but may be insufficient in itself for success. And if so, the United States may need to rethink its balance of quality and quantity in a world where permissive conditions happen sometimes but cannot be guaranteed.