Airpower and Interdiction: Overcoming Defender Advantages

September 27, 2022
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On Oct. 8, 1973, the Israel Defense Forces launched a major counterattack on Egyptian positions in the Sinai spearheaded by three armored brigades. Israeli commanders expected to repeat their rapid 1967 victory over the Egyptians, but they were disappointed. Egyptian forces employed new tactics and weapons, especially the Soviet-made AT-3 Sagger anti-tank missile, to repel the Israeli attack with heavy losses. The struggles of Israeli armored forces against anti-tank missiles during the Yom Kippur War led many observers to conclude that the balance in war had shifted once again in favor of the defender. Rather than accept stalemate, however, the U.S. military incorporated lessons from the Yom Kippur War to reemphasize close cooperation between surface and aerial forces to overcome the defender’s advantage. The result was astounding, as the American military crushed the Iraqi military in the 1991 Gulf War, expelling Iraqi forces from Kuwait.

Debates about the future of war are as old as war itself. Yet, they persist, and too often pundits and analysts are too eager to declare a weapon system obsolete, only for the defender to devise ways to overcome weapons that had once been revolutionary and cutting edge. The debate surrounding the invasion of Ukraine is no different and has drawn renewed attention to the future of war. 

Much analysis about this conflict has emphasized the supposed ascendence of defensive warfare when armed with precision-guided weapons like Javelin missiles or Bayraktar drones. Even before the conflict, T.X. Hammes predicted that new weapons would drive the ascendency of the tactical defensive in warfare. David Johnson, writing in these pages, built on Hammes’ analysis, arguing that Russia’s failure to overrun Kyiv heralds the arrival of defense-dominant military operations at the operational level. Respected commentators like Phillips O’Brien now claim that new precision weapons have rendered most previous offensive military capabilities obsolete. According to these analysts, we are seeing a seismic shift in the character of war towards a stronger defensive capability.

 

 

These claims that new technologies have radically altered the balance of offense and defense in warfare are misleading. Defensive warfare has enjoyed long-standing advantages well before the advent of precision weapons. Defenders enjoy a second-move advantage since they can wait to see the attacker’s dispositions before committing their own reserves to the counterattack. This structural information advantage means that, other things being equal, defenders are better able to exploit operational mobility to concentrate forces at the decisive point. Emerging technologies may augment these larger defensive advantages on the margins, but they have not radically upset the overall balance. 

The recent claims of a new revolution in defensive strength are especially misleading because they blind us to the long history of attackers overcoming these advantages through joint operations especially the effective employment of airpower for interdiction in support of surface forces. Whether on offense or defense, interdiction of the adversary’s ability to maneuver operationally is critical to battlefield success. That Russia was not able to execute an effective aerial interdiction campaign does not invalidate the future utility of airpower in supporting ground offensives. Indeed, Ukraine’s recent successes in retaking terrain from Russia on the battlefield point to the fact that having the capability to strike far behind an adversaries defensive lines and interdicting adversary forces can still allow effective offensive maneuvers, even and perhaps especially in a world of precision-guided weapons. 

The war in Ukraine should therefore reaffirm faith in the importance of joint air-ground interdiction and drive the United States all the harder to pursue it. Building future security policy around the assumption of defensive advantage in future conflicts is a recipe for defeat against an adversary capable of effective long-range interdiction to prevent the defender from concentrating for a counterattack. The defense is the stronger form of war, but effective joint operations can still provide the attacker or the defender with the local edge. Future success on either offense or defense will thus depend on preserving operational mobility, while denying that mobility to our adversary.

The Superiority of the Defense

The difficulties of attacking an adversary in wartime are not new, and have received significant attention from military thinkers since ancient times. Attacking an adversary has also gotten harder as the operational mobility of forces has improved. When one side is much more mobile than the other, it will enjoy a major advantage, but as the general mobility of all sides improves, the advantage accrues to the defender. Prussian military theorist Carl von Clausewitz was one of the first to recognize the critical link between mobility and defensive advantage. While many of his contemporaries sought to explain the early military successes of Napoleon Bonaparte, Clausewitz himself was interested in why conquests in the later Napoleonic campaigns had become so hard. He wrote:

There is only one point that, at first sight, seems self-contradictory, and that, because it is one of the most important points in defense, is all the more in need of further development: it is how to hit the enemy’s exact center of gravity. If the defender finds out early enough by what roads the enemy will advance, and on which of them the core of his force is to be found, he will be able to confront him there… While defense may anticipate attack by general precautions… the defender also possesses the inherent advantage over the offensive of being able to make the riposte. An advance into enemy territory by sizeable forces calls for considerable preparations such as building up food stocks and supplies or equipment and so forth. This will take long enough to give the defender time to make his own preparations.

Clausewitz famously concluded that the defense was the stronger form of war because the defender’s strength lies primarily in an information advantage over the attacker. Attacking requires massing forces proactively and committing them against an objective along certain lines of attack. By comparison, a defender can wait to discover the general disposition of attacking forces and concentrate his own forces accordingly. Neither side ever has perfect information, but on balance the defender’s information about the attacker’s dispositions will be better due to his second-mover advantage. This information advantage became more important as operational mobility improved. When mobility was low, a surprise attack might seize an objective before the defender could recover and commit his own forces in riposte. As mobility grew, however, even an initial surprise would avail the attacker little if the defender sped reserves to contain the attack. 

When both sides are highly mobile, therefore, the defender benefits disproportionately from knowing how to exploit that mobility. Of course, outcomes in war are always driven by many factors, including the size and morale of the forces involved and the skill of the commanders in selecting lines of operation or deceiving the adversary. Especially effective combat forces or especially skilled leadership could and have in certain cases overcome the defender’s advantages in information and mobility. The effectiveness of Ukrainian forces and leadership no doubt accounts for part of their recent offensive success against Russian forces near Kharkiv. 

In practice, however, the information advantages of mobile defensive forces have been great. Changes in transportation and logistics accelerated in Europe throughout the 19th century with the development of better road and rail systems, while electronic communications diminished opportunities for surprise. As an early adopter of these technologies for military purposes, Prussia gained some offensive advantages in the 1860s and 1870s, leading many observers to conclude that highly mobile forces made attacking easier. Contrary examples of extensive battlefield attrition and stalemate from the American Civil War, the Russo-Turkish War, Russo-Japanese War, and the Balkan Wars were largely ignored. As other European powers matched Prussia’s operational mobility another major stalemate loomed. 

World War I served to confirm Clausewitz’s observation that high operational mobility generally favors the defensive. Like the current war in Ukraine, the violence of World War I drew attention to new weapons like machine guns and rapid-fire artillery. Yet perhaps of greater importance was the ability the defender to speed reserves by rail to halt any offensive action, denying the adversary the ability to generate enough local superiority to exploit an attack. Even successful initial offensives were often quickly smothered by a tide of reserves sped to the battlefield by trains. The result was stalemate.

Overcoming the advantages of the defense is thus an enduring problem. Yet, the defender’s ability to react provides a durable information advantage over the attacker, who must commit his forces first. Increases in operational mobility have only increased the defender’s advantage, allowing the defender to respond rapidly even when the attacker achieves initial surprise. In recent years, information technology is further increasing the defender’s advantages by making it even harder for the attacker to mass forces decisively without providing the defender with an easy target for counterattack. Even though Russia surprised Ukraine in its initial offensive, Ukrainian forces were able to quickly mass to parry Russia’s thrust at Kyiv. Faced with such a challenge, it is only natural that Hammes, Johnson, and O’Brien conclude that future wars will see the general superiority of the defensive.

Airpower and the Offensive

Following World War I, militaries around the world searched for ways to restore offensive mobility to the battlefield. One of the most important thinkers in the English-speaking world was J.C. Slessor, a Royal Air Force officer who had served in World War I. Echoing Clausewitz, Slessor observed that the general superiority of the defensive exhibited in that war was likely to endure, driven by the continued ability of the defender to speed reserves to the point of attack. 

While ground forces would struggle alone on the offensive, Slessor saw significant opportunity for joint air-ground action to restore offensive movement. While many early theorists of airpower focused on the “strategic” ability of aircraft to destroy enemy cities and compel capitulation absent confrontation on the battlefield, Slessor closely considered the ways in which aerial forces might support ground forces by attacking enemy reserves and mobility directly. Seizing air superiority and interdicting enemy movement could help an attacker break through enemy lines because a defender could not respond adequately if his road and rail system were interrupted by continuous aerial attack. Similarly, a defender who enjoyed air superiority would be able to strangle any offensive action by denying it the supplies necessary to sustain its forward motion. Slessor predicted that joint employment of air and ground forces would prove more important in future campaigns than the defender’s historical advantages. The side that could better disrupt its adversary’s mobility through aerial interdiction, whether on offense or on defense, could concentrate sufficient forces to prevail at the decisive point.

Slessor’s vision of joint air-ground operations restoring offensive mobility was borne out by the experience of World War II. Support from the Luftwaffe played an important role in Germany’s early victories in Poland, Norway, and France. Following the German invasion of the Soviet Union, the shifting balance of power on the eastern front also tracked the relative balance in the air. The initial German offensive made rapid gains in 1941 when the Luftwaffe enjoyed predominance. These gains quickly gave way to grinding conventional battles as the Red Army began to contest German command of the air. By 1944, the collapse of German airpower saw the Red Army seize the offensive. The Luftwaffe’s decline was no coincidence, but rather a product of Western allied strategy aimed at destroying German airpower through bomber offensives. Aerial superiority provided the basis for the Allied invasion of France and the subsequent destruction of German forces both east and west.

Airpower’s ability to support rapid offensive action has continued since the Second World War. American airpower was critical to holding back and reversing North Korean gains in the summer and fall of 1950. Israel’s air superiority was critical to its rapid successes in the 1967 Six Day War. Israeli forces struggled early in the 1973 Yom Kippur War, but as the aerial balance shifted in favor of Israel so too did the Israeli army reassume the offensive. The Iraqi military waged an eight-year war of attrition against Iran, in which neither side seized control of the air. That same Iraqi military was utterly destroyed in a matter of weeks in Desert Storm, in which American-led aerial attacks played a critical role in hollowing out Iraqi resistance. American-led air campaigns have repeatedly enabled ground forces to seize terrain from determined adversaries in Afghanistan, Iraq, Libya, and Syria. 

While warfare has changed considerably since Slessor’s day, no new technology has invalidated his basic insight about the role of airpower in supporting ground maneuver through interdiction. While air defenses have improved, so have techniques for defeating them. Air superiority thus continues to be a valuable asset for joint forces. Similarly, the development of precision-guided weapons and networked sensors has only enhanced the capability for deep attacks on enemy logistics and reserves, capabilities that can be exploited by either the attacker or the defender. 

Despite the longstanding strength of the defense on the ground, attackers have been able to seize the offensive by exploiting joint air-ground operations to disrupt the defender’s reserves. The converse has also been true, in that attackers subject to aerial interdiction have struggled to maintain offensive momentum, as demonstrated by the suffering of German, Chinese, and Vietnamese forces in the face of American airpower in Operations Overlord, Strangle, and Commando Hunt. The defender’s general advantage in information and mobility is thus heavily modified by the ability to seize and exploit air superiority in support of ground operations. Only when neither side can effectively interdict the other’s operational mobility does the general superiority of the defensive reassert itself. Keeping this joint imperative in mind better allows us to understand what is happening in Ukraine today.

Observations from Ukraine

While coverage has focused on Ukrainian weapons, little attention has been paid to the operational level of Ukraine’s defense. While it is always difficult to map an ongoing conflict, a tentative review suggests that Ukrainian forces have moved quite a bit. They were poorly positioned to meet initial Russian offensives, which achieved some measure of surprise. The first few days of the war saw extensive redeployment of Ukrainian forces to meet the Russian lines of advance. Concentration of Ukrainian forces rose especially around Kyiv by late March. As the Russians redeployed towards the East and South, Ukrainian forces also reconcentrated to meet those new lines of advance. Most recently, Ukrainian forces concentrated against lightly defended areas near Kharkiv prior to their offensive. In broad contours, then, we can see that Ukrainian forces have adopted the long-standing advantages of the defender to maneuver reactively, concentrate quickly against the attacker, and exploit the advantage Kyiv has in areas behind the front lines.

We also know that Russia failed to achieve air superiority sufficient to defeat Ukraine’s operational mobility. While the Russian military has underperformed across the board, the Russian air force has been particularly dismal. Ukrainian forces have leveraged their air and anti-air assets to deny Russia easy access to Ukrainian airspace, but much of the problem seems to be that the Russian military never planned to seize air superiority or conduct deep interdiction of Ukrainian forces. As a result, Ukraine now enjoys an advantage in mobility because Russia has struggled to strike its supply lines. The initial wave of Russian air and missile attacks was not followed up with an effective campaign to destroy Ukrainian air forces, suppress Ukrainian air defenses, and interdict the movement of Ukrainian ground forces away from the front. The specific weapons employed may be new, but the indecisive operational result was not all that different from the First World War or the Iran-Iraq War.

While Ukraine has not been able to achieve classical air superiority over Russian forces, their current counteroffensive further demonstrates the importance of joint interdiction in enabling successful offensives. Longer-range rockets like the American-made HIMARS coupled with short- and medium-range unmanned aircraft have allowed the Ukrainian to strike Russian forces in greater depth, disrupting their ability to supply their forces and maneuver reserves into position for counterattacks. Many of the very same weapons that were so effective in interdicting Russian forces moving offensively towards Kyiv were then applied to interdicting Russian forces moving defensively towards Kharkiv. How far Ukrainian forces will advance remains uncertain. What is certain is that of the many things we can learn from the war in Ukraine, the idea of a new superiority of the defense is not one of them.

Implications for the Future

The defense does enjoy substantial advantages, but these are rooted in the superior ability to gather information on the disposition of the attacker’s forces and exploit that information through operational mobility. Too often, analysts imagine the defender as immobile, awaiting the arrival of the attacker. However, in practice effective defense relies heavily on mobile reserves to parry the attack. In doing so, the defender’s second-mover advantage means that he can observe the attacker’s commitment of forces prior to making his own. Of course, the defender may not always realize this advantage, but the long record of grinding attritional campaigns over the last century suggests that in practice defenders often do meet the attacker effectively and stymie the advance. Given the size and mobility of the forces involved, Russia’s initial invasion of Ukraine might very well have failed even if the forces involved were armed with the weapons of 50 or 100 years ago. Ukraine’s ability to maneuver and mass reserves mattered more in defeating Russian offensives. 

The defender’s advantages are therefore real, but they are relative and contingent on mobility, which is highly sensitive to disruption by enemy action. Precision conventional weapons increasingly allow combatants to attack and disrupt the other’s operational mobility, but these weapons are applicable to attackers or defenders alike, not a special province of the defender. In a future war, the defender’s ability to resist will depend heavily on his ability to degrade the attacker’s operational mobility while retaining his own. Should the attacker gain the advantage in this deep fight, especially through the air, superior weapons will not help the defender reach the battlefield in time. Ukraine’s own recent offensive successes point in this direction. 

Understanding the scope conditions of Ukraine’s battlefield success has important implications for future planning and force development of other small powers. A country like Taiwan worried about waging a cost-effective defensive could still purchase masses of shorter-range rockets and artillery to defend themselves. Such weapons can prove effective under the right circumstances, as Ukrainian forces have shown. Yet large numbers of short-range precision weapons will not be enough to defeat an adversary who could use long range air and ground fires to sustain its own mobility while disrupting that of the defender. Effective defense will require a mix of forces able to attack the adversary in depth while also preserving one’s own mobility.

Recognizing the defense’s contingent advantages can also help us better appreciate the sorts of capabilities that the United States should prize in its own joint force going forward. Success in future conflict, whether offensive or defensive, will depend significantly on the ability to disrupt the adversary’s operational mobility in the deep fight. Rather than resigning ourselves to a future of military stalemates, we should continue to emphasize air and surface forces working closely together to overcome adversaries in future wars. This also means preparing to exploit air superiority correctly. Especially in a world of nuclear-armed states, future wars will likely see air forces supporting local actions rather than risking nuclear escalation by launching independent “strategic” attacks. The real objective will be to ensure local air superiority in support of surface forces by interdicting enemy mobility and supply. Russia’s invasion of Ukraine has demonstrated the risks of failing in the joint fight, but not the impossibility of success.

 

 

John D. Maurer is a professor of strategy and security studies at the School of Advanced Air and Space Studies (SAASS), Air University, and a non-resident fellow at the American Enterprise Institute (AEI). His book on American nuclear strategy and arms control policy, Competitive Arms Control, was recently published with Yale University Press. The views expressed are his and do not reflect the official policy or position of the Air Force, Department of Defense, or the U.S. government.

 

Image: U.S. Air Force photo by Staff Sgt. Andrew Lee.