Bending the Principle of Mass: Why That Approach No Longer Works for Airpower

September 15, 2020

It is one of warfare’s oldest questions: What is mass, and what advantages accrue from sheer numbers? The concept has variously been defined as being about “the superiority of numbers,” or “concentrating the effects of combat power.”

While commanders often desire numerical superiority over their adversaries, they are not always able to achieve it. Instead, commanders use methods such as maneuver to achieve a local superiority in combat power. Maneuver is just one of many ways commanders attempt to artificially inflate the mass of their forces. Others include improving command and control, enhancing lethality, and seeking to possess better information than their opponents. All of these methods can allow assets to contribute relatively more to a fight, thereby potentially offsetting a requirement for mass. Over the past 50 years, the United States has progressively placed more emphasis on artificial mass — command and control, lethality, and superior information — as a substitute for actual mass.



A critical question, however, is what happens when an adversary combines these measures with actual mass? If both sides are lethal, networked, and effectively commanded, then what factors determine who has the advantage? As Lawrence Freedman argues, the “sensible application of superior resources tends to be successful.”

As a result, this question is becoming increasingly relevant for the Department of Defense as a whole. After decades of either a qualitative and/or quantitative advantage against likely opponents, it is now facing a massive buildup of increasingly modern Chinese forces. Just weeks ago, China announced that its fifth-generation fighter, the J-20 Mighty Dragon, would be entering mass production. How will the United States fare if faced with modernized mass?

The Department of Defense, and more specifically the U.S. Air Force, should evaluate its definition of mass in the context of future air warfare. While relying on numbers alone is too simplistic, Air Force leaders should recognize the importance of having sufficient numbers to fight, take losses, and continue to provide relevant capabilities to combatant commanders. The geography and threats in the Indo-Pacific necessitate hard thinking about requirements such as range, basing considerations, and survivability. Thus, for example, it is not enough to merely have numbers of short-range systems if the region demands longer range. Similarly, it is not enough to build attritable systems hoping the adversary will expend resources combating them. Adversaries will attempt to target all elements of American airpower. The Air Force should lead the Department of Defense in thinking through the implications of peer conflict — namely, that artificial advantages in mass may no longer be sufficient and that real numbers might be required to sustain a war effort within an anti-access/area denial bubble.

Trends in Mass

The shift away from traditional notions of mass arose in part after the Vietnam War, when the nation began considering how to defend Europe from the Soviet Union using conventional weapons. Precision weapons, high-performance aircraft, and robust command and control all helped to offset a Soviet advantage in sheer numbers. This marked a departure from thinking during World War II and the early Cold War years, when the United States pursued varying blends of both qualitative and quantitative edges over its opponents.

Now, however, the United States steers away from ideas about traditional mass as decidedly old-fashioned. By contrast, it stresses the promises of artificial mass (lethal systems, data, networks, etc.) at the expense of adequate numbers of aircraft and weapons. While these measures to improve force effectiveness are beneficial, are they sufficient? The Department of Defense should critically examine the importance of traditional notions of mass (i.e., numbers) in the context of a future fight.

Air Force thinking may be hamstrung by its current definition of mass, in which mass is not “based solely on the quantity of forces and materiel committed.” Rather, “[a]irpower achieves mass through effectiveness of attack, not just overwhelming numbers.” Under this definition, traditional mass would appear to not be necessary as long as forces are able to attack effectively. Air Force doctrine is not alone in this assertion. Airpower scholar Philip Meilinger similarly explains that “speed and surprise can sometimes substitute for mass” — although the promise of only being able to make up for mass “sometimes” offers little reassurance. What happens if forces are less effective than hoped for or if forces fail to achieve surprise?

Some Air Force officers are well aware of this problem. As Gen. Jeff Harrigian wrote recently, “we must not forget that mass is an important principle of war.” Harrigian refers to a more traditional understanding of mass as sheer numbers, a conception that the Department of Defense has tried to sidestep as well. Joint Publication 3-0 Joint Operations defines mass as resulting not from “concentrating forces” themselves but the “[m]assing effects of combat power” that “can enable even numerically inferior forces to produce decisive results and minimize human losses and waste of resources.” It also provides historical examples, explaining how in Operation Just Cause in Panama it “relied more on situational awareness, mobility advantages, and freedom of action than on mass.” Yet for Operation Desert Storm, it describes the importance of a “massive and continuous air operation.” It uses that same language for Operation Enduring Freedom, stressing the importance of “massive and effective close air support.” If Enduring Freedom, which required little to achieve air superiority, necessitated such mass, it is difficult to conceive of what a peer conflict might require. If the B-1 bomber fleet was heavily taxed flying in a relatively permissive environment in the Middle East, what would happen if it also suffered combat losses in a conflict with China or Russia?

Sun Tzu, the master of maneuver, refused to reduce war to the simplistic notion of war being merely a “matter of the more troops the better.” Still, he offered no easy solutions for the problem of mass. One should go on the offense with “abundant” capabilities, even as he advised “adopt[ing] a defensive posture when our resources are insufficient.” Without mass, armies had the best chance at victory depending on how one “modified by dividing and joining” their troops. In such situations, an army succeeded when it kept itself “intact” as part of a “single whole” while forcing the enemy’s army to fracture “into ten parts.”

This way of maneuver to achieve mass reflects the organizational advantage of centralizing airpower. While massed airpower has provided a useful, if indecisive, capability in the asymmetric conflicts of the past two decades, it has increased importance in direct peer competition.

It is unclear if any strategies currently being explored will reduce the requirement for mass. For example, one Air Force officer argued for taking a more indirect approach to a possible conflict with China by focusing on a long-range strategic interdiction campaign. Although such a strategy might be both prudent and effective, it is unclear how it would reduce the numbers required to deter aggression or execute war plans. For example, the author still advocates “attrit[ing] PLAAF [People’s Liberation Army Air Force] and PLAN [People’s Liberation Army Navy] air forces, particularly bombers, naval forces, and naval auxiliaries, to the point where they can neither project military power nor defend against U.S. power projection.” It is unlikely U.S. combat forces would be so effective as to preclude losses or the need for numbers in such an endeavor.

Mass and Airpower

Historically, airmen have had a mixed relationship with the idea of mass. In early Air Corps doctrine, numbers were essential. One of the earliest ideas of the world’s fledgling air services was to overwhelm enemies with massive numbers of bombers, a strategy that inherently required large numbers of aircraft. The desire for mass largely continued through World War II and into the Cold War. However, after the Vietnam War, Air Force mass started a long downward trend. The post-Vietnam drop in aircraft numbers was largely caused by the retirement of many platforms, as the mass built in during the 1950s came to the end of its service life. Another large drop in numbers came with the post-Cold War peace dividend. Today, numbers are further declining as the Air Force retires legacy systems without funding for numerical replacements.

Figure 1: U.S. Air Force Aircraft Numbers, 1950 to 2016

Source: The Mitchell Institute for Aerospace Studies

In the past, some have rationalized this reduction in numbers by pushing back at the idea of being bound by the principle of mass in the first place. Namely, airmen cite three different concepts as reasons numbers can decline without losing effectiveness: command and control, advancements in aircraft and weapons, and information.

In even the earliest days of Air Force history, the topic of command and control was paramount. For example, one of the fathers of the U.S. Air Force, Billy Mitchell, learned how to organize airplanes by “concentrat[ing] the bulk of bombardment and pursuit so that he could ‘hurl a mass of aviation at any one locality needing attack.’” One airpower scholar suggests that this development had a critical importance in U.S. aviation history by “establish[ing] the principle of concentration as aerial dogma.” While perhaps overstated, this idea manifests itself today with the Air Force placing great importance on centralized command of airpower at the theater level to create mass as needed.

Advancements in technology, such as stealth aircraft and precision weapons, provided another rationale for reducing numbers. If it took 4,500 bombers and 9,000 tons of bombs to destroy a small house in World War II, it only took 95 aircraft and 190 tons of bombs in Vietnam. And in Desert Storm those figures shrank to far less, with a concomitant loss in casualties, to .05 percent. In the first day of the Gulf War, the coalition planned to strike more targets in one day than the Eighth Air Force had struck in 1942 and 1943.

The importance of this redefinition is that, by these calculations on their own, mass is no longer as important. There would be no need for a repeat of the early Cold War if the Air Force pursued huge numbers of bombers to launch a nuclear attack against the Soviet Union. Instead, small numbers of survivable bombers could deliver large numbers of weapons with precision.

Some analysts now argue that data will allow the Air Force to get away without having mass. In a four-part series in War on the Rocks about achieving air superiority in 2030, one Air Force general did not mention mass until the third article, and then only briefly. He discussed mass in the context of data-to-decision thinking for achieving air superiority. Data-to-decision thinking seeks to enable decisive decision-making by leveraging data gathered across the joint force. As he explained:

[Data-to-decision] is the connective tissue that ties our stand-off and stand-in forces together. This linkage is what allows for the precise application of kinetic or non-kinetic fires against the adversary system in mass. … Eventually, as tempo increases, the mass of effects brought to bear culminates the enemy force and defeats its A2/AD [anti-access/area denial] strategy. The adversary system is rendered ineffective, allowing the full range of joint operations.

Or, in other words, the Air Force will make its forces more effective by leveraging information. By doing so, the Air Force will ensure its mass is applied in the highest-impact way at any point in time and space.

These three rationales for mass reduction — command and control, technology, and information — do much to improve the lethality and effectiveness of the Air Force. However, they suffer from a number of flaws that could prove fatal to the Air Force’s ability to compete against a peer competitor.

Problems with Current Thinking About Mass

War is a competitive endeavor. While the United States has made incredible progress in aircraft and weapon lethality, its adversaries have not been idle. American airpower has largely been allowed to develop and operate in a position of extreme overmatch since the end of World War II. Today’s thinking about mass seems to ignore, or merely pay lip service to, the idea of enemy interaction and the fog of war. Analyzed in the context of a competition against a well-resourced and resourceful adversary, however, two pillars of mass reduction begin to crumble: technology and data.

Technological advancements in aircraft and weapons performance have enabled the Air Force to achieve effects that World War II airmen could only dream of. Today’s aircraft are capable of attacking multiple targets with precision over enormous ranges. But the conflicts used to tout the advantages of today’s aircraft and weapon systems have all featured relatively permissive operating environments. While coalition accomplishments over Iraq in Operation Desert Storm were impressive, the coalition possessed a better-trained, better-equipped, and larger air force than Iraq. Similarly, air operations over Iraq and Afghanistan for the past two decades have faced limited aerial opposition.

How would the Air Force fare if it had to compete against an adversary with similar technology, training, and numbers? Militaries have always tried to have a technological edge over their adversaries. Unfortunately, when equivalent technology collides, attrition results. Air forces in World War II invested huge amounts of resources into improved aircraft performance, training, and tactics. As Williamson Murray wrote, “[t]he air struggle … rested on numbers of aircraft, industrial capacity and production, and availability of trained aircrews.” It was these factors, more than any advances in aircraft speed or bombing accuracy, that led to the Luftwaffe’s defeat in World War II. The Luftwaffe could not create a technical edge large enough to offset a deficiency in mass. The cost to sustain the Army Air Force’s mass was significant, however. The Eighth Air Force alone suffered more personnel killed in action (roughly 26,000) than the entire U.S. Marine Corps (24,511).

Information is similarly problematic. Although information can and does enable increased force effectiveness, its decisiveness is subject to debate. Coalition efforts in the “Global War on Terror” have been drowning in information for years. And while the coalition has made plenty of decisions based on data, those have often been disconnected from the larger strategic picture. Similarly, David Kilcullen argues that adversaries can hide within and exploit data. No competent adversary will be so awed by Air Force information networks that they will surrender. Adversaries will adapt to and attempt to exploit any actions by the Air Force. For every action, there is an equal and opposite reaction.


U.S. Air Force efforts to bend the principle of mass have resulted in a highly capable and lethal force. This force is also inadequate for extended competition against an adversary with mass of its own. While the Air Force has been making some efforts to achieve mass such as the mass production of the F-35, procurement of the F-15EX, and development of low-cost attritable aircraft technology, these sidestep the problem. Adversaries will not only choose to fight the Air Force’s attritable technology. Instead, they will target all elements of Air Force power projection: bombers; intelligence, surveillance, and reconnaissance aircraft; tankers; fighters; and attritable aircraft. Mass is important across the force.

The Air Force, given its recent wrestling with more traditional notions of mass, should lead efforts in the Department of Defense to ensure it is prepared for a conflict against a peer competitor. The first action is to broadly review how it defines mass in doctrine. Can the principle of mass actually be bent through increased effectiveness? Or does that situation apply only in permissive environments or against overmatched adversaries? Is the definition adequate for peer competition?

Second, the service should study its ability to operate forces given historical peer-conflict attrition levels. In World War II, the Air Corps not uncommonly lost 5 percent of dispatched aircraft on strike missions. That loss rate was echoed by the Israeli Air Force in the Yom Kippur War. Can the U.S. Air Force sustain a loss rate of 5 percent over likely conflict time horizons? Are there assets whose loss would have a more debilitating effect on the force than others? Do plans incorporate this possibility?

Finally, the Department of Defense more broadly should pay special attention to the efforts of potential adversaries, such as China, to increase their own mass. China is currently the world’s second-largest air force, with more than 600 fourth-generation fighters and an increasing number of fifth-generation fighters. By contrast, the U.S. Air Force has more than 2,000 fighters, of which more than 350 are fifth-generation. However, as demonstrated by the tremendous growth of the People’s Liberation Army-Navy over the past 20 years, this advantage could nullified in the coming decade.

The recent announcement that the J-20 would be entering mass production should serve as a warning sign that other nations are taking the idea of mass seriously. While it is possible that advantages in technology and networks could compensate for some deficit in mass, it would be fatal to rely on those advantages only to find out they were negated. The Air Force should ensure it has the numbers, or industrial capacity to create the numbers, necessary to prevail even without a significant technological advantage.


When the United States entered World War II, the Air Corps thought unescorted daylight precision bombing could win the war. It was wrong — at great cost in blood and treasure. But mass allowed leaders to quickly replace losses and simultaneously grow the force. In other words, mass allowed leaders to make mistakes in the uncertainty of a new conflict. Peacetime planners before World War II were wrong about the tactics of that war, but they set commanders up for success by providing mass that could be adapted to the needs of wartime. And even if overt conflict is unlikely, mass will remain essential for deterrence.

Today’s peacetime planners don’t have to get everything right, but they should ensure commanders have the resources they need to fight and win. This means critically examining definitions of mass, reevaluating the likelihood of losses, and once again paying attention to one of warfare’s oldest considerations: numbers.



2nd Lt. David Alman is an Air National Guard officer attending specialized undergraduate pilot training. He holds a B.S. and M.S. in aerospace engineering from the Georgia Institute of Technology and works as a management consultant in his civilian career.

Dr. Heather Venable is an associate professor of military and security studies at the U.S. Air Command and Staff College and teaches in the Department of Airpower. She is the author of How the Few Became the Proud: Crafting the Marine Corps Mystique, 1874–1918. She also edits for The Strategy Bridge and The Field Grade Leader and is a non-resident fellow at Marine Corps University’s Brute Krulak Center for Innovation and Creativity. These opinions are the authors’ own and do not represent that of the U.S. Air Force or the Department of Defense.

Image: U.S. Air Force (Photo by R. Nial Bradshaw)