September 29, 2023
Heather Venable is back with another Dusty Shelves entry that looks at William C. Sherman's "Air Warfare." When most airpower advocates championed theories of strategic bombardment in the inter-war years, Sherman presented a much more nuanced framework that examined the tactical and operational applications of the new domain. It's a great read that's still a valuable lesson today because the author offers no easy answers amongst a field of theorists that offered the resounding answer: strategic bombardment!

During the inter-war air period, British and American airmen largely pursued theories of strategic bombardment.

It is one of the great conundrums of airpower history: how did airmen seemingly learn the exact opposite lessons from World War I that one might assume they should learn? After all, airpower seemingly had proven itself to be invaluable in supporting the Army in many ways, from providing observation to artillery spotting. Rather than learn a clear-cut lesson though, interwar airmen zeroed in on strategic bombardment, or the use of airpower to bypass fielded forces to strike directly at the source of an opponent’s strength, such as major cities or factories. This particular lesson in large part was an Anglo-American Atlantic phenomenon, to some extent bypassing French, Italian, and even German airmen.

 One American airmen does not fit neatly into either of those two categories, neither fully buying into strategic bombardment nor seeking to have airpower remain largely as a supporting capability to the Army: U.S. Army Air Service officer William Sherman. Reading his 1926 work entitled Air Warfare leads to a more nuanced framework for thinking about the range of kinetic airpower employment while avoiding the tendency to label individuals either as either “tactical” or “strategic” advocates. Additionally, the very fact that Sherman spent some of his interwar years teaching at Army schools and developing tactics may have inoculated him against some of the more zealous tendencies of some of his counterparts. As a result, he took a more tactical and operational approach that made his work distinctive.

Context of Strategic Bombardment in Interwar Period

During the interwar air period, British and American airmen largely pursued theories of strategic bombardment. Prominent Italian theorist Giulio Douhet most famously epitomizes this approach. His writing established the framework for much future thought, although his thoughts on air superiority are often dimmed out by his vision of making war so terrible—by gassing civilians in cities—that politicians would quickly surrender. Some airpower scholars, though, have examined more how he planned to operationalize these ideas, with one summing Douhet’s thinking as consisting of three steps: 1) first acquire command of the air 2) “neutraliz[e] an enemy’s strategic ‘vital centers’” and 3) defend resources on the ground while “taking to the offense in the air.” Arguably, little significant difference exists between steps two and three, although land warfare proponents might note how Douhet sought to limit their efforts solely to the defense.

In practice, Douhet’s approach led to an excessive emphasis on the second stage of this process: the attack of cities. Increasingly in the interwar period, both British and American airmen stressed “high-altitude bombing” as the ideal way to employ airpower, a radical departure from its initial employment as reconnaissance and artillery spotting. 

The seed of these ideas had disseminated across the Atlantic as early as 1917, when American airman Major Edgar Gorrell visited Italy and learned about this incipient strategic bombardment theory. His trip report concluded that the Allies should pursue this course of action to end the war, using airpower to target factories producing materiel. This economic approach to warfare did not differ greatly from the traditional British approach. And, while the report did make some mention of attacking civilian morale, it appeared mostly as a secondary effect.

Over the course of the interwar period, the two nations pursued some differences in operational employment. Lord Hugh Trenchard carefully shepherded the newly-independent Royal Air Force after its birth in 1918, and his influence resulted in a greater focus on attacking enemy non-combatant morale. This approach paralleled the stress he placed on undermining the morale of enemy combatants while simultaneously seeking to boost that of his own pilots. In short, he took the idea of airpower as inherently offensive and pursued it to the maximum, advocating a problematic “relentless and incessant offensive.”

Themes of Air Warfare

Major William Sherman published Air Warfare in 1926,drawing upon his time instructing air tactics at the Army’s Command and General Staff College. The handful of airpower scholars to analyze Sherman have considered him to be a Billy Mitchell protégé. Such an interpretation, though, requires a very selective reading of his work. Exemplifying this cherry-picked analysis, one scholar explains: 

According to air theorist William Sherman, the relative importance of the infantry in war was not permanent; the airplane (if used properly) could diminish the queen of the  battlefield’s stature, especially by acting decisively against ground forces.

Such an indictment, were it correct, would place Sherman clearly in the camp of airpower zealots like Giulio Douhet, whose theory rested on the central assumption that the advent of the airplane made traditional warfare largely irrelevant. As will be shown, however, Sherman’s overarching vision for airpower balanced both traditional and new ideas for employing military force. He even suggested, for example, that cavalry could find new roles on the modern battlefield if airpower supported it. As Lori Henning has argued compellingly, cavalry was not completely obsolete after World War I, as many have assumed. Here, then, Sherman tried to think of creative ways to support the land campaign, exactly the opposite of what one would expect based on existing historiography.

Sherman: How much strategic bombardment?

Sherman’s Air Warfare consists of ten chapters, the first introducing the general principles of air warfare, narrowing in on those he found particularly relevant to airpower: 1) mass 2) economy of force 3) the offensive 4) security 5) simplicity. In essence, Sherman reduced these to the notion of centralizing offensive airpower to use it decisively against a key point, taking a largely Clausewitzian approach, drawing upon traditional land theory rather than rejecting it as irrelevant. Indeed, his emphasis on principles of warfare may reflect the influence of his time as a student and instructor at the Army’s Command and General Staff College, given how actively that school adopted and taught them after World War I.

Still, this approach also aligned with the general Anglo-American cross-Atlantic school of thought regarding an emphasis on offensive airpower that verged upon the dogmatic. Sherman tried to avoid this tendency by relying on sound evidence, labeling the best evidence as that which could be derived from mathematics or the continuity of human nature to support his line of reasoning. However revolutionary the airplane might be, for Sherman it would not overturn basic principles of warfare.

His use of Foch as an authoritative voice demonstrated more tactfulness than outspoken advocates like Mitchell because he used support from generals from the traditional domains rather than railing against them

Enthusiastic advocates of strategic bombardment tended to focus on airpower’s possible capabilities rather than actual ones. Unsurprisingly based on the continuities he established with traditional war theory, Sherman advanced his ideas more cautiously, balancing the possibility of vastly improved airpower capabilities—given how much it had advanced between 1914 and 1918—with context, noting that “limited cases” should not be applied “universal[ly].” In this way he sought to ground the lessons he took away from World War I in sound logic rather than enthusiasm or future promise.

As a result, Sherman kept discussions of strategic bombardment relatively tangential. In his most forceful advocation for the notion, he referred to the French general who had served as supreme commander of Allied forces during World War I, Marshal Ferdinand Foch, to validate the idea that one might be able to exert “such pressure …. on civilian populations as to end war through the action of the air force alone.” His use of Foch as an authoritative voice demonstrated more tactfulness than outspoken advocates like Mitchell, because he used support from generals from the traditional domains rather than railing against them. In this light, it is perhaps notable that Mitchell—his supposed mentor—had been court martialed at the end of 1925 for his outspokenness. It is unknown whether this cautionary example had time to influence Sherman’s book. But, given the rather short amount of time that passed before the book’s 1926 publication, it seems unlikely that Sherman would have had time to make major revisions and reign in more outspoken opinions.

The essence of his theory—not much?

In the rest of the book, Sherman shifted to the airplane itself, describing its basic characteristics as well as basic offensive and defensive aerial tactics. Four succeeding chapters addressed the roles of observation, pursuit, attack, and bombardment. Sherman then concluded with three somewhat disparate chapters on anti-aircraft defenses, logistics, and naval aviation.

As such, Sherman offered probably the most wide-ranging work of any interwar airpower practitioner, although at the cost of proffering a long-lasting theory approach given his tactical emphasis at times. Sherman, for example, provided a detailed treatment of various characteristics of military aircraft, to include discussion of airships and some naval aircraft. Including such practical factors as wing loading and weather made Sherman unique among the interwar writers, arguably providing the most applied and technical discussion of anyone. The strength of this approach was that many theorists tended to let their imaginations outrun current technical possibilities. By contrast, Sherman remained firmly grounded in the possible. On the other hand, such a tactical perspective was not conducive to sound theory, which is notable for its ability to endure the changing character of war.

Sherman also engaged in a number of seemingly tangential discussions ranging from the tactical implications of parachutes to differences in leadership requirements for enlisted airmen. While in some ways this approach absolutely reinforces the advantage of his work—that he had such a broad perspective on airpower—on the other hand it prevented him from providing a cohesive theory because he struggled to incorporate all of his strands into one tapestry. Perhaps his education and experience had yet to propel him into a more operational- or theater-level approach to considering airpower employment.

And, in regard to airpower employment, he fell into lock step organizationally, using the U.S. Air Service’s division of airpower into four roles of observation, pursuit, attack, and bombardment, devoting about thirty pages to each role. Yet he also remained balanced, devoting as much to the supporting role of observation as he did to the independent one of strategic bombardment. Indeed, his chapter on observation may be the most creative of the four, as he argued for observation’s increasing importance in a future war.

As already mentioned, cherry picking Air Warfare has led some to conclude that Sherman strongly advocated strategic bombardment and believed that airpower made traditional warfare obsolete. This conclusion stems from the teleological nature of scholarship on the interwar period. Given how U.S. and British airmen sought to win through strategic bombing in World War II leads scholars to hunt in every nook and cranny for any evidence regarding the rise of this theory while ignoring other aspects of airpower thinking. Indeed, scholars would be better served by no longer referring to the period as an interwar period, precisely because that approach leads to a fixation on finding the connective tissue between World War I and II.

Sherman thought carefully about lessons from World War I while seeking to anticipate how another major war might be different, all the while eschewing some of the trendy ideas about airpower employment, weaving together disparate threads to offer theories still well worth reading today. As Colin Gray points out, applying airpower requires paying attention to its context. In some ways, then, Sherman’s vaguer and more all-encompassing theory is valuable precisely because it offered no easy prescriptions.

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 also is the author of How the Few Became the Proud: Crafting the Marine Corps Mystique, 1874-1918.

The views expressed in this article are those of the author and do not necessarily reflect those of the U.S. Army War College, the U.S. Army, or the Department of Defense.

Photo Description: Martin MB-2 (NBS-1) cockpit in the Early Years Gallery at the National Museum of the United States Air Force. (Inset) – The Martin NBS-1 was a military aircraft of the United States Army Air Service and its successor, the Army Air Corps. An improved version of the Martin MB-1, a scout-bomber built during the final months of World War I, the NBS-1 was ordered under the designation MB-2 and is often referred to as such. The designation NBS-1, standing for “Night Bomber-Short Range”, was adopted by the Air Service after the first five of the Martin bombers were delivered.

Photo Credit: U.S. Air Force Phot

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