What is a military innovation and why it matters

ABSTRACT The study of military innovation is one of the most important topics in the strategic studies arena, but when it comes to defining the term ‘military innovation,’ there is a remarkable lack of consensus. Lack of agreement on a definition makes it harder to advance knowledge beyond specific cases and for ongoing research to have policy relevance. Currently, what one might consider an innovation another might call an adaptation of an existing technology or tactic, or neither. To move forward, we survey dozens of existing studies and review articles for proposed definitions and examples of military innovation. We locate common and differentiating themes across a wide range of definitions and (at times) conflicting conceptual terminology. We then propose a new framework for thinking about military innovation that builds on existing research and suggests a path forward for future research. Finally, in an online appendix, we demonstrate the plausibility of the framework applied to prominent cases.

through World War I trenches, a military innovation or merely a technical invention? Must an invention 'succeed' on the battlefield to be a military innovation? If so, is the full innovation the tank itself, or the tank combined with the use of radios, trucks, and airplanes? Similarly, is what makes blitzkrieg a military innovation more advanced tanks, or their use along with other technologies and new infantry maneuver tactics? How important is the adoption of not only the technical components of an innovation, but also the organizational system? 1 The existing military innovation literature fails to provide clear and consistent answers to these questions. Theories of when military innovations occur and how they spread have been grouped and regrouped across their proposed (and often disputed) drivers, yet less attention is paid to what such theories are seeking to explain, and whether they are indeed comparable. 2 Clearer foundations would make it easier to aggregate knowledge and study how and when militaries change their behavior, and what that means for international security. The roots of military innovation studies and its conceptual terminology also require deeper comparative analysis. 3 This article does not seek to organize the existing literature across explanations of military innovation. Rather, it confronts the theoretical differences between what such explanatory models are trying to explain and argues for a new path forward. We survey the proposed definitions and cases considered in almost 100 scholarly texts that examine military innovations. Even within such a limited sample, we find a substantial variation across definitions. While scholars largely agree that military innovation involves the occurrence of an organizational change (how big or small varies), there are divergences: the role of technology as opposed to (or in conjunction with) tactics, the political purpose an innovation serves, the existence of an innovation process, the direction of innovation (bottom-up, top-down, or horizontal), and the role of success remain disputed.
Many of these cleavages occur because innovation is both an outcome and a process, and existing definitions often represent different stages. These definitions are thus best considered as components of a larger framework containing a series of steps. The first stage of this process is invention, when new technologies or tactics are created, or existing technologies or tactics are applied to specific operational problems in new ways. This is followed by the incubation stage when the invention gains status and influence through both top-down and bottom-up processes. The third stage is implementation where political will leads the community of interest to adopt the innovation. It is at this point that a state becomes capable of fully operationalizing the innovation. We further argue that a military innovation need not be successful to be considered an innovation, nor must it involve technological or doctrinal changes. Finally, in an appendix, we apply our proposed framework to two illustrative cases where there is general agreement that they constitute military innovations, but less so regarding the process -population-centric counterinsurgency (COIN), and levée en masse, a policy innovation that facilitated recruitment and staffing of French military forces in the late 18 th century. Although these common cases might seem very different, we show that our framework applies to both in ways that should build confidence in our approach.

Divergent definitions
We begin by evaluating the literature on military innovation to understand current definitions. As others note, this field has grown in breadth and depth. 4 Given the size and scope of this literature, we begin with a limited sample of almost 100 texts that explicitly examine military innovation, and that the field views as such. To this end, we selected texts mostly based on their inclusion in two review articles published in in The Journal of Strategic Studies. 5 Research assistants examined the texts for 1) their definition of a military innovation, and 2) the military innovation cases looked at. 6 We then analyzed each definition, locating common themes and points of divergence. Drawing texts from two review articles on military innovation does introduce selection bias. However, given our goal of evaluating the similarities and differences in military innovation definitions, this type of selection bias should work against our purpose, making any finding more reliable. If we cannot find common ground between definitions in this limited sample, there is a more convincing case for a new path forward. In addition, by mostly focusing on articles referenced in these review articles, we limit our study to articles and books that explicitly discuss military innovation. While this selection leaves out some articles on very closely related topics, it also biases against our findings.
Including more articles on closely related topics would likely introduce even more definitional and topical variation. 7 Appendix Table 1 and the appendix  list of texts detail this further. Our review revealed broad areas of divergence across existing definitions of military innovation and related concepts. What do scholars agree upon? Not much. Military innovation is largely portrayed as a change in how militaries fight, relative to existing ways of war. For some, this change must be complete, requiring 'abandonment of the old' to be considered an innovation. 8 For others, innovations combine and utilize existing technologies and techniques in new ways. 9 While most scholars showcase the degree to which militaries, as organizations, have the capacity to implement changes -there is divergence regarding whether such change is applied to military doctrine, strategy, and/or tactics, and/or to exploit a given technology. Some scholars emphasize the role of political goals and national strategy in determining what 'counts' as an innovation. Others explicitly define military innovation as a process. This process can be treated broadly, or with an emphasize on the various stages. 10 Another area of divergence is the direction and location of the innovation process -whether an innovation occurs horizontally, from the bottom-up, or though adaptation. 11 Finally, there is a general commonality, though there are exceptions, in assuming military innovations must be successful in their application. These themes are not mutually exclusive categories. They are the common threads that draw together much of the literature. Indeed, many scholars incorporate several of these themes in their conceptualization of military innovation. The discussion below explores how these themes are distributed in the literature. 12 7 Some examples of notable scholarship on military innovation that were omitted from our sample due to the selection criteria include Geoffrey Parker,  , 1955-1991(Princeton, N.J.: Princeton University Press, 1993; Grissom, 'The future of military innovation studies', 907 12 Table 1 in the appendix further illustrates this distribution.

Military innovation involves change
Scholars generally agree that a military innovation, by definition, must involve a change in how militaries plan to fight, which necessarily alters the conduct of relevant military operations. However, assessments of the level of change required vary widely. Some portray military innovation as a 'break from the past,' rendering old ways of war obsolete. 13 From this perspective, military innovation involves 'a major restructuring' or significant change in military thought. 14 Rosen, for example, defines military innovation as a change so major that it involves a new approach to warfighting and, at times, the creation of a new combat arms branch. Such changes take place not through incremental improvements, but rather as an entirely new theory of victory. 15 Similarly, Cote conceptualizes innovative doctrine as a change that occurs on a large enough scale to require 'a military service destroy or thoroughly redirect an important part of itself.' 16 Hence, military innovations involve radical changes that destroy and replace the way of war that came before, for relevant military units, altering core tasks. 17 For some, innovative changes are so radical that they should be called 'Revolutions in Military Affairs' (RMAs Another perspective on change comes from scholars emphasizing the degree to which military innovations build on existing technologies, tactics, and doctrine. The influence that the Chinese invention of primitive grenades during the twelfth century had on the later invention of the gun, for example, demonstrates how inventions often require the reordering of familiar elements in novel combinations, rather than creating things ex novo. 19 Similar is Tai Ming Cheung's examination of 'indigenous innovation,' or Zizhu Chuangxin, i.e., innovation with Chinese characteristics. The term, a central principle of China's 2006 Medium-and Long-Term Science and Technology Development Plan (MLP), refers to the reassembling of 'existing technologies in different ways to produce original innovations.' 20 Here, the emphasis is on technology adoption, rather than technology creation. Military innovation occurs in this framework when foreign and domestic technologies and knowledge are improved upon and assimilated.

Innovative change requires organizational realignments
Scholars generally agree that militaries, as organizations, must change for innovation to occur. Innovation can alter how components of a military organization relate to the enemy and to each other, often requiring the creation of new operational procedures. 21 Much of the existing scholarship highlights the role of organizational frameworks as primary agents of military change. 22 Indeed, militaries share some similarities with other types of organizations and, like businesses, depend on the intersection of technological and organizational resources. 23 Much of the literature mentions a military's organizational capacity to exploit a given technology, tactic, or doctrine, explaining the presence (and absence) of innovation as a result of the broad structure of organizations -pointing to their hierarchy, cultures, and resistance to change. 24 Such characterizations of military innovation tend to treat technologies and tactics that have no impact for organizational strategy or structure as minor military changes, not military innovations. For example, Farrell and Terriff argue that shifts in U.S. Army tactics in Western Europe during World War II are not military innovations because they did not involve organizational change. 25 Many of these definitions lump doctrine, strategy, tactics, and organizational structure together, often in contrast with technology. The components of a military organization's stated roles, missions, and force employment structure are certainly linked, but by no means synonymous. Moreover, their role in the innovation process may vary, depending on the military change at hand. For example, while change in military doctrine is sometimes considered part of a military innovation, it is also sometimes treated as an innovation in its own right. 26 For others, doctrine represents organizational context that permits tactical and technical innovative changes to occur. The set of principles, constituting a military's doctrine, inform the 'theory of victory' around which innovation revolves, involving 'an explanation of what the next war will look like and how officers must fight if it is to be won.' 27 For Giese, this understanding of victory leads militaries to 'solve current or projected military challenges or threats as defined by the national strategy.' 28 Lock-Pullan condenses new ways of war, ideas about how organizational components relate to the enemy and each other, operational procedures, and critical military tasks into 'a range of ideational and structural changes.' 29 While we agree that military innovation requires a change at the operational level, the change need not include doctrine. 30 As we explain below, innovative formations of new tactics can (and do) take place at the small unit level.

The role of technology
Our survey finds a common, though not always explicit, tendency to focus on technical changes. This is clearly the case for research on 'the weapon which is ultimately deployed.' 31 Innovations are often viewed as tangible weapons and weapons systems that can be clearly described and evaluated. Indeed, the development of novel weaponry often relies on technological advancement. However, others point out that innovative changes in conduct of warfare can be both technical and tactical in nature, emphasizing the degree 26 Barry R. Posen to which major changes institutionalized in technologies constitute innovations in their own right, distinct from innovations involving organizational change. 32 For many scholars, technical change plays a central role in the innovation process, usually in conjunction with organizational change. McIntyre notes that innovation requires a synthesis between novel technology and the doctrinal and organizational changes required to 'create a revolutionary effect' on the battlefield. 33 In other words, technological innovation alone does not have the 'self-sustaining momentum' to produce an effective military innovation. 34 Goldman and Eliason argue that there is a relationship between hardware and software. Hardware refers to the technology used to fight, such as artillery and bombers, and software refers to 'the organizational or human application component of an innovation or technology,' such as doctrine, tactics, recruitment, and training. 35 While technological change often accompanies innovation, alone it is rarely enough. 36 As the distinction between the invention of the tank and the adoption of combined arms warfare illustrates, often it is the non-technical components of change that are especially salient in military innovation. 37 For Adamsky, technology, or 'hardware,' often serves as an important initial condition, but innovation depends on the 'confluence of weaponry, concept of operations, organization, and the vision of future war.' 38 This relationship is one between the object (the technology) and its context (the broader military organization).
However, there is often a time lag between the arrival of a technical innovation and its further development as a useful military tool. Thus, there is a danger both in conflating technical invention and military innovation, and in overemphasizing the role of technology. For example, McIntyre locates the first significant strategic use of the internal combustion engine at 'the transfer of two French infantry regiments by taxi to save the Sixth Army and Paris in fighting along the Marne River in September of 1914.' 39 Similarly, while tank attacks occurred in battles like Cambrai in 1917, the first use of the mature innovation, sometimes described as Blitzkrieg, featuring combined arms, did not occur until World War II. Thus, how militaries use raw materials is crucial in determining the difference between technical invention and military innovation. Moreover, focusing solely on the technological components of a given innovation misses key elements of the innovation process.

Political purpose
Some military innovation definitions highlight the broader political purpose assigned to an invention, whether a new technology or an organizational change. Technology and the military strategy and tactics required to implement it on the field are then inextricably linked to the political and national goals at hand. 40 For Eliot Cohen, military innovation stems from the 'adaptation of the military instrument to political purposes.' 41 Similarly, Chad Serena defines an innovation as a 'break from the past that incorporates technological advances with national interests,' drawing from Watts and Murray's discussion of visions of future war which can depend on changes in military technology, weaponry, the international security environment, and national purposes. 42 These definitions of military innovation explicitly acknowledge the military's role in service of the state. Political objectives drive and direct innovative changes in the military as a means of achieving such goals. 43 Other definitions highlight the extent of politicization in the innovation process or even the innovation itself. Beard attributes the acceleration of ICBM production in the early 1950s to prodding and promotion from the Air Force R&D community, JCS commissioners and directors for ballistic missile development, congressional hearings on US and USSR ballistic missile development, and the 1957 Sputnik launch. 44 Essentially, the military innovation process often involves political direction, intervention, and advocacy. Innovative changes require a 'pattern of policy making' in which participating individuals and groups bargain with one another, making military innovation 'essentially political.' 45 40  Indeed, political will, both outside and within the military can be important in the innovation process. For example, funding changes can spur or stymie the invention and incubation of innovations. Moreover, after the initial development of novel technologies and tactics, the decision to adopt and implement a given innovation requires political will and, sometimes, persuasion. While the enhanced ability to generate military power that may result from a given innovation can certainly bolster national interests, the goal of military innovation is to increase military capabilities.

Bottom-Up, Horizontal, and Adaptation: Innovation by many names
Some definitions explicitly include innovations that occur from 'the bottomup' or horizontally, often describing them as adaptation. 46 Grissom points out that technologies and tactics created on the battlefield, such as the US Navy's UPTIDE antisubmarine program and German storm-troop tactics in World War I, illustrate field-developed solutions accepted into formal practices. 47 Unlike top-down models that trace the efforts of elites atop bureaucratic organizational structures to foster military innovation, bottom-up innovations are triggered at the field level. Bottom-up changes move upward through information sharing, acceptance of new ideas by military leaders, and the flattening of organizational structures. 48 Between-unit learning can also spur horizontal changes: Foley argues that new ideas are not produced 'from high command or from frontline up,' but rather spread between units. 49 Such approaches stress the unique nature of innovation processes occurring from the bottom-up and horizontally, especially in relation to existing topdown models of organizational change.
The direction of both an innovation's derivation and its use are sometimes, but not always, conceptually linked to changes described as adaptations. Dmitry Adamsky and Kjell Inge Bjerga note that, unlike top-down processes where 'military theoreticians imagine the future of warfare and outline new theories of victory,' adaptation is 'more inductive and reactive in its nature.' 50 While top-down anticipations involve explorations into the current character of war during peacetime, adaptation builds on 'the insights produced by battleground friction and on the lessons learned from the best practices'  , 1939-1943,' Military Affairs 48, no. 1 (1984 during wartime. 51 Not only are these processes complementary, but also they both fall under the umbrella of military innovation. Nina Kollars, however, demonstrates that such processes need not be delineated as top-down/bottom-up. Her analysis of soldier-led gun-truck adaptation to challenges in Afghanistan and Iraq demonstrates how ad hoc networks can deal with tasks at hand through processes of military change triggered at the field level, among civilians, and among DoD elites. 52 Other scholars differentiate adaptation from innovation, noting the relationship between these phenomena but also their differences. Williamson Murray argues that adaptation and innovation take place in a different environment. Like Adamsky and Bjerga's distinction between anticipation and adaptation, Murray points out that while adaptation occurs during wartime (when drivers like technological advances and operational necessity are privileged), innovation occurs during peacetime. 53 Farrell and Terriff delineate between the two on the basis of the degree of change. They argue that while military innovation involves a novel, large-scale change institutionalized in doctrine, organizational structure and/or technology, military adaptation involves a change to existing technologies or tactics to improve performance, and may result in innovation over time. 54 Farrell later distinguishes between the scale of change and the degree of novelty and organizational disruption: military adaptations can involve large-scale change (occurring on levels ranging from the tactical to the strategic) but are less novel and organizationally disruptive than innovations. 55 However, Farrell avoids a clear distinction between military innovation and adaptation, treating the two as points on a scale. 56 While adaptations can involve adjustments and revisions to strategy, training, and tactics, supplementing forces, and retrofitting equipment, innovation often requires new strategies, doctrines, operational approaches, and equipment. From this perspective, innovation is one of multiple pathways through which military change can occur. 57 Farrell's distinction between adaptation and innovation on the basis of the degree of novelty and organizational disruption shows that adaptation potentially represents the early stages of an innovation. 58 The emphasis on bottom-up innovation, horizontal innovation, and adaptation highlights a challenge -how to distinguish military innovation from other terms used to describe changes in how militaries operate. 59 In the literature, terms such as adaptation and evolution can be equated with innovation, treated as a separate but related phenomenon occurring in a specific environment, or presented as a precursor to innovation. 60 Moreover, there is a significant overlap between innovations that might be considered bottom-up and topdown, or an adaptation on the basis of size, novelty, or organizational disruption.

Innovation as a process
Some definitions refer to innovation as a process of conceptualization and implementation, including the debut of hardware (e.g., technology) and software (e.g., doctrine, tactics, etc.),and their subsequent international diffusion. 61 For example, Michael Armacost tracks innovative change from research and development (R&D) to the incorporation of finished hardware. 62 Such definitions characterize innovation as a military change that emerges over time and several stages. Thomas Mahnken demonstrates how military institutions innovate in three distinct, yet often overlapping phases: speculation, experimentation, and implementation. 63 Others focus on a particular stage within this process. For example, Adamsky examines the intellectual activity that takes place during Mahnken's initial speculation phase. Here, 'military innovators identify novel ways of solving existing operational problems and of exploiting the potential of an emerging technology,' and experts realize the 'conceptual and organizational innovations that new technology can put into motion'. 64 Indeed, this early stage, when the tactics that become an innovation are invented, is often the focus of discussions of bottom-up and horizontal innovation, and adaptation. 59 As we discuss below, this challenge is further illustrated by the distinction (or lack thereof) between military innovations and RMAs. 60 This continues to be the case in more recent scholarship. Lindsay argues that 'user innovations' in Information Technology ( Arguably, even analyses that do not explicitly delineate between innovation stages can be considered from a process-driven approach. For example, when Grissom distinguishes between top-down and bottom-up innovation in the case of the German 88 mm Flak anti-aircraft cannon (the Flak 18/36), he is describing the process by which an innovation initially enters the bloodstream of a military organization, i.e., Mahnken's speculation phase. 65 Grissom traces the application of the Flak 18/36 as an anti-tank weapon to improvisation during the Spanish Civil War when a Luftwaffe battery commander decided to turn his guns on Republican Soviet-made BT-5 tanks, despite rejection of the tank-killing potential of the Flak 18/36 by experts in Berlin. The results from Spain soon spread to the anti-tank community in the German Army, proving useful in the 1940 campaign in France as a counter to French Char-1bis and British Matilda tanks, by Rommel's Afrika Korps in Halfaya in 1941, and in the east against Soviet T-34 and JS-1 tanks. 66 The distinction between and characterization of military innovation process stages requires further clarification and consensus. Mahnken's initial speculation stage begins with 'novel ways to solve existing operational problems or exploit the potential of emerging technology,' followed by experimentation. 67 The second stage requires 'the existence of an organization charged with innovation and experimentation.' 68 This conception of experimentation is primarily concerned with top-down testing and war-gaming by the defense industry, think tanks, and war colleges. However, as we discuss below, bottom-up and horizontal learning may apply here as well. Lessons learned from the application of tactics and/or technologies in wartime can influence the likelihood that such changes will be applied more widely. In other words, top-down experimentation may not be the only way an innovation gains influence within a military organization. Indeed, we argue that the subsequent stage -implementationis where organizational impetus and application is far more salient. Our proposed framework further clarifies the delineation between these stages.

Must an innovation result in battlefield success?
The literature shows clear conflation -both tacit and explicit -between the definition of an innovation and success of that innovation on the battlefield. 69 For example, Posen defines doctrinal innovations in terms of their integration with strategy and 'likelihood of victory or defeat.' 70 Indeed, several definitions in the universe examined for this article equate innovation with greater military effectiveness. For example, Adam Jungdahl and Julia MacDonald define military innovation as resulting 'in an improvement in overall military effectiveness.' 71 Thus, policies or technologies that are 'counterproductive . . . are thus not considered innovations.' 72 The operationalization of the RMA literature suffers from a similar weakness: the wide variety of delineations of RMAs are unified by their connection with military victory, or that only by speeding up technological, tactical, and doctrinal change, can battlefield success be ensured. 73 Similarly, implicit in much of the scholarship on military effectiveness is the understanding that more innovative militaries are more likely to succeed. 74 Defining an innovation as successful for military operations is methodologically problematic because it conflates whether a military institution changes in some way, and whether that change leads to greater military effectiveness, which can depend on many other factors. 75 A range of intervening variables may influence whether a given resource or capability produces battlefield outcomes. While the character of an innovation may influence outcomes, locating such effects requires distinguishing between the capability itself, and the ability of an organization to effectively translate military power into battlefield success. A new way of warfare is not synonymous with the effectiveness with which an innovation is utilized. Thus, separating the definition of an innovation from its success is a better approach. As described below, our definition requires novel force deployment methods and new organizational structures -with the promise of a significant and measurable increase in military effectiveness. 76 In other words, while the outcomes of actually using an innovation are of great importance to scholars and policymakers alike, having an innovation and using it (skillfully or unskillfully) are not the same.

So what is a military innovation? Promise and process
Overall, these diverse themes highlight existing challenges to analytical clarity in studying military innovation. a military innovation has occurred, and often use other terms -such as adaptation and evolution -synonymously with innovation. Moreover, we note a general lack of clarity regarding the distinctions between doctrine, strategy, and/or tactics and their relationship with the broader structure of military organizations, as well as a tendency to equate technological invention with military innovation. Many scholars also fail to distinguish between different steps in the innovation process. Finally, we challenge the assumption that military innovations must be successful in their application.
We define military innovations as changes in the conduct of warfare designed to increase the ability of a military community to generate power. This definition highlights several things. First, 'changes in the conduct of warfare' does not necessarily require doctrinal change, but it does require change at the operational level of war. While doctrine can certainly function to provide 'rules of thumb' that simplify 'complex operational calculations,' this need not be the case. 77 Moreover, as we will expand on below, while innovative changes can be small in size and scope, they must be considered from an operational level to be adopted. Second, 'military community' refers to the specific community of interest, which could be the entire military organization, but could also be a narrower area. For example, the US Marine Corps was the relevant community of interest for amphibious warfare, and the Navy was the relevant community for carrier warfare. Thus, while some changes in the conduct of warfare, such as the adoption of a system of mass conscription, are relevant across military forces more broadly, others can occur within a more contained community -such as a military service. Third, the phrase 'designed to' means that at their core, innovations might have only limited success in improving the ability of militaries to generate power. Military power is not synonymous with war outcomes, such as victory. As we discuss below, states vary in their ability to effectively marshal military power into battlefield success. Put simply, military innovations hold the promise of enhancing military power, but whether or not they end up doing so is not a requisite for qualifying as an innovation.
This definition also refers to the outcome of a broader process -which highlights the root of a great deal of confusion in the innovation literature. In other words, military innovation is both a process and an outcome. should not be conflated with the innovation process itself -i.e., what is being explained. Indeed, this focus on agency may distract from locating a clear and cohesive framework of miltiary innovation. Given this confusion, we build on existing accounts of military innovation as a process with several stages, to locate a common framework as summarized in Figure 1. The first stage involves invention -the creation of new technologies, the first application of an existing technology to a particular military operational problem, or the formation of new tactics, potentially even at the small unit level, for the application of military force. The formation of new tactics can involve attempts to apply recently invented or modified technologies but does not necessarily have to. Thus, the creation of the tank by the British Army, with the first 100 tanks produced in February 1916, represents the invention stage of an innovation. Another example of the invention stage is Roger Bacon's gunpowder recipe in 1267, which resulted in the appearance of cannons on the European battlefield in significant numbers in the 14 th century, and the lengthening of gun barrels to increase muzzle velocity and accuracy. 78 The second stage is incubation, or the process by which an initial invention, whether a tactic, a technology, or both, gains status and influence throughout the first-moving military. Usually, incubation takes years. This can happen through a bottom-up process or through a more traditional topdown process. The example of carrier warfare involves the use of the carrier as a mobile airfield for strike operations and establishing sea control. The incubation phase for carrier warfare occurred after the invention of the HMS Furious by the British Navy in 1917 and included experimentation by militaries around the world with carriers in the 1920s, 1930s, and early 1940s. Bottom-up experimentation by Captain Reeves in the early 1920s, tabletop exercises in the 1920s and 1930s, and advocacy through the Naval Aeronautics Bureau all contributed to shifting attitudes in the U.S. Navy  78 Krepinevich,'Cavalry to Computer',32. such that the carrier was envisioned as a mobile airfield, rather than a spotter for the battleship. Thus, incubation is a critical phase in the innovation process, and one that can occur at the grassroots level.
The third stage of military innovation is implementation. In contrast to the previous stage, where bottom up processes operate to nurture and develop technologies and tactics, implementation throughout a military is almost necessarily top-down. Here, political will (whether external to or within the military) leads the relevant community of interest (generally a segment of a military service such as the submarine force, an entire military service such as the Navy, or the military as a whole) to adopt the innovation. The possible drivers of such 'will' are varied and, unsurprisingly, at the center of much the military innovation literature, serving as an important aspect of the innovation process. It is at the point of mass adoption by the first moving state, which becomes capable of using the innovation as part of its operations, that implementation occurs. 79 The implementation stage distinguishes this approach from the work on bottom-up innovation or adaptation. Grissom and others describe where the idea for a military innovation comes from (stage #1: invention), and how a military determines whether a potential innovation is worth adopting (stage #2: incubation). For something to be a military innovation, it has to spread beyond the unit of invention, and be adopted throughout the community of interest within a military. 80 Returning to the carrier warfare example, while it was the British military that initiated the incubation of this innovation, it was the Imperial Japanese and US Navies that implemented the innovation. Grissom's description of bottom-up innovation is akin to the experimentation conducted by the U.S. Navy in the late 1920s and early 1930s. 81 Adoption by an entire relevant part of a military organization is the action that turns something into a military innovation (presuming all of the other definitional components are met). The process of adoption is inherently top down, generally involving changes in doctrine and tactics, if not something even broader. Thus, Grissom's key contribution -bringing forward the way grassroots processes can generate innovation -slots into the 'invention' or 'incubation' phase of the overall military innovation process. However, it is not possible for a military innovation to be grassroots or bottom-up at the implementation stage. The decision to adopt a given innovation across the relevant community of an entire military organization, from both a financial and organizational standpoint, is an inherently top-down process. In other 79 By 'first moving state,' we mean the state where the military innovation was first invented, incubated, and implemented. More than one state can be a first mover -i.e., introduce innovations at the same time. Horowitz words, at the very point at which an innovation is adopted, it ceases to be grassroots. Even innovations that arise from bottom-up experimentation require some degree of top-down adoption, indicating an inherent overlap in innovation direction.
After adoption, many military innovations diffuse and spread, to other military organizations. In the clearest theoretical form, a country invents, incubates, and implements on its own. Other countries then observe the innovation and go through the process in a different way -with the knowledge of how the first mover has acted and its degree of success. Military innovations often emerge in periods when multiple countries are working on similar capabilities. Each country observes parts of a military innovation through the lens of its own experience and what it can observe of and learn from the processes, actions, and experiences of others. A country may be able to skip or short-cut stages, depending on its bureaucratic process and prior progress. Moreover, as other military communities seek to emulate an existing military innovation, they will often modify the innovation to fit their own circumstances and goals. For example, Prussian analysis of Napoleonic levée en mass led to their adoption of a related conscription system in the 19 th century. 82 In other circumstances, components of an existing innovation may be emulated and altered to produce entirely new innovations. To return to an earlier example, the invention of the gun required the use of the very same constituents that went into the making of Chinese grenades during the twelfth century. Reversing the use of the very same powder, stones, broken porcelain, and iron bullets that filled the paper or bamboo tubes of grenades, and adding a touchhole, allowed the materials to be fired. 83 To summarize, military innovation is a process that begins with invention (in the broad sense of the word), includes a (possibly long) period of incubation in which the invention is ultimately seen as something important, and ends with the top-down adoption of the invention. Often this process is followed by the diffusion of the innovation across other communities of interest. Much of the existing debate about military innovation focuses on key drivers that 'kick off' the innovation process. Such hypothesized drivers of military innovation may operate at different 'points' in this process: the creation of a potential capability, the incubation period of discussion and adaptation, and the causal process through which that capability is adopted. The failure of much of the existing literature to clarify the point of the innovation process at which hypothesized drivers of military innovation operate may help explain variation in research conclusions concerning what makes military innovation more or less likely at different points in time. Calculated comparison across specific points of the innovation process is a fruitful area for future research in the field.
Additionally, while the impetus for military innovation is always the promise for something better, there are many examples of inventions that have failed to become military innovations, as well as innovations that have failed to translate into military power. Often new ideas or technologies are considered unworkable or irrelevant at early or later stages in the process and halted. Moreover, the innovation process need not occur linearly. There are examples of accidental innovations, or those that borrow and build from existing frameworks to create something new. 84 For example, while one military organization might struggle to experiment with a novel invention on the battlefield and fail to adopt it, others may learn from the experience and the mistakes that were made and successfully utilize the invention in new ways. By locating a common framework, non-conforming cases are easier to locate, compare, and investigate further. In other words, a process-based approach not only allows us to organize and compare innovation cases, but also to consider when and how deviations occur.

Applying our approach
How does our approach apply to the universe of existing cases in research on military innovation? Grissom argues that despite a clear dissonance in the definition of military innovation, in practice scholars gravitate towards cases that share a clear set of attributes, which yields a 'consensus (if tacit) definition.' 85 However, we found substantial variation across the 60 different cases of military innovation in the 79 books and articles we examined. This variation demonstrates the wealth of scholarship in the field and the range of possible cases for analysis, but it also challenges analytical parsimony. These findings support Griffin's concerns regarding the subsequent challenges of falsification and the magnification of selectivity biases across studies of military innovation: 'the more case studies, the less selectivity when applying them.' 86 Indeed, by failing to clearly delineate what constitutes a military innovation, the universe of cases for scholars seeking to develop explanatory models of innovation remain unclear, undermining the credibility of the field. 87 Figure 2 charts the cases examined in the literature we surveyed. While some cases, such as tank warfare, are purely military, others involve dual use technologies, such as railroads and information systems. Some, like the Napoleonic military system, involved large macro-social changes, while others, like nuclear weapons are technological in character. 88 Notably, many 84 Cheung, 'The Chinese defense economy's long march from imitation to innovation' 85 Grissom, 'The future of military innovation studies', 907 86 Griffin,'Military innovation studies',210 87 Ibid, 211 88 Goldman and Eliason,Introduction,24 of these innovations developed into layered systems -see for example the development of carriers to include defensive systems which include guidedmissile destroyers and last-resort weapons -that combine the new with the old (e.g., delivery of precision-guided munitions via pre-existing platforms).
The profusion of 20 th century cases highlights the lack of consensus regarding what constitutes an innovation. Many of the cases listed in Figure 2 correspond to developments in nuclear and information technology, but how they should be grouped across time and space remains disputed. In short, it is unclear where the relevant 'revolutions' begin and end. 89 Some scholars treat entire wars as 'a case,' often pointing to a moment where one step in the innovation process took place. For example, the 1973 Yom Kippur War was often examined as an illustrative case. 90 Here, Israel developed novel force planning processes to cope with doctrinal and technological surprises, such as Egypt's use of anti-tank weapons in the Sinai. 91 While some scholars treat this case as an example of Israeli adaptation, 92 others emphasize its influence on vision for future warfare, defense system requirements, and the acquisition of new technologies in Israel, 93 as well as the United  States. 94 Such cases highlight the broader tendency to focus on: 1) one stage of the innovation process -specifically, in this case, the debut or diffusion of an innovative change, and 2) the drivers of this process (i.e., wartime).
Of this universe of cases, which are the most commonly examined in analyses of the causes and consequences of military innovation? In other words, are there cases where there tends to be broad agreement surrounding their 'innovativeness'? Figure 3 charts the citation frequency of the innovations examined in the literature we survey. The most frequently cited cases were nuclear war, unconventional war, and counterinsurgency. Others often analyzed include interwar revolutions such as those in mechanization, aviation, and information, armored warfare, blitzkrieg, carrier warfare, air warfare, guided missiles, and counterterrorism. These most-cited examples are areas where the literature appears to have reached a tacit consensus, and where we seek to illustrate the utility of our proposed analytical framework.
For many of the frequently cited cases, the application of our framework is straightforward. The adoption of the aircraft carrier as the central surface platform of a Navy for airborne strikes demonstrates, as a plausibility probe, how treating innovation as a process rather than a point more accurately captures innovation emergence. As described above, there were clear and distinct invention and incubation periods for carrier warfare. The invention of the technology occurred in 1917 with the British deployment of the HMS Furious, which then began the incubation period as navies attempted to determine whether and how to use and prioritize aircraft carriers. Following two decades of experimentation by the United States, Japan, Great Britain, and others, the United States formally adopted what most observers now consider modern carrier warfare through PAC 10, the fleet orders of 1943, which institutionalized the carrier task force as the Navy's key striking force and marks the implementation phase of the carrier innovation. 95 The adoption of carriers into doctrine in various forms by leading powers over the years and decades to follow represents the diffusion phase. Great Britain, despite inventing the aircraft carrier, viewed it as subsidiary to the battleship in the Royal Navy. It was not until the end of World War II, when the British Navy turned to the United States for operational training, that they adopted carrier warfare. 96 For other innovations, however, the timing of the innovation 'stages' is less obvious. Levée en mass, while a classic case in the literature, is rarely examined closely as a military innovation process. Where did the impetus for mass conscription come from, and how did the vision differ from its practice? Counterinsurgency, one of the most frequently cited cases in the literature, is also less straightforward. Its 'principles' were around long before the U.S. military applied them in the field -is this a case of bottom-up innovation? Is population-centric counterinsurgency (COIN) simply the rehashing of earlier operational concepts for the 21 st century? The long history of learning and relearning lessons from the Philippines, the Caribbean Islands, the irregular campaigns of the Second World War, and to the Vietnam campaigns in the 1950s and 1960s makes it difficult to locate a discernible innovation process.
Moreover, these cases also highlight many of the divergences across the military innovation literature discussed above. Levée en mass is considered a revolutionary case, involving the confluence of not only political and social changes but also tactical and technological advances. Indeed, this case introduces a great deal of interlinking and temporally spaced drivers of such changes, highlighting themes of political purpose and organizational capacity evident in the literature we survey above. While COIN tactics are often cited as examples of changes arising from the bottom up, our approach clarifies the stage at which this was the case, as well as where it was not. Finally, both cases illustrate that salience of military innovations that do not take the form of countable, tangible weaponry.
In the appendix, we apply our analytic framework to these two illustrative cases of military innovation in substantial detail. We stress that these cases are meant to be illustrative, rather than a rigorous comparative analysis. Nonetheless, the results strongly support our approach. We find that it took time for the ideological claims of the 1793 levée en mass to be translated into practice. Conscription would require industrial resources, a strategy to prevent desertion, and the creation of new promotion patterns. It would take years for a system of annual recruitment to be institutionalized under Napoleon Bonaparte and then diffuse across Europe, with varying results. COIN tactics similarly took time to go from invention to incubation. Despite the long legacy of population-based approaches to counterinsurgency, the U.S. military would largely ignore such approaches until after the Vietnam War. It would take experimentation with these approaches in the field, followed by the publication of a field manual, for the innovation to be adopted.

Conclusion
Military innovation is a key driver of military power, and thus a vital area of security studies research. However, such research has been stymied by a literature that lacks a common definitional ground. We propose a new path forward that can incorporate a range of innovations -from those involving large-scale technological changes, such as carrier warfare, to those featuring operational changes, such as such as levée en masse and COIN -and include the stages of the innovation process. Our approach provides a clear umbrella for the study of military innovation, without favoring any potential explanations for why these innovations occur. There are significant debates in the field about the relative importance of external threats, promotion patterns, mavericks, culture, organizational politics, and other factors as drivers of military innovation. Our definition is, conceptually, agnostic about the drivers of innovation, allowing future research to compare apples to apples when presenting potential explanations.
By treating military innovation as a process, scholars can more accurately describe how and when innovative changes occur. Military innovations do not spring forth fully grown. They develop over time, as an initial idea or technological breakthrough becomes subject to experimentation and war-gaming, and thereby eventually results in innovation. Our approach also helps redefine what is and is not a military innovation. A clearer notion of what is included and excluded can bring more clarity to the analysis of military innovation by scholars and practitioners alike. Militaries around the world are constantly navigating questions about emerging technologies, such as artificial intelligence, and if and how they should alter parts of their militaries to integrate these technologies. Thus, this approach has important implications for how military communities evaluate their processes for innovation and organizational change.
Our approach also helps explain long running discussions over whether it makes sense to think about population-centric counterinsurgency, in various points in time, as a military innovation or an adaptation. John Nagl's account of the development of counterinsurgency doctrine in Malaya, Vietnam, and Iraq is cited as an example of a bottom-up explanation for military innovation. 97 However, our framework highlights how the 'bottom-up' nature of COIN occurs during a specific point in the innovation process -the incubation stage.
Finally, describing the military innovation process more accurately will also improve the ability of the security studies community to coherently examine how emerging technological and tactical changes may shape the future of warfare. There is a temptation to over-focus on technological change, because it is the easiest to observe in most cases. The risk for scholars, as well as militaries, is what McMaster refers to as 'the vampire fallacy,' or 'the belief that technology and firepower are sufficient to achieve lasting strategic results in war.' 98 Our approach helps mitigate techno-optimism by explicitly clarifying that technological change is only the first part of process that results in a military innovation. Thus, as emerging technologies come online, this approach could help the security studies community more accurately characterize the extent to which changes in how militaries fight are or are not genuinely transformational.