Hew Strachan, the preeminent military historian at Oxford, stated in a lecture delivered in 2006 that one of our most serious problems today is that we do not know what war is. He put his finger on a critical shortfall in Western thinking about security:

If we are to identify whether war is changing, and—if it is—how those changes affect international relations, we need to know first what war is. One of the central challenges confronting international relations today is that we do not really know what is a war and what is not. The consequences of our confusion would seem absurd, were they not so profoundly dangerous.1

The larger problem is that the U.S. has a strategic culture that does not appreciate history or strategy, nor does it devote sufficient attention to the breadth of adversaries facing it and the many different forms that human conflict can take. Many current critics of U.S. policy or strategy in the Middle East or Asia bemoan the aimless state of strategy and policy. While there are deficiencies in U.S. planning and strategy processes, the larger intellectual challenge is a blinkered conception of conflict that frequently quotes the great Prussian soldier Clausewitz without realizing the true essence of his theory and how it applies to the ever evolving, interactive phenomenon we call “war.” Moreover, the U.S. national security establishment too often fails to understand opponents, their strategic cultures, and their own unique conceptions of victory and war.

Current perceptions about the risks of major war, our presumed preponderance of military power, a flawed understanding of irregular war, and our ingrained reliance on technological panaceas like precision-guided munitions (PGMs) and drone warfare make serious defense planning ever harder. This misunderstanding afflicts the military as much as it does political elites and the general public. At least three consequences can be expected from a flawed grasp of contemporary conflict:

  • Unreasonable political and public expectations for quick wins at low cost,
  • An overly simplistic grasp of the application of blunt military power and what it will supposedly achieve, and
  • Naïve views of both adversaries and the context for conflict.

As our own recent history shows, however, the reality is much more complex. War is seldom so clear-cut, and “victory” is far more elusive in reality. The vast majority of conflicts are seldom as precise or as free of casualties or political frustrations as we tend to remember. We prefer Operation Desert Storm (1991) as a simple and satisfying war. It pitted good against evil, and its conclusion was decisive, albeit not as decisive as World War II. But most conflicts are messy, relatively ill-defined in scope and by objective, with an array of actors, and unsatisfying in outcome.

The conflict spectrum includes a range of activities to which students and practitioners of war refer when attempting to characterize a given conflict by participants, methods, level of effort, types of forces, levels of organization or sophistication, etc. As should be expected in any attempt to define aspects of something as complex as war, there is ample debate over characterizations and definitions, whether one form of war is more or less complex than any other, or whether war can be so neatly categorized as to subdivide it along a spectrum in the first place. Debates over supposedly “new” and generational wars are common today in academic circles, and the prevalence of irregular wars is increasingly recognized.2

Generally speaking, large-scale conventional war is rather easy to understand. The term evokes images of tank battles, artillery barrages, planes bombing targets, and large masses of men clashing in battle as depicted in countless movies and books. Similarly, discussions of counterinsurgency (COIN) and stability operations often need little clarification given U.S. involvement in such operations for nearly 14 years in the larger Middle East and Central Asia regions.

Over the past decade, however, other terms have entered the lexicon of national security and defense analysts as they have attempted to describe conflicts that fall short of conventional war but are something substantively different from COIN and stability operations. What follows are descriptions of these other types in order to draw out and clarify the range variation of conflicts we face in the contemporary security environment.

Gray Zone Conflicts and Ambiguous Warfare

Recently, there has been a good deal of discussion about “gray zone” conflicts. This term appears in the 2010 Quadrennial Defense Review (QDR) and has also been reflected in official Japanese government documents.3 The term captures deliberate multidimensional activities by a state actor just below the threshold of aggressive use of military forces. In such conflicts, adversaries employ an integrated suite of national and subnational instruments of power in an ambiguous war to gain specified strategic objectives without crossing the threshold of overt conflict. Adversaries may employ proxy forces to increase the level of military power being used without losing deniability.

Examples of recent gray zone conflicts include China’s assertive behaviors in the South China Sea, sometimes referred to as “salami slicing tactics” by which they carefully erode the existing international order and attempt to change the norms of international behavior and assert their preferred reinterpretation of existing laws and rules of the road.4 China’s diplomatic assertions, information announcements, and deliberate use of fishery/maritime security forces to assert sovereignty in and around contested shoals and islands in the Pacific constitute a good case study in deliberately deniable acts of aggression. Russia appears to be following similar tactics in numerous countries, a form of “Simmering Borscht” by Russian officials seeking to extend Moscow’s sphere of influence without triggering an armed response by Western Europe or the United States.

Both cases clearly demonstrate that states that lack the capability to gain their strategic objectives with conventional means can find ways to erode the international order or to paralyze responses by other states through ambiguously aggressive actions. They also demonstrate that states that do possess the necessary conventional means may determine that their objectives can be achieved without resorting to conventional war and that this “gray zone” of war may actually suit their purposes better. These countries seem to recognize that U.S. strategic culture conceptualizes war and peace as two distinctive conditions—a perspective that is not held by other cultures.

Gray zone conflicts are aimed at a gap in our intellectual preparation of the battlespace and a seam in how we think about conflict. As noted by defense policy veteran Nadia Schadlow:

By failing to understand that the space between war and peace is not an empty one—but a landscape churning with political, economic, and security competitions that require constant attention—American foreign policy risks being reduced to a reactive and tactical emphasis on the military instrument by default.5

Senior U.K. officials have articulated the need to counter what they call ambiguous warfare. The relevance of this term can be seen in Russia’s seizure of Crimea, as Moscow’s planned actions were deliberately enacted to obscure attribution to Moscow and to paralyze or delay Western responses. But Russia’s activities in eastern Ukraine, where over 7,000 fatalities and sizable battles have occurred, are anything but ambiguous: Russian forces, Spetsnaz advisers, armor, and artillery are employed there in direct support of Russian separatists. It is neither masked nor concealed.

The war in eastern Ukraine is not just a proxy war; it is a combination of advanced military assets with irregular forces, propaganda, and coercion of the civilian population. Vladimir Putin may elect to disavow these forces, promulgate new laws making any public notice of Russian casualties illegal, and cremate the bodies of his fallen soldiers to avoid revealing the depth and mounting costs of Russian involvement, but none of this makes the conflict anything other than a Russian operation.

Russia’s larger set of activities against the West do not involve warfare as the U.S. has traditionally defined it. Moreover, “warfare” connotes a defense-centric response or a principal responsibility in solely military terms. Thus, “gray zone” or “ambiguous conflicts” are better terms that convey the complex nuances of such conflicts.

Irregular Wars

Irregular wars can be fought by states but generally involve non-state actors using sub-conventional capabilities including ambushes, raids, and minor attacks. Existing U.S. doctrine defines irregular warfare as a violent struggle among state and non-state actors for legitimacy and influence over the relevant populations.6 U.S. defense efforts in irregular warfare can include counterterrorism; unconventional warfare; foreign internal defense; counterinsurgency; and stability operations that, in the context of irregular warfare, involve establishing or reestablishing order in a fragile state or territory.7

Irregular warfare is characterized by indirect and asymmetric approaches that avoid direct and risky confrontations with strong forces. The goal for an irregular force is to erode its adversary’s power, legitimacy, and will. Such conflicts are usually drawn out or protracted in time. They can include insurgencies, counterinsurgencies, terrorism, and counterterrorism. Modern cases of irregular warfare increasingly include activities that we traditionally characterize as criminal behavior, and transnational criminal organizations may be present in such conflict. The level of violence in irregular wars can be low but can flare quickly with attacks or acts of terrorism.

These conflicts are well above the more indirect and less violent levels seen in gray zone conflicts but below the threshold of conventional war where armor, artillery and airpower assets are employed with greater degrees of integration and violence between combatants. The Islamic State or Daesh represents the high end of an irregular adversary, with high levels of adaptability and increasing lethality.8

Terrorism is a subset of irregular warfare. Terrorism is often a label assigned to certain types of armed groups rather than an accurate description of their mode of war. The official definition found in Title 22 of the U.S. Code provides that terrorism is “premeditated, politically motivated violence perpetrated against noncombatant targets by subnational groups or clandestine agents.”9 It could be a tactic of a revolutionary movement, or it could be the strategy of choice for a small cell of zealots.

There is widespread consensus in the security field that the democratization of lethal means of conflict will embolden small networks or even individuals to greater violence.10 Not much more than a decade ago, several forecasters projected a new age in ultra or catastrophic terrorism in which terrorists would attempt to kill thousands of Americans in a single day.11 They were routinely ignored until 9/11. Politically motivated violence against innocent noncombatants has continued to evolve, with increasing numbers of large-scale attacks occurring in several ongoing conflicts, most of which are centered in civil wars. U.S. intelligence officials believe such conflicts (Nigeria, Libya, Yemen, Syria, and Iraq) constitute a major near-term threat to our interests.12

The past few years have seen a significant rise in terrorist attacks and fatalities.13 Much of this increase is connected to Islamic extremists.14 The U.S. government–sponsored National Consortium for the Study of Terrorism and Responses to Terrorism (START) reported some 8,400 terrorist attacks in 2012, with 15,400 fatalities.15 The aggregate of fatalities is also increasing, as these attacks produced more than 17,800 deaths and 32,500 injuries in 2013.16

In 2014, the number of terrorist attacks jumped 35 percent, to 13,500, while the number of fatalities soared 81 percent, to 33,000.17 The majority of these attacks (60 percent) occurred in five countries (Iraq, Pakistan, Afghanistan, India, and Nigeria), and almost 80 percent of fatalities from terrorist attacks also took place in five countries (Iraq, Nigeria, Afghanistan, Pakistan, Syria). Over 9,000 people were kidnapped, representing a 300 percent increase. The most significant increase was in large-scale attacks (those that kill over 100 people), which jumped tenfold from two to 20.18 (For the most violent states and global totals for 2014, see Table 1.)

Countries with the Most Terrorist Attacks in 2014

Al-Qaeda’s evolving but persistent threat is just one element in this projection.19 There is no doubt that the core of the old al-Qaeda has been transformed.20 Some analysts contend that it has a better strategy, deeper bench, greater resilience or dexterity, more appeal, and higher amounts of sanctuary than imagined.21 As START Executive Director William Braniff has noted, “groups generally associated with al-Qa’ida remain the most lethal groups in the world.”22 Worse, ISIS is competing with al-Qaeda for influence, assets, and recruits and is more nuanced in how it employs violence and combines terrorism, repression, and services.23

Violence is not limited to the Middle East or South Asia. Boko Haram, for example, is considered responsible for over 10,000 deaths since 2001. It was designated a terrorist organization by the U.S. Department of State in 2013. Recent congressional reports have highlighted this group’s linkages to al-Qaeda and potential for direct threats to American interests.24 Its leader, Abu Bakr Shekau, pledged allegiance to Islamic State emir Abu Bakr al Baghdadi in March 2015.25 Boko Haram’s grisly campaign includes a suicide attack on a U.N. building in Abuja in 2011, repeated attacks that have killed dozens of students, and the kidnapping of 250 girls in 2014.26

To help the reader, a construct for a spectrum of conflict is presented in Figure 1.

Hybrid Wars

Building on Marine General Charles Krulak’s depiction of future wars as the “stepchild[ren] of Chechnya,”27 U.S. Marine analysts identified trends suggesting deliberate efforts to blur and blend methods of war. This forecasted convergence evolved into a theory of hybrid threats.28 The projection was borne out by the example of Hezbollah in Southern Lebanon a few years later and appears to be relevant to other conflicts as well.29 Two Secretaries of Defense in the United States found the concept useful,30 and numerous other military leaders, including Chiefs of Staff of the Army and several Joint leaders, recognized that current “bins” were not matching up with contemporary conflict.31 Hybrid threats are now part of the lexicon used by the senior levels of the U.S. military in the Quadrennial Defense Reviews, in national-level intelligence reports on the future character of war, and in various top-level documents of other countries.32 Some European military analysts, pushed by Russia’s example, have also embraced the hybrid evolution as a feature of contemporary conflict.33

Spectrum of Conflict in Unconventional Warfare

The term “hybrid” reflects more than a cross-breeding or blurring of regular and irregular tactics. It was originally defined as involving “Any adversary that simultaneously and adaptively employs a fused mix of conventional weapons, irregular tactics, catastrophic terrorism, and criminal behavior in the battlespace to obtain desired political objectives.”34 The crime, socially disruptive behavior, and mass terrorism aspects of hybrid warfare should not be overlooked, but the fusion of advanced capabilities with the fluidity of irregular tactics is key and has been borne out repeatedly over the past decade. Hybrid theory is also seen in Russian campaigns in Georgia and Ukraine.35 In the Crimea, Russia demonstrated that it had learned from its performance in Georgia in 2008 and had sought more indirect and hybrid methods.36 This was hardly new or “ambiguous,” but it was effective under very unique circumstances. This led the Secretary General of NATO in Brussels to employ the term as well.

Putin is certainly not reinventing warfare, but a new generation of leaders, spawned within the KGB, are clearly applying long-standing Russian concepts of protracted conflict that are not well understood by Americans.37 The chief of Russia’s general staff noted in 2013 that “War and peace, are becoming more blurred. Methods of conflict have changed, and now involve the broad use of political, economic, informational, humanitarian and other non-military measures.”38 What some call the “Gerasimov Doctrine” is consistent with the trends identified by U.S. military theorists and the intelligence community about hybrid threats. For this reason, hybrid warfare is now an explicit discussion point at NATO and major European think tanks.39

It also applies to Iranian doctrine and exercises.40 Hybrid threat theory is most often tied to ground conflicts, but Iranian naval force investments and exercises clearly demonstrate that high-tech, swarming, hybrid war at sea is possible.41 Iran’s mixture of fast but lethal small boats, mini-submarines, mines, illegal seizures, advanced anti-ship cruise missiles, and threats to interdict vital oil lanes is very representative of a hybrid maritime threat.

Some analysts have recently conflated hybrid threats “with incremental approaches to remain below the threshold of intervention from the U.S. or our allies.”42 Such an extension of hybrid threat theory is understandable given the theory’s sourcing from Russian and Chinese writings, which deal with the fusion of various non-military tools (finance, propaganda, lawfare, etc.) with threats of force. However, as noted earlier, the “below the threshold” idea fits better with gray zone or ambiguous conflicts, which involve conflict activity short of violence. Hybrid threats ably combine various modes of fighting in time and space, with attendant violence in the middle of the conflict spectrum. Gray zone conflicts do not cross that threshold and use a different mix of methods, entirely short of bloodshed.

Unconventional Conflict

Some authors have advanced the concept that we need to reinvigorate U.S. capacity to engage in “warfare” with greater agility at lower levels short of war. Max Boot and Dave Maxwell have noted American deficiencies in responding to foreign sources of conflict that the United States used to deal with during the Cold War.43 They have refreshed George Kennan’s arguments from the 1950s for the institutionalization of U.S. capacity for political warfare, which Kennan defined as:

the employment of all the means at a nation’s command, short of war, to achieve its national objectives. Such operations are both overt and covert. They range from such overt actions as political alliances, economic measures, and “white” propaganda to such covert operations as clandestine support of “friendly” foreign elements, “black” psychological warfare and even encouragement of underground resistance in hostile states.44

Kennan’s definition of political warfare is misleading. His concept has little to do with warfare per se; it is largely about non-military efforts associated with subversion or counter-subversion. While these can have a political element to them, in terms of aiding political groups and factions, the range of efforts involved goes beyond the diplomatic and political sphere.

But there is little doubt that unconventional warfare and the types of techniques included in Kennan’s definition of political warfare are relevant to the 21st century.45 Unlike other forms of warfare in the proposed spectrum of conflict, unconventional warfare does not fit easily within a spectrum in terms of the scale of violence. Moreover, unconventional warfare can occur concurrently with other methods in both peace and war. Thus, it is depicted in Figure 1 as ranging across the entire spectrum, not just by the intensity of violence.

This concept would seem to have great merit as a response to both Russian and Chinese actions in gray zone conflicts, since neither state embraces the idea that war and peace are binary conditions. Both of them, as well as other strategic cultures, envision a more complex continuum of cooperation, competition, collaboration, and conflict. Moreover, many other nations do not organize their government institutions with the same black-and-white military and non-military distinctions as the U.S. maintains. There is evidence that some components of the U.S. military are devoting intellectual capital to this issue,46 and Congress has shown interest in assessing U.S. capabilities in this domain. By its nature, a U.S. capacity for unconventional warfare would involve the ability to develop and execute a strategy that tightly integrated measures needed to counter the subversion, propaganda, and political actions of gray area conflict short of actual warfare.

Experience with the Russians, both during the Cold War and more recently, suggests that the admixture of political/economic/subversive activity remains an element of their operational art and one that we would be well advised to begin studying so that we can counter it.47 For example, the information domain will be increasingly contested. Both states and non-state groups will exploit the Internet and other forms of social media across the conflict spectrum.48 We can expect to see cyber insecurity and information warfare attacks as part of any serious challenger’s portfolio, with such tools rapidly evolving to the point where they should be considered a “combat arm” of the unconventional threat.49

Limited Conventional War

To the right of hybrid conflicts on the spectrum, we next consider “limited” wars. These are generally fought between state actors using conventional military means but are bounded by such limiting considerations as geographic boundaries, types of targets, or disciplined use of force.

When considering objectives being pursued with military means, one man’s limited war is admittedly another’s total war. As an example, the U.S. invasion of Iraq in 2003 was conceived and executed within the limited category. Overthrowing Saddam Hussein’s regime by conventional force of arms was an absolute objective, and Hussein’s efforts to prevent its achievement made the war an unlimited event fought for survival, but the conduct of the war by the U.S. was highly disciplined in target selection, geographic setting, initial objectives, and the way in which military force was used.

Sir Lawrence Freedman has applied the term “limited conventional war” to describe the Ukrainian conflict,50 but there are two problems with this classification in this instance.

First, as a concept emanating from Cold War–era discussions of the application of nuclear weapons, it addresses Moscow’s objectives but says little about the details of Russia’s strategy or methods. In fact, most wars are inherently limited by objective or means of fighting. Clausewitz’s theoretical ideal of “absolute wars” is rarely pursued. Thus, the term has little intellectual value or granularity since it makes few useful distinctions other than stating the obvious: that Russia is not actively using the full range of its strategic arsenal. More particularly, it says little about Kiev’s perspective, as the dismemberment of Ukraine is hardly a limited matter for that government.

Second, limited wars are generally conventional wars, conducted by state actors that are relatively open about operating short of their full military capacity in pursuit of limited aims. This is something that, because of Russia’s deliberate ambiguity and opaqueness in its activities, is not terribly relevant or accurate with regard to the character of conflict in eastern Ukraine or the methods Russia is using to obtain its policy aims.

The challenge of characterizing any conflict aside, this remains a necessary and useful category to describe conflicts between regional powers or by a major power along its borders, if only because it facilitates informed debate on corresponding policies, diplomatic and political responses, and one’s own military efforts.

Major Theater War

After more than 20 years of peace support, stability, and counterinsurgency operations in Africa, the Balkans, and the Middle East, many in the security community have lost sight of the potential for major theater wars. In fact, a lot of pundits mistakenly believe that great-power competition and serious large-scale combat are things of the past. Sadly, they are wrong. There have been positive trends in reduced levels of interstate conflict for a generation, but several key conditions that buttressed that era of strategic stability are being eroded.

The prevailing American-led power structure has contributed to subdued levels of interstate conflict and war. However, that system and its attendant security are being challenged by major powers, abetted by a reduced U.S. presence in key regions and diplomatic affairs relative to the Cold War era and by some regional players who are building up or pursuing nuclear weapons and acquiring other destabilizing weapon systems. Alterations in the current power system by China’s significant economic development and rapid military modernization, or by Russia’s more militaristic approach to its security interests in Europe, the Arctic, and elsewhere, conceivably could produce circumstances in which great-power competition erupts into a war.51

Even academics favoring a less assertive foreign policy and a smaller U.S. military admit that “[h]istorically, transition periods marked by hegemonic decline and the simultaneous emergence of new great powers have been unstable and prone to war.”52 The emergence of rising powers generates armed conflict with the existing predominant powers.53 Major conflict can also be generated by fears of declining powers that may be inclined to take far greater risks to preclude losing prestige or influence. Russia’s actions during the past two years give some clues as to the potentiality for interstate war from a power that cannot resolve its lost capacity to sustain its status or that seeks to deflect public attention from a declining domestic condition.

Great-power conflict is never inevitable, but for evidence of a disturbing trend, it should be noted that while U.S. military budgets are being reduced some 25 percent in real terms, aggregate military spending in Asia is on the rise and is now greater than total spending in Europe.54 Moreover, spending by European allies of the U.S. is down sharply as they attempt to reestablish their economic growth while holding on to social safety nets.

Declines in the preponderance of U.S. power in the Asia–Pacific theater have reduced conventional deterrence, and China’s military expansion could accelerate instability. The United States is challenged to demonstrate that it retains the ability to conduct military operations in the Asia–Pacific region and fulfill its treaty obligations to its allies. This requires a military capacity—one that is growing increasingly suspect—to achieve two critical U.S. objectives: maintaining freedom of the commons (air, sea, space, and cyberspace) and limiting the potential for large-scale regional conflict through deterrence. The goal, one strategist noted, “is to leave everyone in Asia believing that when it comes to solving regional problems, there are better answers than the force of arms.”55

In addition to great-power competition, conflicts can be stoked by weak leaders exploiting sectarian tensions for personal political benefit or buttressing their legitimacy by appeals to nationalism. This can produce aggressive or irrational acts. Nationalist fervor can spin out of control, inflating fears or goals beyond cold calculations of national interest and political compromise, which in turn can lead to gross miscalculation and aggressive actions that increase the odds of conflict. The possibility that this might occur in Asia cannot be overlooked. Meanwhile, in Europe, Putin often exploits the deepest chords of Russian nationalism and Orthodox Christianity to buttress his melting political capital.56

The combination of decreased American engagement and military capacity with the overt aggressiveness of two authoritarian states that do not hesitate to flount accepted norms of international behavior is not helpful. The U.S. is facing the increased potential for major conflict between large states that have advanced and potent military capabilities. Any comprehensive assessment of the overall force size, capabilities, and readiness levels of the U.S. military should raise concerns about the country’s ability to handle such a major crisis, even noting that perceptions of American weakness can prompt militarized opportunism.

America has entered an era in which its technological advantage is rapidly being eroded and its military superiority is increasingly being challenged. This has led to calls from the Pentagon to energize efforts to seek a leap-ahead technology to offset its lost technical dominance.57

Given the high possibility of sustained small conflicts (gray, irregular, and hybrid), the potential incidence of limited and major conflict also increases, because any American Administration can find itself without adequate means to deter or defeat attacks from opportunists or aggressor states.58 Moreover, readiness funding levels to cover the full range of training tasks needed for the spectrum of threats for which the military must be prepared are lacking.

The world has enjoyed a holiday from major-power war for quite some time. The aggregate effect of America’s potent strategic deterrent, military preparedness, and robust alliances produced a long peace. All of these contextual conditions are now at risk as a consequence of sequestration and the West’s reduced willingness and capacity to take active measures to sustain an international order that was carefully designed and sustained to preserve peace. As former Pentagon official Dov Zakheim has observed, “The whittling away of American preeminence that we have witnessed over the past decade was not foreordained. It was the product of conscious choices….”59 We should consciously reset those choices to be better prepared for tomorrow’s conflicts.


The U.S. national security community should avoid narrow categorizations. The black-and-white distinction between war and peace, or traditional war and irregular war, makes for nice, simple boxes, but the real world is not so easily categorized. In fact, some adversaries seek to exploit U.S. paradigms and the gaping institutional seams that they create.

Rather, we need to embrace the fact that future opponents have their own ideas about how to fight, and they tend to mix and match those ideas with deliberate combinations of modes of conflict. Hard-wired and quaint notions of declared wars between states with symmetrically equipped armies and navies facing each other on defined battlegrounds are no longer helpful. The U.S. must expand its definitions and concepts beyond its history, cultural biases, and organizational preferences. Ultimately, its security is predicated upon its national security community’s being aware of the enduring continuities of war and possessing an adaptive ability to counter the many forms that warfare can take.

The United States faces adversaries capable of using strategies and techniques across the entire conflict spectrum. It must not give ground in gray zone conflicts if its interests are challenged. Europe and the Middle East today are a Petri dish of hybrid conflict,60 and the Defense Department’s current leadership team understands this evolving hybrid challenge.61 The U.S. needs to prepare for that, and reinvigorating its unconventional conflict capability will help.62 We should not lose sight of the reality that the “gold standard” for high-end conventional war is based on excellence in joint combined arms warfare.

Large-scale conflict between states is not a relic of history. The potential for interstate war still exists and is arguably increasing. It is the most demanding form of war with the most costly of consequences, and the U.S. is less prepared for it than it should be—a concern raised in the bipartisan Independent QDR Report, which found that the U.S. is seriously shortchanging its national security interests.63 Appreciating the broad range of challenges and threats we face is the first step toward recognizing a growing danger.

  1. Hew Strachan, “The Changing Character of War,” lecture delivered at the Graduate Institute of International Relations, Geneva, Switzerland, November 9, 2006, p. 2, http://www.europaeum.org/files/publications/pamphlets/HewStrachan.pdf (accessed July 8, 2015).  

  2. For an overview of the debate about generational warfare, see Global Insurgency and the Future of Armed Conflict: Debating Fourth-Generation Warfare, ed. Terry Terriff, Aaron Karp, and Regina Karp (London: Routledge, 2008). On the frequency and pervasiveness of irregular conflict, see Max Boot, Invisible Armies, An Epic History of Guerrilla Warfare from Ancient Times to the Present (New York: Liveright, 2013).  

  3. U.S. Department of Defense, Quadrennial Defense Review Report, February 2010, p. 73,
    http://www.defense.gov/QDR/QDR%20as%20of%2029JAN10%201600.pdf (accessed July 9, 2015); Japanese Ministry of Defense, Defense of Japan 2010 (Annual White Paper), p. 61, http://www.mod.go.jp/e/publ/w_paper/2010.html (accessed July 8, 2015).  

  4. For an excellent set of ideas about how to impose costs and counter coercive activities, see Patrick M. Cronin and Alexander Sullivan, “Preserving the Rules: Countering Coercion in Maritime Asia,” Center for a New American Security Maritime Strategy Series, March 2015,
    http://www.cnas.org/sites/default/files/publications-pdf/CNAS%20Maritime%20Strategy%20Series%20Capstone.pdf (accessed July 9, 2015).  

  5. Nadia Schadlow, “Peace and War: The Space Between,” War on the Rocks, August 18, 2014, http://warontherocks.com/2014/08/peace-and-war-the-space-between/ (accessed July 8, 2015).  

  6. U.S. Department of Defense, Irregular Warfare (IW) Joint Operating Concept (JCO): Version 1.0, September 11, 2007,
    http://www.dtic.mil/doctrine/concepts/joint_concepts/joc_iw_v1.pdDf (accessed July 9, 2015).  

  7. U.S. Department of Defense, “Irregular Warfare (IW),” Directive No. 3000.07, August 28, 2014, p. 1, http://www.dtic.mil/whs/directives/corres/pdf/300007p.pdf (accessed July 9, 2015).  

  8. Jessica Lewis McFate, The ISIS Defense in Iraq and Syria: Countering an Adaptive Enemy, Institute for the Study of War Middle East Security Report No. 27, May 2015, http://understandingwar.org/sites/default/files/ISIS%20Defense%20in%20Iraq%20and%20Syria%20–%20Standard.pdf (accessed July 9, 2015).  

  9. 22 U.S. Code 2656 f(d)(2). See, U.S. Department of State, Bureau of Counterterrorism, “Glossary,” http://www.state.gov/j/ct/info/c16718.htm (accessed July 8, 2015). Other official definitions of terrorism appear in various places in the U.S. Code, including 6 U.S.C. 101(16) and 18 U.S.C. 921(a)(22).  

  10. The term “democratization of violence” relates to the “increased and growing access to lethal capabilities contributing to persistent instability and the rising power of non-state actors. The increased access to a range of small arms, crew served weapons, and indirect fire weapons, and improvised explosive device developments are augmented by the inexpensive, off-the-shelf, innovative technologies being applied by terrorists, rebels, insurgents, protestors and a range of non-state actors such as e.g. small-to-medium size unmanned vehicles/drones, robotics.” See Derek Harvey, “What Is the Democratization of Violence?” October 5, 2014,
    http://derekharvey.org/2014/10/05/what-is-the-democratization-of-violence/ (accessed July 9, 2015).  

  11. See Ashton B. Carter, John Deutch, and Philip Zelikow, “Catastrophic Terrorism: Tackling the New Danger,” Foreign Affairs, Vol. 77, No. 6 (November/December 1998), https://www.foreignaffairs.com/articles/united-states/1998-11-01/catastrophic-terrorism-tackling-new-danger (accessed July 9, 2015); United States Commission on National Security /21st Century, New World Coming: American Security in the 21st Century, Supporting Research and Analysis (Washington: U.S. Government Printing Office, September 15, 1999),
    http://govinfo.library.unt.edu/nssg/NWR_A.pdf (accessed July 9, 2015).  

  12. James R. Clapper, Director of National Intelligence, “Statement for the Record: Worldwide Threat Assessment of the US Intelligence Community, Senate Armed Services Committee,” February 26, 2015, pp. 13–16,
    http://www.dni.gov/files/documents/Unclassified_2015_ATA_SFR_-_SASC_FINAL.pdf (accessed July 8, 2015).  

  13. Rohan Gunaratna, “The Global Terrorist Threat: Set to Grow in 2014,” S. Rajaratnam School of International Studies, RSIS Commentaries, January 3, 2014, https://www.rsis.edu.sg/wp-content/uploads/2014/07/CO14002.pdf (accessed July 9, 2015).  

  14. David Inserra and James Phillips, “67 Islamist Terrorist Plots Since 9/11: Spike in Plots Inspired by Terrorist Groups, Unrest in Middle East,” Heritage Foundation Issue Brief No. 4392, April 22, 2015, http://www.heritage.org/research/reports/2015/04/67-islamist-terrorist-plots-since-911-spike-in-plots-inspired-by-terrorist-groups-unrest-in-middle-east  

  15. The National Consortium for the Study of Terrorism and Responses to Terrorism (START) describes itself as “a Center of Excellence of the U.S. Department of Homeland Security.” It is hosted by the University of Maryland, College Park, Maryland. See START, website, last updated
    June 2015, http://www.start.umd.edu/gtd/ (accessed July 9, 2015).  

  16. U.S. Department of State, Bureau of Counterterrorism, “Statistical Information on Terrorism in 2013,”
    http://www.state.gov/j/ct/rls/crt/2013/224831.htm (accessed July 8, 2015).  

  17. Carol Morello, “Iraq Issues and Syria’s Civil War Cause Spike in Terror, Report Says,” The Washington Post, June 20, 2015, p. A2. 

  18. U.S. Department of State, Bureau of Counterterrorism, Country Reports on Terrorism 2014, June 2015, http://www.state.gov/j/ct/rls/crt/2014/239416.htm (accessed July 8, 2015).  

  19. Daniel L. Byman, “The Resurgence of al Qaeda in Iraq,” testimony in joint hearing, Subcommittee on Terrorism, Nonproliferation, and Trade and Subcommittee on Middle East and North Africa, Committee on Foreign Affairs, U.S. House of Representatives, December 12, 2013,
    http://www.brookings.edu/research/testimony/2013/12/12-resurgence-al-qaeda-iraq-byman (accessed July 8, 2015); Seth G. Jones, A Persistent Threat: The Evolution of al Qa’ida and Other Salafi Jihadists (Santa Monica, CA: RAND Corporation, 2014).  

  20. Ellen Knickmeyer and Hakim Almasmari, “Al Qaeda Poses New Threat in Yemen,” The Wall Street Journal, May 8, 2014, p. A11.  

  21. Bruce Hoffman, “Al Qaeda’s Uncertain Future,” Studies in Conflict & Terrorism, Vol. 36, Issue 8 (2013), pp. 635–653; Azeem Ibrahim, The Resurgence of Al-Qaeda in Syria and Iraq (Carlisle, PA: U.S. Army War College, Strategic Studies Institute, May 2014); Mary Habeck, “Getting It Right, US National Security Policy and Al Qaeda Since 2011,” American Enterprise Institute Critical Threats Project Report, April 2014.  

  22. William Braniff, testimony in hearing, State of Al Qaeda, Its Affiliates, and Associated Groups: View from Outside Experts, Committee on Armed Services, U.S. House of Representatives, February 4, 2014, http://armedservices.house.gov/index.cfm/hearings-display?ContentRecord_id=F754C1E6-F88A-4C17-92CC-D51B071AEA03 (accessed July 8, 2015).  

  23. Haim Malka and William Lawrence, “Jihadi-Salifism’s Next Generation,” Center for Strategic and International Studies, Middle East Program Analysis Paper, October 2013, http://csis.org/publication/jihadi-salafisms-next-generation (accessed July 8, 2015); Seth G. Jones, “Back to the Future: The Resurgence of Salafi-Jihadists,” testimony before the Committee on Armed Services, U.S. House of Representatives, February 4, 2014, http://www.rand.org/pubs/testimonies/CT405.html (accessed July 8, 2015).  

  24. Report, Boko Haram: Growing Threat to the U.S. Homeland, prepared by the Majority Staff of the Committee on Homeland Security, U.S. House of Representatives, September 13, 2013,
    http://homeland.house.gov/sites/homeland.house.gov/files/documents/09-13-13-Boko-Haram-Report.pdf (accessed July 8, 2015.  

  25. Thomas Joscelyn, “Boko Haram Pledges Allegiance to the Islamic State,” The Long War Journal, March 8, 2015,
    http://www.longwarjournal.org/archives/2015/03/boko-haram-leader-pledges-allegiance-to-the-islamic-state.php (accessed July 8, 2015).  

  26. Charlotte Florance, “Fighting Boko Haram Does Not End with Finding the Girls,” The Daily Signal, May 28, 2014,
    http://dailysignal.com/2014/05/28/fighting-boko-haram-end-finding-girls/ (accessed July 8, 2015); International Crisis Group, “Curbing Violence in Nigeria (II): The Boko Haram Insurgency,” Africa Report No. 216, April 3, 2014,
    http://www.crisisgroup.org/en/regions/africa/west-africa/nigeria/216-curbing-violence-in-nigeria-ii-the-boko-haram-insurgency.aspx (accessed July 8, 2015).  

  27. See, for example, General Charles C. Krulak, USMC, “The Three Block War: Fighting in Urban Areas,” Vital Speeches of the Day, Vol. 64, Issue 5 (December 15, 1997), pp. 139–142.  

  28. William J. Nemeth, Future War and Chechnya: A Case for Hybrid Warfare, unpublished master’s thesis, Naval Postgraduate School, Monterey, California, June 2002; James N. Mattis and Frank G. Hoffman, “Future Warfare: The Rise of Hybrid Wars,” U.S. Naval Institute Proceedings, Vol. 132, No. 11 (November 2005), http://milnewstbay.pbworks.com/f/MattisFourBlockWarUSNINov2005.pdf (accessed July 14, 2015); Frank G. Hoffman, “Hybrid Threats: Reconceptualizing the Evolving Character of Modern Conflict,” National Defense University, Institute for National Strategic Studies Strategic Forum No. 240, April 2009, http://www.isn.ethz.ch/Digital-Library/Publications/Detail/?lang=en&id=98862 (accessed July 14, 2015).  

  29. Stephen Biddle and Jeffrey A. Friedman, The 2006 Lebanon Campaign and the Future of Warfare: Implications for Army and Defense Policy, U.S. Army War College, Strategic Studies Institute, September 2008, http://indianstrategicknowledgeonline.com/web/THE%202006%20LEBANON%20CAMPAIGN.pdf (accessed July 14, 2015); David E. Johnson, “Military Capabilities for Hybrid War: Insights from the Israel Defense Forces in Lebanon and Gaza,” RAND Corporation Occasional Paper, 2010,
    http://www.rand.org/content/dam/rand/pubs/occasional_papers/2010/RAND_OP285.pdf (accessed July 14, 2015).  

  30. Robert M. Gates, “The National Defense Strategy: Striking the Right Balance,” Joint Force Quarterly, Issue 52 (1st Quarter 2009), p. 2–7,
    http://ndupress.ndu.edu/portals/68/Documents/jfq/jfq-52.pdf (accessed July 14, 2015); Leon E. Panetta, Remarks at the Woodrow Wilson Center, Washington, D.C., October 11, 2011, http://www.defense.gov/transcripts/transcript.aspx?transcriptid=4903 (accessed July 8, 2015).  

  31. General James T. Conway, USMC, Admiral Gary Roughead, USN, and Admiral Thad W. Allen, USCG, A Cooperative Strategy for 21st Century Seapower, October 2007, http://ise.gov/sites/default/files/Maritime_Strategy.pdf (accessed July 14, 2015); Admiral Gary Roughead, USN, Remarks at the Current Strategy Forum, Naval War College, Newport, Rhode Island, June 16, 2009; U.S. Marine Corps, Marine Corps Vision and Strategy 2025, June 2008, http://www.onr.navy.mil/~/media/Files/About-ONR/usmc_vision_strategy_2025_0809.ashx (accessed July 14, 2015); Admiral J. C. Harvey, Commander, U.S. Fleet Forces, remarks as written, Surface Navy Symposium, January 12, 2010, http://www.public.navy.mil/usff/…/hybrid_warfare-sna_speech.doc (accessed July 8, 2015); General George C. Casey, U.S. Army, “America’s Army in an Era of Persistent Conflict,” Army Magazine, Vol. 58, No. 10 (October 2008), pp. 19–28, http://www.ausa.org/publications/armymagazine/archive/2008/10/Documents/Casey_1008.pdf (accessed July 14, 2015); General Martin Dempsey, U.S. Army, “Versatility as Institutional Imperative,” Small Wars Journal, blog post, March 10, 2009, http://smallwarsjournal.com/blog/versatility-as-institutional-imperative (accessed July 14, 2015); General James F. Amos, USMC, Commandant’s Planning Guidance, 2010,
    http://www.marines.mil/Portals/59/Publications/35th%20CMC’s%20Planning%20Guidance.pdf (accessed July 14, 2015); Raymond T. Odierno, “The U.S. Army in a Time of Transition: Building a Flexible Force,” Foreign Affairs, Vol. 91, No. 3 (May/June 2012), p. 10.  

  32. National Intelligence Council, Global Trends 2030: Alternative Worlds, December 2012, p. 67, http://www.dni.gov/files/documents/GlobalTrends_2030.pdf (accessed July 14, 2015).  

  33. General Sir Richard Dannatt, Keynote Speech, Royal United Services Institute Land Warfare Conference, June 23–25, 2009,
    https://www.rusi.org/events/ref:E496B737B57852/info:public/infoID:E4A40D3C888784/#.VZA_BLtRHcs (accessed July 8, 2015); General Lord David Richards, “Reflections on 10 Years of Regional Security Changes,” International Institute for Strategic Studies, IISS Manama Dialogue 2014: 10th Regional Security Summit, December 7, 2014, https://www.iiss.org/en/events/manama%20dialogue/archive/manama-dialogue-2014-3b96/plenary5-845a/richards-f42b (accessed July 14, 2015). See also “Hybrid Insecurity in Developing Countries,” Chapter 2, Part III in International Institute for Strategic Studies, Strategic Survey 2014: The Annual Review of World Affairs (London: Routledge, 2014, pp. 53–64; “Hybrid Warfare: Challenge and Response,” Chapter 1, Part III in International Institute for Strategic Studies, The Military Balance 2015: The Annual Assessment of Global Military Capabilities and Defence Economics (London: Routledge, 2015), pp. 17–20.  

  34. Frank G. Hoffman, Conflict in the 21st Century: The Rise of Hybrid Wars (Arlington, VA: Potomac Institute for Policy Studies, December 2007, pp. 14, 58, http://www.potomacinstitute.org/images/stories/publications/potomac_hybridwar_0108.pdf (accessed July 14, 2015); Frank G. Hoffman, “Hybrid vs. Compound War,” Armed Forces Journal, October 2009, http://indianstrategicknowledgeonline.com/web/4198658.pdf (accessed July 14, 2015).  

  35. Anders Fogh Rasmussen, quoted in Mark Landler and Michael Gordon, “NATO Chief Warns of Duplicity by Putin on Ukraine,” The New York Times, July 8, 2014, http://www.nytimes.com/2014/07/09/world/europe/nato-chief-warns-of-duplicity-by-putin-on-ukraine.html?_r=0 (accessed July 8, 2015).  

  36. Sam Jones, “Ukraine: Russia’s New Art of War,” Financial Times, August 28, 2014, http://www.ft.com/cms/s/2/ea5e82fa-2e0c-11e4-b760-00144feabdc0.html#ixzz3O01r9qjy (accessed July 14, 2015); Yuri Drazdow “Modern Hybrid War, by Russia’s Rules,” Minsk Herald,
    November 3, 2014, http://minskherald.com/2014/11/russian-new-military-doctrine/ (accessed July 8, 2015).  

  37. Robert Strausz-Hupé, William R. Kintner, James E. Dougherty, and Alvin J. Cottrell, Protracted Conflict (New York: Harper & Row for the Foreign Policy Research Institute, 1959). For modern commentators, see Peter Pomerantsev, “How Putin Is Reinventing Warfare,” Foreign Policy, May 5, 2014, http://foreignpolicy.com/2014/05/05/how-putin-is-reinventing-warfare/ (accessed July 15, 2015); S. G. Chekinov and S. A. Bogdanov, “The Nature and Content of a New-Generation Warfare,” Military Thought, Issue 4 (2013), pp. 12–23,
    http://www.eastviewpress.com/Files/MT_FROM%20THE%20CURRENT%20ISSUE_No.4_2013.pdf (accessed July 8, 2015).  

  38. General Valeriy Gerasimov, “Nonlinear Warfare,” VPK, February 2013; Janis Berzins, “Russia’s New Generation Warfare in Ukraine: Implications for Latvian Defense Policy,” National Defence Academy of Latvia, Center for Security and Strategic Research Policy Paper No. 2, April 2014.  

  39. Rasmussen, quoted in Landler and Gordon, “NATO Chief Warns of Duplicity by Putin on Ukraine.”  

  40. Marc Lindemann, “Laboratory of Asymmetry: The 2006 Lebanon War and the Evolution of Iranian Ground Tactics,” Military Review, May–June 2010, pp. 105–116, http://usacac.army.mil/CAC2/MilitaryReview/Archives/English/MilitaryReview_20100630_art015.pdf (accessed July 8, 2015).  

  41. F. G. Hoffman, “‘Hybrid Threats’: Neither Omnipotent nor Unbeatable,” Orbis, Vol. 54, Issue 3 (Summer 2010), pp. 441–455.  

  42. Robert A. Newson, “The 3 Areas Where the Navy Is Adjusting Its Operating Strategy,” Defense One, May 13, 2015,
    http://www.defenseone.com/ideas/2015/05/3-areas-where-navy-adjusting-its-operating-strategy/112750/ (accessed July 8, 2015).  

  43. For more on this topic, see Frank Hoffman, “On Not-So-New Warfare: Political Warfare vs Hybrid Threats,” War on the Rocks, July 28, 2014, hhttp://warontherocks.com/2014/07/on-not-so-new-warfare-political-warfare-vs-hybrid-threats/ (accessed July 17, 2015), and David Maxwell, “Do We Really Understand Unconventional Warfare?” Small Wars Journal, October 23, 2014,
    http://smallwarsjournal.com/jrnl/art/do-we-really-understand-unconventional-warfare (accessed July 17, 2015).  

  44. For Kennan’s policy memo promoting this initiative under the auspices of the State Department, see “Policy Staff Planning Memorandum,” May 4, 1948, http://academic.brooklyn.cuny.edu/history/johnson/65ciafounding3.htm (accessed July 15, 2015).  

  45. U.S Army Special Operations Command, “SOF Support to Political Warfare,” White Paper, March 10, 2015,
    https://dl.dropboxusercontent.com/u/6891151/Support%20to%20Political%20Warfare%20White%20Paper%20v2.3-RMT%20%2810MAR2015%29%20%20%20.pdf (accessed July 15, 2015).  

  46. U.S. Army Special Operations Command, “Counter-Unconventional Warfare,” White Paper, September 26, 2014,
    https://info.publicintelligence.net/USASOC-CounterUnconventionalWarfare.pdf (accessed July 15, 2015).  

  47. David Maxwell, “Taking a Spoon to a Gunfight,” War on the Rocks, April 2, 2014, http://warontherocks.com/2014/04/taking-a-spoon-to-a-gunfight/ (accessed July 15, 2015). See also Steven Metz, “In Ukraine, Russia Reveals Its Mastery of Unrestricted Warfare,” World Politics Review, April 16, 2014, http://www.worldpoliticsreview.com/articles/13708/in-ukraine-russia-reveals-its-mastery-of-unrestricted-warfare (accessed July 15, 2015).  

  48. James Jay Carafano, Wiki at War: Conflict in a Socially Networked World (College Station: Texas A&M University Press, 2012).  

  49. Jolanta Darczewska, “The Anatomy of Russian Information Warfare: The Crimean Operation, A Case Study,” Centre for Eastern Studies Point of View No. 42, May 2014, http://www.osw.waw.pl/sites/default/files/the_anatomy_of_russian_information_warfare.pdf (accessed July 15, 2015).  

  50. Lawrence Freedman, “Ukraine and the Art of Limited Conflict,” Survival: Global Politics and Strategy, Vol. 56, Issue 6 (December 2014–January 2015), pp. 7–38, https://www.iiss.org/en/publications/survival/sections/2014-4667/survival–global-politics-and-strategy-december-2014-january-2015-bf83/56-6-02-freedman-6983 (accessed July 15, 2015).  

  51. Dean Cheng, “America Needs a Comprehensive Strategy for Countering China’s Expanding Perimeter of National Interests,” Heritage Foundation Issue Brief No. 4397, April 28, 2015, http://www.heritage.org/research/reports/2015/04/america-needs-a-comprehensive-strategy-for-countering-chinas-expanding-perimeter-of-national-interests.  

  52. Christopher Layne, “Sleepwalking with Beijing,” The National Interest, No. 137 (May/June 2015), p. 45.  

  53. Graham T. Alison, statement in hearing, China, the U.S., and the Asia–Pacific, Committee on Armed Services, U.S. Senate, April 14, 2015,
    http://www.armed-services.senate.gov/imo/media/doc/Allison_04-14-15.pdf (accessed July 8, 2015).  

  54. Adam P. Liff and G. John Ikenberry, “Racing Toward Tragedy? China’s Rise, Military Competition in the Asia Pacific, and the Security Dilemma,” International Security, Vol. 39, No. 2 (Fall 2014), p. 53, http://www.mitpressjournals.org/doi/pdf/10.1162/ISEC_a_00176
    (accessed July 15, 2015).  

  55. James Jay Carafano, “Avoiding the Unthinkable: Preventing a US–China Nuclear War,” The National Interest, February 9, 2015,
    http://nationalinterest.org/feature/avoiding-the-unthinkable-preventing-us-china-nuclear-war-12209?page=2 (accessed July 8, 2015).  

  56. Joshua Keating, “Russia Gets Religion,” Slate, November 11, 2014, http://www.slate.com/articles/news_and_politics/foreigners/2014/11/russia_orthodox_church_will_vladimir_putin_eradicate_all_boundaries_between.html (accessed July 8, 2015).  

  57. Chuck Hagel, “The Defense Innovation Initiative,” memorandum, U.S. Department of Defense, November 15, 2014,
    http://www.defense.gov/pubs/OSD013411-14.pdf (accessed July 15, 2015); “Who’s Afraid of America?” The Economist, June 13, 2015,
    (accessed July 8, 2015).  

  58. See Daniel Gouré, “Building the Right Military for a New Era: The Need for an Enduring Analytic Framework,” in Dakota L. Wood, ed., 2015 Index of U.S. Military Strength: Assessing America’s Ability to Provide for the Common Defense (Washington, DC: The Heritage Foundation, 2015), pp. 27–36, http://ims-2015.s3.amazonaws.com/2015_Index_of_US_Military_Strength_FINAL.pdf (accessed July 29, 2015).  

  59. Dov S. Zakheim, “Restoring American Supremacy,” The National Interest, No. 136 (March/April 2015),
    http://www.nationalinterest.org/feature/restoring-american-supremacy-12325 (accessed July 8, 2015).  

  60. Nadia Schadlow, “The Problem with Hybrid Warfare,” War on the Rocks, April 2, 2015, http://warontherocks.com/2015/04/the-problem-with-hybrid-warfare/ (accessed July 8, 2015).  

  61. Ashton Carter, “Press Availability with Secretary Carter at NATO Headquarters, Brussels, Belgium,” June 25, 2015, http://www.defense.gov/Transcripts/Transcript.aspxTranscriptID=5645 (accessed July 8, 2015).  

  62. The House Armed Services Committee is leaning forward in this area. See Tim Starks, “New House Armed Services Chairman Plans Focus on Unconventional Warfare,” Roll Call, January 14, 2015, http://blogs.rollcall.com/five-by-five/new-house-armed-services-chairman-plans-focus-on-unconventional-warfare/?dcz= (accessed July 8, 2015).  

  63. Introduction, Report of the Independent QDR, The QDR in Perspective: Meeting America’s National Security Needs in the 21st Century, Final Report of the Quadrennial Defense Review Independent Panel, United States Institute for Peace, 2010,
    http://www.usip.org/sites/default/files/qdr/IntroCompilation.pdf (accessed July 8, 2015).