America’s Counterterrorism Gamble
U.S. national security is shifting from a focus on countering terrorist groups to competing with state adversaries. While it is reasonable to focus more attention on adversaries like Russia, Iran, North Korea, and China, terrorist groups like the Islamic State, al-Qaeda, and Hezbollah still present a threat to the United States. Indeed, state and non-state adversaries frequently overlap, since countries like Iran use terrorist groups like Hezbollah to pursue their interests. It would be unnecessarily risky for the United States to move too quickly away from countering terrorists while the threat is still high, allowing groups and networks to resurge.
Counterterrorism has quietly taken a back seat in the hierarchy of U.S. national security interests. Some U.S. governments officials have argued that groups like the Islamic State have been “crushed” and “eradicated.”1 In addition, U.S. strategy documents have outlined a shift from counterterrorism against non-state actors like al-Qaeda and the Islamic State to competition with states like China, Russia, Iran, and North Korea. As the unclassified version of the National Defense Strategy notes, “Inter-state strategic competition, not terrorism, is now the primary concern in U.S. national security.”2 This shift has been cheered by some academics and pundits who have argued that the threat from terrorism is significantly overstated. Writing in Foreign Affairs, for example, Robert Malley and Jon Finer argue that America’s excessive focus on terrorism “disfigures American politics, distorts U.S. policies, and in the long run will undermine national security.”3 John Mueller and Mark Stewart contend that the counterterrorism hysteria after 9/11 is loosely comparable to the frenzy over witches in Europe between 1480 and 1680, and has been overly “expensive, exhaustive, bewildering, chaotic, and … paranoia inducing.”4
Focusing on state adversaries is reasonable and long overdue. The United States faces challenges from an increasingly powerful China that is extending its global economic, political, and military reach; a revanchist Russia that is trying to reassert itself after losing roughly half its population following the break-up of the Soviet Union and much of its global influence; an activist Iran that continues to build its missile capabilities and support proxies in countries from Syria and Lebanon to Yemen and Iraq; and a North Korea with an erratic leader that has access to nuclear weapons and ballistic missiles.
It would be imprudent if the United States were to move too quickly away from countering terrorists while the threat is still high.
While it is sensible for the United States to rebalance its resources to compete with state adversaries, the terrorism threat to the United States remains substantial at home and overseas. Neither the Islamic State nor al-Qaeda are dead. In Iraq, Abu Bakr al-Baghdadi’s organization is making a comeback in western and central parts of the country and orchestrating a wave of bombings, ambushes, assassinations, and kidnappings. What’s more, many of the opportunities leveraged by groups like the Islamic State and al-Qaeda—from weak or corrupt regimes in Somalia, Libya, and Afghanistan to political, social, or economic grievances in Iraq and Syria—have not been adequately addressed. This means that the United States should carefully walk a tightrope. U.S. policymakers need to continue using special operations, intelligence, diplomatic, development, and law enforcement tools to aggressively target the Islamic State, al-Qaeda, and other extremists that they inspire at home and overseas. At the same time, the United States also needs to compete with state adversaries to protect U.S. interests. Both sets of challenges are important.
The temptation now is to prioritize one over the other and to begin withdrawing U.S. forces and capabilities from key counterterrorism missions. This would be a serious mistake. The reality is that the threat from state and non-state adversaries overlap, since states like Iran and Russia use non-state proxies to pursue their interests. It would be imprudent and perhaps dangerous if the United States were to move too quickly away from countering terrorists while the threat is still high, allowing these groups to resurge.
Terrorism Is Still a Threat
There is substantial evidence that the terrorism threat is still serious.
Global Terrorism: Terrorist activity is high across the world. As Figure 1 highlights, the number of deaths from terrorism has come down slightly from peak levels in 2014. But it is still at one of the highest points since 2000. There is a similar trend with the number of terrorism incidents, which remain at near-peak levels. Most of the deaths from terrorism are occurring in countries like Iraq and Afghanistan. But these attacks are perpetrated by groups like the Islamic State, al-Qaeda, and the Taliban, which also target the U.S. homeland or its forces overseas.
There are at least 66 Salafi-jihadist groups in 2018—the same number as 2016, the highest recorded year in the past four decades.
Figure 1: Deaths from Terrorism by Region5
Islamic Extremists: The threat from Salafi-jihadist groups like al-Qaeda and the Islamic State also remains serious.6 The number of Salafi-jihadist groups today is at the highest recorded level since 1980, according to CSIS estimates. There are at least 66 Salafi-jihadist groups today—the same number as 2016, the highest recorded year in the past four decades. To put this into perspective, there are nearly three times as many Salafi-jihadist groups today than in 2001, when the 9/11 attacks occurred. What’s more, there are as many as 230,000 Salafi-jihadist and allied fighters worldwide in 2018, according to CSIS estimates, which is among the highest totals since 1980.7 In addition, there are roughly 1,000 foreign fighters from 50 countries that supported the Islamic State and other groups, which are currently held by the Kurdish-led Syrian Democratic Forces in facilities like Ainissa in Syria.8 Some of these fighters have already been released; others will likely be released in the future. A growing number of their home nations don’t want to bring them back for prosecution.
The regions with the highest number of groups and fighters include the Middle East, North Africa, and South Asia, with particularly high numbers in Syria, Iraq, Libya, Pakistan, and Afghanistan. These trends suggest that the United States and other countries will continue to face a large, fluid pool of Salafi-jihadists for the foreseeable future. Of course, not all these groups are plotting attacks against the United States or its interests overseas. But the large pool of Salafi-jihadists is still concerning.
Despite the Islamic State’s loss of territory, the group boasts as many as 26,000 fighters across multiple continents, with particularly large numbers in Iraq, Syria, and Nigeria.
Despite the Islamic State’s loss of territory, the group boasts as many as 26,000 fighters across multiple continents, with particularly large numbers in Iraq, Syria, and Nigeria.9 Even with its decline in territorial control, Islamic State leaders have shifted from governing territory to conducting guerrilla warfare; developing a long-term educational and ideological campaign; and engaging in propaganda, fund-raising, recruitment, and communication on social media and other forums.10 Islamic leaders continue to criticize the West as corrupt and immoral. As one article in the Islamic State publication Dabiq explained, “We hate you because your secular, liberal societies permit the very things that Allah has prohibited while banning many of the things He has permitted.” It continued that “your secular liberalism has led you to tolerate and even support ‘gay rights,’ to allow alcohol, drugs, fornication, gambling, and usury to become widespread, and to encourage the people to mock those who denounce these filthy sins and vices.”11
In Iraq, the Islamic State has re-established its clandestine intelligence network in parts of provinces like Anbar, Diyala, Kirkuk, and Salahuddin, as well as conducted a growing number of attacks against government officials, tribal elders, village chiefs, and targets like oil pipelines and electricity infrastructure.12 The Islamic State Khorasan Province has conducted a number of attacks in both Afghanistan and Pakistan, including a July 2018 strike in the Pakistan province of Balochistan that killed at least 159 people.13
Al-Qaeda also includes as many as 34,000 fighters, particularly in such countries as Syria, Somalia, and Yemen.14 Al-Qaeda figures, led by leader Ayman al-Zawahiri, have focused on joining local insurgencies rather than trying to usurp them. In some cases, as with the Afghan Taliban, al-Qaeda leaders have pledged bay’ah (or loyalty) to local groups. In addition, al-Qaeda has focused its energy and resources on fighting local governments like the Assad regime, rather than Western governments like the United States for now. But al-Qaeda leaders consider the United States the main enemy and still desire to conduct external operations against the United States and other Western countries. As al-Zawahiri has acknowledged: “The military work firstly targets the head of (international) disbelief, America and its ally Israel, and secondly its local allies that rule our countries.”15 Figure 2 highlights the global activity of the Islamic State and al-Qaeda, along with their main affiliates.
Al-Qaeda includes as many as 34,000 fighters, particularly in such countries as Syria, Somalia, and Yemen.
Figure 2: Al-Qaeda and Islamic State Violent Activity, 2016-201816
Threat to the United States: The terrorism threat to Americans is likely higher overseas in such areas as North and East Africa, the Middle East, parts of Asia, and even Europe than it is in the U.S. homeland. But there is still a concern of attacks in the United States from individuals inspired by extremist ideologies. The FBI has active investigations of Islamic State-inspired terrorist cases in every state in the United States. Over 162 individuals have been charged in the United States with offenses related to the Islamic State since March 2014.17 The number of arrests has been highest in states like California, Arizona, Minnesota, Texas, New York, and Florida. Since 2011, over 200 Americans have traveled to Syria and Iraq to participate in the conflicts, many of whom have not returned to the United States. A few Americans, like Ibraheem Musaibli from Dearborn, Michigan, have been—or will be—prosecuted in the United States.18 The vast majority of those arrested have been U.S. citizens or permanent residents, not refugees or asylum seekers.19 One of the most recent terrorist plots was led by Demetrius Nathaniel Pitts, a U.S. citizen, who was charged with attempting to provide material support to al-Qaeda. He was arrested after plotting a July 4, 2018 attack in Cleveland and scouting locations to kill scores of civilians. As Pitts remarked, “I’m trying to figure out something that would shake [Americans] up on the 4th of July… What would hit them at their core? Blow up in the [sic], have a bomb blow up in the 4th of July parade.”20
More Americans believe that terrorism should be a priority (73 percent) than other issues, such as education, the economy, and health care costs.
Americans also continue to consider terrorism a significant concern. More Americans view terrorism as a priority for the United States (73 percent) than other policy priorities, such as education (72 percent), the economy (71 percent), and health care costs (68 percent)—according to a Pew Research Center poll highlighted in Figure 3.21 Some skeptics consider these public sentiments irrational or uninformed.22 As one assessment concluded, Americans may well have “an exaggerated sense of the threat or misunderstand it, and their political leaders might manipulate or exploit their concerns.” Hyping the terrorism, the authors conclude, “has become a national—and bipartisan—tradition.”23 Yet this dismissive view ignores the reality that state adversaries like China, Russia, and even Iran are unlikely to conduct physical attacks against America, at least for the foreseeable future. Their cyber, information warfare, and other capabilities certainly present a threat, as U.S. intelligence officials have warned.24 And a war with China, Russia, North Korea, or Iran—however unlikely—would be devastating. But terrorists like al-Qaeda and the Islamic State have the capability and the intention to conduct attacks against civilian targets. And U.S. citizens expect their government to protect them. Americans might reasonably ask what is more likely: an attack against a U.S. target at home or overseas by a terrorist, or an attack by China, Russia, Iran, or other states. Americans believe—not without reason—that terrorism remains the more significant threat for now.
Figure 3: U.S. Public Priorities, 201825
It should come as little surprise, then, that the U.S. military is conducting counterterrorism activities in 76 countries overseas. But only a minority of these activities are combat missions. The majority are efforts to build the capacity of partner nations. U.S. military activity includes one or more of the following in those 76 countries: conducting air and drone strikes (7 countries); deploying combat troops (15 countries); constructing or retaining military bases (44 countries); and building the capacity of partners to conduct counterterrorism and other actions (58 countries).26
Threat to Europe: The terrorism threat to America’s allies in Europe is also nearly at an all-time high. Take the United Kingdom. There were five successful attacks in 2017 in the UK. Four of the attacks were perpetrated by Islamic extremists, the most in UK history from Islamic extremism.27 On March 22, British-born Khalid Masood, a convert to Islam, drove a sports utility vehicle into pedestrians crossing Westminster Bridge in London, killing three people. Masood then took two carving knives out of his vehicle and stabbed police officer Keith Palmer, killing him outside of Parliament. On May 22, British-born Salman Abedi, who had contact with Islamic State-affiliated individuals in Libya, detonated an improvised explosive device in the foyer of Manchester Arena following a concert by the American pop singer Ariana Grande. The attack killed 22 people, and 10 of the victims were under 20 years old. On June 3, three men—Khuram Butt (British), Rachid Redouane (Moroccan), and Youssef Zaghba (Italian and Moroccan)—drove a van into London Bridge, killing two people. They then jumped out of the van and killed six more people using large knives. Butt had direct links with the UK terrorist group Al-Muhajiroun. On September 15, 2017, an 18-year old Iraqi asylum seeker named Ahmed Hassan detonated a bomb using triacetone triperoxide (TATP) on a District line train at Parsons Green Underground station in London. Thirty people were treated for burn and other injuries.28
In addition, there has been an increase in the number of failed, foiled, and completed attacks in the UK, as highlighted in Figure 4.29 There were also more terrorist-related arrests in the UK in 2017 than in any previous year since 2001. Between December 2013 and May 2018, British intelligence and law enforcement agencies thwarted 25 plots from extreme Islamic groups.31 Most of these plots were inspired by the Islamic State and its ideology, rather than directed by Islamic State operatives. Based on the attacks and plots, the UK’s Joint Terrorism Analysis Centre has kept the threat level high in the UK.32 Large numbers of individuals in the UK remain under investigation or have previously been the subject of a terrorism investigation. By the end of 2017, MI5 and the police had over 500 ongoing terrorism investigations involving more than 3,000 subjects of interest, along with a growing pool of more than 20,000 individuals who had previously been the subject of terrorist investigations.33
Figure 4: Arrests and Proceedings for UK Terrorist-Related Offenses, 2010-201734
More broadly, the terrorism threat in Europe is high. The European Union Agency for Law Enforcement Cooperation concluded in 2018 that “there has been an increase in the frequency of jihadist attacks” in Europe, which “cause more deaths and casualties than any other terrorist attacks.”35 Most of these attacks were perpetrated by homegrown terrorists, who were radicalized in their home European countries and did not have direct links to the Islamic State, al-Qaeda, or other groups. The tactics of terrorists varied considerably and included vehicles used to kill pedestrians, rudimentary improvised explosive devices, knives, swords, small arms, and blunt objects like hammers.36
Competition between the United States and its main state adversaries will likely be irregular—not conventional.
As America shifts its national security priorities from terrorism to state adversaries, there is a potentially ironic twist. The United States remains the world’s preponderant military power. For Russia, Iran, North Korea, and even China, conventional or nuclear war with the United States would be risky and prohibitively costly. What’s more, America’s struggles in Afghanistan and Iraq suggest that the U.S. military is vulnerable when faced with state and non-state actors like the Taliban that resort to irregular strategies, operations, and tactics.
These realities suggest that competition between the United States and its main adversaries will likely be irregular—not conventional. Russia will likely focus on a suite of overt and covert actions, from supporting proxies in Syria, Ukraine, and the Baltics to information warfare. Iran will attempt to expand its power through proxies in Lebanon, Syria, Iraq, Yemen, Afghanistan, and Bahrain—not by amassing a more potent army, navy, or air force capable of fighting conventional battles against the United States. China is already spreading its influence in the Pacific by utilizing economic coercion, conducting a sophisticated information campaign, and resorting to fishing vessels and other “grey zone” tactics to lay claim to islands. Even North Korea will likely continue to develop its special operations and cyber capabilities.
Take Iran, which possesses formidable irregular capabilities led by the Islamic Revolutionary Guards Corps-Quds Force (IRGC-QF). Tehran has adopted a strategy of “forward defense,” which involves supporting sub-state proxies across the Middle East and beyond.37 Over the past several decades, the Islamic Republic has used groups like Lebanese Hezbollah to influence local politics to Tehran’s advantage, employed religious ideology to recruit and inspire militants, utilized economic influence as a means of political leverage, engaged in psychological warfare to promote the Islamic revolution’s ideology through its national broadcasting network, engaged in cultural and religious diplomacy efforts, and co-opted grassroots movements. Iran’s proxies play a prominent role in Tehran’s irregular warfare strategy and, like Hezbollah, conduct terrorist attacks. Of particular interest is the IRGC-QF’s external operations department—Department 400 (also known as the Misaq Unit)—and its regional offices for covert action that cover such countries as Iraq, Yemen, Bahrain, Iraq, Saudi Arabia, Pakistan, and Afghanistan. Iran has also encouraged some of these groups to establish political organizations, with Hezbollah serving as the most successful example.38
A Persistent Threat
The United States—like other Western countries—will likely continue to face threats from non-state actors like the Islamic State and al-Qaeda, as well as states like Iran, Russia, and China. These threats often overlap. As Andrew Parker, the head of MI5, the UK’s domestic intelligence agency, acknowledged in 2018: “In parallel to this state-level hostile activity, Europe faces an intense, unrelenting and multidimensional international terrorist threat. Daesh continues to pose the most acute threat, but al-Qaeda and other Islamist terrorist groups haven’t gone away.”39 Parker also added a reminder that governments will not be able to stop every attack: “I’ve always been clear that we can’t hope to stop everything. But I can tell you that MI5 and our partner agencies are bringing the full weight of our growing capabilities to counter this new intensity of threat. Day in and day out we are identifying and disrupting threats: stopping terrorism. Our response is unrelenting.”40 Parker’s comments highlight the need to remain vigilant and resilient, while keeping terrorism threats in perspective.
Developing national security is more an art than a science, especially trying to prioritize among a range of important issues. A high school student experimenting with weights on a scale finds that taking off mass from one side too quickly—or adding too much mass to the other side—will cause the scale to lose its balance. Indeed, balancing U.S. national security priorities in today’s world needs to happen gradually. The challenge is not that U.S. officials are devoting attention to deal with state adversaries like Russia, China, Iran, and North Korea. These countries present legitimate threats to the United States at home and abroad.
Rather, the mistake would be declaring victory too quickly against terrorism—and then shifting too many resources and too much attention away when the threat remains significant. The United States has established an effective and fairly efficient counterterrorism architecture, with organizations like the National Counterterrorism Center and Joint Special Operations Command, which should continue to aggressively pressure terrorists. Some U.S. officials have already supported pulling U.S. counterterrorism forces out of areas like Syria and northern Africa, despite the persistence of groups like al-Qaeda and the Islamic State there.41 A significant withdrawal of U.S. special operations forces, intelligence operatives, intelligence resources, and development and diplomatic experts for counterterrorism in key areas of Africa, the Middle East, and South Asia would be unnecessarily risky.
Finding a balance is the most important challenge.
Seth G. Jones holds the Harold Brown Chair, is director of the Transnational Threats Project, and is a senior adviser to the International Security Program at the Center for Strategic and International Studies in Washington, D.C. He is the author, most recently, of “A Covert Action: Reagan, the CIA, and the Cold War Struggle in Poland” (W.W. Norton).
CSIS Briefs are produced by the Center for Strategic and International Studies (CSIS), a private, tax-exempt institution focusing on international public policy issues. Its research is nonpartisan and nonproprietary. CSIS does not take specific policy positions. Accordingly, all views, positions, and conclusions expressed in this publication should be understood to be solely those of the author(s).
© 2018 by the Center for Strategic and International Studies. All rights reserved.
 On “crushed,” see, for example, National Security Strategy of the United States of America (Washington, DC: White House, December 2017): 1. On “eradicated” see President Donald J. Trump, interview with Sean Hannity, Fox News, July 17, 2018, https://www.youtube.com/watch?v=XfS2n21Cnpo.
Summary of the 2018 National Defense Strategy of the United States of America (Washington, DC: U.S. Department of Defense, January 2018), 1.
 Robert Malley and Jon Finer, “The Long Shadow of 9/11: How Counterterrorism Warps U.S. Foreign Policy,” Foreign Affairs 97, no. 4 (July / August 2018): 59.
 John Mueller and Mark G. Stewart, Chasing Ghosts: The Policing of Terrorism (New York: Oxford University Press, 2016), p. 2.
 START, Global Terrorism Database, downloaded in July 2018.
 This report defines Salafi-jihadist based on two criteria. First, the individual or group emphasizes the importance of returning to a “pure” Islam, that of the Salaf, the pious ancestors. Second, the group believes that violent jihad is fard ‘ayn (a personal religious duty).
 The number of Salafi-jihadist groups and fighters comes from the CSIS Transnational Threats Project’s Salafi-jihadist data set.
 Charlie Savage, “As ISIS Fighters Fill Prisons in Syria, Their Home Nations Look Away,” New York Times, July 19, 2018, available at: https://www.nytimes.com/2018/07/18/world/middleeast/islamic-state-detainees-syria-prisons.html.
 The information comes from the CSIS Transnational Threats Project’s Salafi-jihadist data set. CSIS estimates include a low of 12,855 fighters and high of 25,690 fighters for the Islamic State.
 On the Islamic State’s educational activity, see, for instance, reports from the interrogation of Islamic State leader Abu Zaid al-Iraqi. Joby Warrick and Souad Mekhennet, “New Clues Bolster Belief that ISIS Leaders is Still Alive—and Busy with a Chilling New Mission,” Washington Post, May 19, 2018, available at: https://www.washingtonpost.com/world/national-security/new-clues-bolster-belief-that-isis-leader-is-still-alive--and-busy-with-a-chilling-new-mission/2018/05/19/83c2a62e-5ad2-11e8-858f-12becb4d6067_story.html?noredirect=on&utm_term=.85becd840594.
 “Why We Hate You and Why We Fight You,” Dabiq 15 (1437 Shawwal): 32. Also see, for example, “The Fitrah of Mankind and the Near-Extinction of the Western Woman,” Dabiq 15 (1437 Shawwal): 20; “Foreword,” Dabiq 15 (1437 Shawwal): 4-5.
 See, for example, Liz Sly and Mustafa Salim, “ISIS Is Making a Comeback in Iraq Just Months after Baghdad Declared Victory,” Washington Post, July 17, 2018, https://www.washingtonpost.com/world/isis-is-making-a-comeback-in-iraq-less-than-a-year-after-baghdad-declared-victory/2018/07/17/9aac54a6-892c-11e8-9d59-dccc2c0cabcf_story.html?noredirect=on&utm_term=.283696e52248.
 Syed Ali Shah, “Mastung Bombing,” Dawn (Pakistan), July 13, 2018, https://www.dawn.com/news/1419812.
 The information comes from the CSIS Transnational Threats Project’s Salafi-jihadist data set. CSIS estimates include a low of 21,050 fighters and high of 34,200 fighters for al-Qaeda. Note that we included numbers from Hay’at Tahrir al-Sham, which, at the moment, is not an official affiliate of al-Qaeda. However, we assess that there is a possibility of realignment with al-Qaeda’s central leadership in the future. On al-Qaeda numbers also see Bruce Hoffman, “Al-Qaeda’s Resurrection,” Council on Foreign Relations Expert Brief, March 6, 2018, available at: https://www.cfr.org/expert-brief/al-qaedas-resurrection.
 Ayman al-Zawahiri, “General Guidelines for Jihad,” As-Sahab Media, 1434, 1.
 The CSIS Transnational Threats Project compiled data from the Armed Conflict Location and Event Data Project (ACLED) that looked at Islamic State and al-Qaeda activity. To gauge activity and operational tempo, the CSIS Transnational Threats Projects looked at the following event types pertaining to each group: battle in which there is no territorial change; battle in which the non-state actor gains territory; headquarters or base established; violence against civilians; and remote violence.
 GWU Extremism Tracker, https://extremism.gwu.edu/sites/g/files/zaxdzs2191/f/Jun2018_Update_IS%20in%20America.pdf.
 Rukmini Callimachi, Eric Schmitt, and Charlie Savage, “American Accused of Being ISIS Fighter in Syria Faces Prosecution in U.S.,” New York Times, July 19, 2018, available at: https://www.nytimes.com/2018/07/19/world/middleeast/islamic-state-us-detainee.html.
 See, for example, Brian Michael Jenkins, The Origins of America’s Jihadists (Santa Monica, CA: RAND, 2017); Lorenzo Vidino and Seamus Hughes, ISIS in America: From Retweets to Raqqa (Washington, DC: George Washington University, Program on Extremism, December 2015).
 U.S. Department of Justice, “Ohio Man Arrested for Attempting to Assist a Foreign Terrorist Organization with Homeland Attack Plot,” July 2, 2018, https://www.justice.gov/opa/pr/ohio-man-arrested-attempting-assist-foreign-terrorist-organization-homeland-attack-plot.
 Pew Research Center, Economic Issues Decline Among Public’s Policy Priorities (Washington, DC: Pew Research, January 2018): 2.
 On skeptics see, for example, John Mueller and Mark G. Stewart, “Why Are Americans Still So Afraid of Islamist Terrorism?” Washington Post, March 23, 2018, https://www.washingtonpost.com/news/monkey-cage/wp/2018/03/23/why-are-americans-still-so-afraid-of-islamic-terrorism/?noredirect=on&utm_term=.c68900af47a3; Malley and Finer, “The Long Shadow of 9/11,” 58-69.
 Malley and Finer, “The Long Shadow of 9/11,” 59-61.
 See, for example, Daniel R. Coats, Worldwide Threat Assessment of the U.S. Intelligence Community (Washington, DC: Office of the Director of National Intelligence, March 2018).
 Pew Research Center, Economic Issues Decline Among Public’s Policy Priorities, 2.
 Stephanie Savell and Maria Ji, Current United States Counterterror War Locations, January 2018, http://watson.brown.edu/costsofwar/files/cow/imce/papers/Current%20US%20Counterterror%20War%20Locations_Costs%20of%20War%20Project%20Map.pdf.
 Europol, European Union Terrorist Situation and Trend Report (The Hague: European Union Agency for Law Enforcement Cooperation, 2018): 10.
 David Anderson, “Attacks in London and Manchester: Independent Assessment of MI5 and Police Internal Reviews,” December 2017, https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/664682/Attacks_in_London_and_Manchester_Open_Report.pdf.
 European Union Agency for Law Enforcement Cooperation (Europol), European Union Terrorism Situation and Trend Report2018 (Brussels: Europol, 2018): 54.
 Grahame Allen and Noel Dempsey, Terrorism in Great Britain: The Statistics (London: House of Commons, June 7, 2018): 14.
 Andrew Parker, Director General of the Security Service, “Speech to the BfV Symposium in Berlin,” May 14, 2018, https://www.mi5.gov.uk/news/director-general-andrew-parker-speech-to-bfv-symposium.
 See, for example, Threat Level to the UK from International Terrorism Lowered to Severe (London: MI5, September 17, 2017), https://www.mi5.gov.uk/news/threat-level-to-the-uk-from-international-terrorism-lowered-to-severe-0; Threat Level to the UK from International Terrorism Raised to Critical (London: MI5, September 15, 2017), https://www.mi5.gov.uk/news/threat-level-to-the-uk-from-international-terrorism-raised-to-critical-0; Threat Level to the UK from International Terrorism Lowered to Severe (London: MI5, May 27, 2017), https://www.mi5.gov.uk/news/threat-level-to-the-uk-from-international-terrorism-lowered-to-severe.
Publication of David Anderson QC’s Report on the Terrorist Attacks of March-June 2017 (London: MI5, December 5, 2017), https://www.mi5.gov.uk/news/publication-of-david-anderson-qc%E2%80%99s-report-on-the-terrorist-attacks-of-march-june-2017.
 Data are from the National Counter-Terrorism Police Operations Centre (NCTPOC) and Crown Prosecution Service Counter-Terrorism Division, https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/685887/police-powers-terrorism-dec17-annual-tables.xlsx.
 Europol, European Union Terrorism Situation and Trend Report2018, 5.
 Europol, European Union Terrorism Situation and Trend Report2018, 5, 24.
 Vali Nasr, “Iran Among the Ruins: Tehran’s Advantage in a Turbulent Middle East,” Foreign Affairs 97, no. 2 (March/April 2018): 111.
 See, for example, Joseph Daher, Hezbollah: The Political Economy of Lebanon’s Party of God (New York: Pluto Press, 2016); Matthew Levitt, Hezbollah: The Global Footprint of Lebanon's Party of God, revised edition (Washington, DC: Georgetown University Press, 2015).
 Parker, “Speech to the BfV Symposium in Berlin,”
 Andrew Parker, Speech, October 17, 2017, https://www.mi5.gov.uk/who-we-are-video-transcript.