Testing the surge: Why did violence decline in Iraq in 2007?

International Security

Volumn 37, Issue 1, 2012, Pages 7-40

  Biddle, Stephen ^a   Friedman, Jeffrey A ^b   Shapiro, Jacob N ^c  

^a Defense Policy at the Council on Foreign Relations   (United States)

^b HARVARD UNIVERSITY   (United States)

^c PRINCETON UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 84874470320     PISSN: 01622889     EISSN: 15314804     Source Type: Journal    
DOI: 10.1162/ISEC_a_00087     Document Type: Article

References (167)

1. Casualty figures are from "Operation Iraqi Freedom," iCasualties.org, accessed July 25, 2011.
2. See, for example, Kimberly Kagan, The Surge: A Military History (New York: Encounter Books, 2009)
3. John McCain and Joe Lieberman, "The Surge Worked," Wall Street Journal, January 10, 2008
4. Max Boot, "The Truth about Iraq's Casualty Count," Wall Street Journal, May 3, 2008
5. James R. Crider, "AView from Inside the Surge," Military Review, Vol. 89, No. 2 (March/April 2009), pp. 81 88.
6. Craig A. Collier, "Now That We're Leaving Iraq, What Did We Learn?" Military Review, Vol. 90, No. 5 (September/October 2010), pp. 8893.
7. Bartle Bull, "Mission Accomplished," Prospect, October 27, 2007
8. Dale Andrade, Surging South of Baghdad: The 3d Infantry Division and Task Force Marne in Iraq, 20072008 (Washington, D.C.: U.S. Army Center of Military History, 2010).
9. See, for example, Austin Long, "The Anbar Awakening," Survival, Vol. 50, No. 2 (April/May 2008), pp. 6794.
10. Steven Simon, "The Price of the Surge," Foreign Affairs, Vol. 87, No. 3 (May/June 2008), pp. 5776.
11. Marc Lynch, "SunniWorld," American Prospect, September 13, 2007
12. Jim Michaels, A Chance in Hell: The Men Who Triumphed Over Iraq's Deadliest City and Turned the Tide of War (New York: St. Martin's, 2010).
13. Daniel R. Green, "The Fallujah Awakening: A Case Study in Counter-Insurgency," Small Wars and Insurgencies, Vol. 21, No. 4 (December 2010), pp. 591609.
14. Dick Couch, The Sheriff of Ramadi: Navy SEALs and the Winning of Anbar (Annapolis: Naval Institute Press, 2008)
15. Stanley Kober, "Did the Surge Work?" Daily Caller, July 16, 2010
16. Jon Lee Anderson, "Inside the Surge: The American Military Finds New Allies, but at What Cost?" New Yorker, November 19, 2009, pp. 5869.
17. Nir Rosen, "The Myth of the Surge," Rolling Stone, March 6, 2008, pp. 4653.
18. Following this literature, we use the phrase "Anbar Awakening" to refer both to the origins of the Sunni realignment in Anbar in the fall of 2006 and to the subsequent spread and maturation of this movement as "Sons of Iraq" (SOI) over the course of 2007. Note that, although the Awakening thus began before the surge, the overwhelming majority of SOIs joined after April 2007, well into the surge.
19. See, for example, Andrade, Surging South of Baghdad, pp. 209242.
20. Nils B. Weidmann and Idean Salehyan, "Violence and Ethnic Segregation: A Computational Model Applied to Baghdad," International Studies Quarterly, forthcoming.
21. Lawrence Korb, Brian Katulis, Sean Duggan, and Peter Juul, How Does This End? Strategic Failures Overshadow Tactical Gains in Iraq (Washington, D.C.: Center for American Progress, 2008).
22. John Agnew, ThomasW. Gillespie, Jorge Gonzalez, and Brian Min, "Baghdad Nights: Evaluating the U.S. Military 'Surge' Using Nighttime Light Signatures," Environment and Planning A, Vol. 40, No. 10 (October 2008), pp. 22852295.
23. Stephen Biddle, "Stabilizing Iraq from the Bottom Up," testimony before the U.S. Senate Foreign Relations Committee, April 2, 2008.
24. Stephen Biddle, Michael O'Hanlon, and Kenneth Pollack, "How to Leave a Stable Iraq: Building on Progress," Foreign Affairs, Vol. 87, No. 5 (September/ October 2008), pp. 4058.
25. Colin H. Kahl, "Walk before Running," Foreign Affairs, Vol. 87, No. 4 (July/August 2008), pp. 151154, which also credits congressional threats of withdrawal.
26. Carter Malkasian, "Did the Coalition Need More Forces in Iraq?" Joint Force Quarterly, Vol. 46, No. 3 (Summer 2007), pp. 120126.
27. Also emphasizing the Awakening along with the surge but without any explicit analysis of synergy are Bing West, The Strongest Tribe: War, Politics, and the Endgame in Iraq (New York: Random House, 2008)
28. Linda Robinson, Tell Me How This Ends: General David Petraeus and the Search for a Way Out of Iraq (New York: PublicAffairs, 2008)
29. Thomas E. Ricks, The Gamble: General David Petraeus and the American Military Adventure in Iraq, 20062008 (New York: Penguin, 2009).
30. Some observers have also argued that leadership targeting had brought the insurgency to its knees by late 2007
31. See, especially, Bob Woodward, The War Within: A Secret White House History, 20062008 (New York: Simon and Schuster, 2008)
32. See also Christopher J. Lamb and Evan Munsing, Secret Weapon: High-Value Target Teams as an Organizational Innovation (Washington, D.C.: National Defense University Press, 2011).
33. In principle, one could propose combinations other than the surge-Awakening thesis treated below. The explanations considered here are thus not a logically exhaustive set, but the four schools we discuss capture the main lines of debate in the literature to date; thus our analysis focuses on them.
34. British Army Field Manual, Vol. 1, pt. 10: Countering Insurgency, Army Code 71876, October 2009.
35. On the contours of this debate and how it has been influenced by the surge, see David H. Ucko, The New Counterinsurgency Era: Transforming the U.S. Military for Modern Wars (Washington, D.C.: Georgetown University Press, 2009), especially chap. 8.
36. For a sharply different view, see Gian P. Gentile, "Our COIN Doctrine Removes the Enemy from the Essence of War," Armed Forces Journal, January 2008, p. 39.
37. On Iraq's influence on the Afghanistan debate, see, for example, Jeffrey Michaels and Matthew Ford, "Bandwagonistas: Rhetorical Re-description, Strategic Choice, and the Politics of Counterinsurgency," Small Wars and Insurgencies, Vol. 22, No. 2 (May 2011), pp. 352384.
38. Stephen Biddle, "Iraq's Lessons in Afghanistan and Iraq," in Seyom Brown and Robert H. Scales, eds., U.S. Policy in Afghanistan and Iraq: Lessons and Legacies (Boulder, Colo.: Lynne Rienner, 2012), pp. 8998.
39. See, for example, the transcript of the presidential debate held on September 26, 2008, http://elections.nytimes.com/2008/president/debates/transcripts/first-presidential-debate.html.
40. For recent reviews of the literature, see Christopher Blattman and Edward Miguel, "Civil War," Journal of Economic Literature, Vol. 48, No. 1 (March 2010), pp. 357.
41. Stathis N. Kalyvas and Paul Kenny, "Civil Wars," in Robert A. Denemark, ed., The International Studies Association Compendium Project (Oxford: Blackwell, 2009).
42. For an exception, see Jeffrey Friedman, "Manpower and Counterinsurgency: Empirical Foundations for Theory and Doctrine," Security Studies, Vol. 20, No. 4 (December 2011), pp. 556591.
43. See, for example, Jeffrey C. Isaac, Stephen Biddle, Stathis Kalyvas, Wendy Brown, and Douglas A. Ollivant, "The New U.S. Army/Marine Corps Counterinsurgency Field Manual as Political Science and Political Praxis," Perspectives on Politics, Vol. 6, No. 2 (June 2008), pp. 347350.
44. SIGACT data were provided by the Empirical Studies of Conflict (ESOC) Project. For a full discussion, see Eli Berman, Jacob N. Shapiro, and Joseph Felter, "Can Hearts and Minds Be Bought? The Economics of Counterinsurgency in Iraq," Journal of Political Economy, Vol. 119, No. 4 (August 2011), pp. 766819.
45. Iraq's violence was never uniformly distributed over the country's 111 districts: the 25 that accounted for 90 percent of 2006 SIGACTs were localized in central and western Iraq, especially in Anbar, Baghdad, Diyala, and Salah ad Din Provinces. As our purpose is to explain why violence fell, the relevant explanatory universe thus consists of districts where there was violence to reduce, of which our interviews span the great majority. There is substantial variance in the scale and speed of reduction across these 25 districts; the 22 for which we have interviews cover districts with greater and lesser SIGACTs as well as faster and slower reductions, and are not subject to bias from selection on the dependent variable. Note that Iraq had 104 districts in 2004 (the start date for our violence data) but currently has 111, as several districts in the Kurdish regions have been split.
46. Interviewees responded to a general call for participation to students and faculty in mid-career education programs at the U.S. Army Command and General Staff College, Harvard University, and Marine Corps Base Quantico. Initial participants recommended other individuals, some of whom were then interviewed. No selection criteria were imposed beyond service in Iraq from 2006 to 2008. These student populations are large and diverse, with no reason to expect systematic correlation between membership and the nature of their experience in Iraq. We have no evidence of sample bias relevant to our analysis.
47. "Iraq Body Count," http://www.iraqbodycount.org/.
48. Our data were produced through a multiyear ESOC-IBC collaboration, which made several improvements to the publicly available IBC data, including more consistent district-level geocoding
49. For diagnostics and a complete discussion of these data, see Luke Condra and Jacob N. Shapiro, "Who Takes the Blame? The Strategic Effects of Collateral Damage," American Journal of Political Science, Vol. 56, No. 1 (January 2012), pp. 167187.
50. On process tracing, see Gary King, Robert Keohane, and Sidney Verba, Designing Social Inquiry: Scientific Inference in Qualitative Research (Princeton, N.J.: Princeton University Press, 1994), pp. 85 87, 225228.
51. Our approach constitutes what Alexander L. George and Andrew Bennett call "analytical process tracing," as distinct from detailed narrative description of event sequences.
52. George and Bennett, Case Studies and Theory Development in the Social Sciences (Cambridge, Mass.: MIT Press, 2005), p. 211.
53. We do not test the competing explanations in a regression framework for several reasons. First, many of the arguments have no obvious implications for variance between observable factors at fixed, comparable geographic units (e.g., district-months). Second, there is no systematic theaterwide data on important variables such as Awakening forces' availability. Third, and most important, there is no viable source of plausibly exogenous variation in critical variables such as coalition force levels or operational methods.
54. Note that "AOs," which are delineated by military formation boundaries, are rarely collinear with "districts," which are Iraqi political subdivisions. We use both units of analysis as appropriate.
55. Weidmann and Salehyan, "Violence and Ethnic Segregation," p. 4.
56. Douglas Ollivant, Countering the New Orthodoxy: Reinterpreting Counterinsurgency in Iraq (Washington, D.C.: New America Foundation, 2011), p. 11.
57. Replication data, additional details on the AOs, coding choices, and various robustness checks are provided in supplementary materials at http://esoc.princeton.edu.
58. Patrick Cockburn, "Who Is Whose Enemy?" London Review of Books, Vol. 30, No. 5 (March 2008), p. 14.
59. On the cleansing school, generally, see Weidmann and Salehyan, "Violence and Ethnic Segregation"
60. Korb et al., How Does This End?.
61. Agnew et al., "Baghdad Nights." This argument draws on a theoretical tradition that sees security dilemmas involving comingled populations as a major source of violence.
62. See, for example, James D. Fearon and David D. Laitin, "Explaining Interethnic Cooperation," American Political Science Review, Vol. 90, No. 4 (December 1996), pp. 715735.
63. Barry R. Posen, "The Security Dilemma and Ethnic Conflict," Survival, Vol. 35, No. 1 (Spring 1993), pp. 2747.
64. Chaim Kaufmann, "Possible and Impossible Solutions to Ethnic Civil Wars," International Security, Vol. 20, No. 4 (Spring 1996), pp. 136175.
65. Alexander B. Downes, "The Problem with Negotiated Settlements to Ethnic Civil Wars," Security Studies, Vol. 13, No. 4 (Summer 2004), pp. 230279.
66. the special issue of Security Studies, Vol. 13. No. 4 (Summer 2004).
67. Rui J.P. de Figueiredo Jr. and Barry R. Weingast, "The Rationality of Fear: Political Opportunism and Ethnic Conflict," in Barbara Walter and Jack Snyder, eds., Civil Wars, Insecurity, and Intervention (New York: Columbia University Press, 1999).
68. Of course, sectarian Sunni versus Shiite killings made up only part of Iraq's violence-it excludes, for example, the Iraqi versus U.S. fighting that loomed so large for the U.S. debate. In addition, the relative prevalence of sectarian and nonsectarian violence varied both geographically and temporally. The cleansing school is rarely explicit on what aspects of this violence it seeks to explain.
69. The following discussion is based entirely on original interviews with coalition officers who served in Baghdad during the period in question
70. Of course, no human population is literally homogeneous in the sense that its makeup is absolutely uniform. There are always exceptions, and our usage is not meant to exclude this. By "homogeneous," we mean a substantial preponderance of one sect over another, following the characterizations provided by our interviewees and in demographic analyses such as the Gulf 2000 Project.
71. This does not constitute a general refutation of security dilemma theories of ethnosectarian violence in Iraq or elsewhere. We do not claim that fear was unimportant in causing violence in Iraq. What the evidence does establish, however, is that the pattern of violence offers no logical basis for Iraq's bloodshed to fall suddenly in mid-2007, whether the motive for that violence was fear or greed. By mid-2007, conquest, not unmixing, was dominant in Baghdad's sectarian warfare, and Shiites' conquest of the city was incomplete and apparently ongoing when the level of violence fell.
72. U.S. Army Military History Institute, Iraq Surge Collection (henceforth MHI) audio files 10, 17, 23, 35, and 55.
73. MHI audio files 11, 18, 26, 36, 38, 55, and 61
74. MHI audio files 11, 18, 38, and 55. Mansour's and Karkh's size and population were calculated from LandScan 2008 data. Similar patterns characterized violence east of the Tigris. In Rusafa, for instance, Sunnis lived mostly in mahala-sized clusters such as the roughly 3.5-square-kilometer Sheikh Omar neighborhood. This was divided from the Shiite sections of al-Fadl to the south by a market known as "Line Square." The Sheikh Omar neighborhood's perimeter was walled; Line Square was defended on both sides with barriers and snipers; and this is where the sectarian violence mainly occurred. MHI audio file 14. In the Madain district south of Baghdad, the sects were also largely divided into homogeneous clusters, with Sunnis living to the north and Shiites to the south. Violence largely took place along this fault line, with JAM evicting Sunnis and emplacing squatters as they left. MHI audio file 51.
75. On the Awakening thesis, see Long, "The Anbar Awakening"
76. Simon, "The Price of the Surge"
77. Lynch, "Sunni World"
78. Michaels, A Chance in Hell
79. Green, "The Fallujah Awakening"
80. Couch, The Sheriff of Ramadi
81. Kober, "Did the Surge Work?"
82. Anderson, "Inside the Surge"
83. Rosen, "The Myth of the Surge."
84. Secondary literature is cited where relevant, but the description of previous Awakening attempts is again solely based on original interviews
85. MHI audio file 48. See also Timothy S. McWilliams and Kurtis P. Wheeler, eds., Al-Anbar Awakening, Vol. 1: American Perspectives: U.S. Marines and Counterinsurgency in Iraq, 20042009 (Quantico, Va.: Marine Corps University, 2009), pp. 54, 62.
86. Steve Negus, "Home-Grown Police Force Takes On Iraq Insurgents," Financial Times, March 31, 2006
87. Nelson Hernandez, "Iraqis Begin Duty with Refusal
88. Some Sunni Soldiers Say They Won't Serve outside Home Areas," Washington Post, May 2, 2006
89. MHI audio file 48. See also Long, "The Anbar Awakening," p. 78.
90. James A. Russell, Innovation, Transformation, and War: Counterinsurgency Operations in Anbar and Ninewa Provinces, Iraq, 2005 2007 (Stanford, Calif.: Stanford University Press, 2011), p. 60.
91. Gary W. Montgomery and Timothy S. McWilliams, eds., Al-Anbar Awakening, Vol. 2: Iraqi Perspectives: From Insurgency to Counterinsurgency in Iraq, 20042009 (Quantico, Va.: Marine Corps University, 2009), p. 142.
92. Malkasian, "Did the Coalition Need More Forces in Iraq?" p. 123.
93. Later, after U.S. Operations Steel Curtain and Steel Curtain II cleared al-Qaim in November 2005, U.S. forces reengaged the Albu Mahal in holding the area, but the Hamza Brigade had effectively been disestablished. MHI audio file 48.
94. MHI audio files 29 and 48
95. MHI audio files 46 and 48
96. See also McWilliams and Wheeler, Al-Anbar Awakening, Vol. 1, pp. 114, 125126.
97. Niel Smith and Sean MacFarland, "Anbar Awakens: The Tipping Point," Military Review, Vol. 88, No. 2 (March/April 2008), pp. 4152.
98. See, for example, Paul Staniland, "Between a Rock and a Hard Place: Insurgent Fratricide, Ethnic Defection, and the Rise of Pro-State Paramilitaries," Journal of Conflict Resolution, Vol. 56, No. 1 (February 2012), pp. 1640.
99. Stathis N. Kalyvas, The Logic of Violence in Civil War (New York: Cambridge University Press, 2006).
100. See, for example, MHI audio files 4, 9, 15, 18, 23, 25, 35, 37, 40, 45, 48, 49, 50, and 69
101. Pre-surge U.S. troop strength averaged 135,000 to 140,000, and exceeded 145,000 in only seven of the forty-three months between August 2003 and February 2007.
102. Michael O'Hanlon and Ian Livingston, "Iraq Index: Tracking Variables of Reconstruction & Security in Post-Saddam Iraq" (Washington, D.C.: Brookings Institution, August 2011), p. 13, http://www.brookings.edu/saban/ iraq-index.aspx, accessed March 6, 2012.
103. U.S. troop strength while the Anbar People's Council and the Desert Protectors were active averaged 150,000 to 155,000; neither of the other pre-surge realignment attempts occurred with more than 140,000 U.S. troops in Iraq.
104. Note that the fall 2006 Anbar realignment that initiated the Awakening occurred in Col. Sean MacFarland's AO, where one of the occasional early experiments with Petraeus-like methods was ongoing. The surge brought such methods across the theater, and was thus instrumental in the Anbar Awakening's ability to spread beyond its origin in this AO.
105. The description below is drawn from Kagan, The Surge
106. McCain and Lieberman, "The Surge Worked"
107. Boot, "The Truth about Iraq's Casualty Count"
108. Crider, "A View from Inside the Surge"
109. Collier, "Now That We're Leaving Iraq, What DidWe Learn?"
110. Bull, "Mission Accomplished"
111. Andrade, Surging South of Baghdad
112. Examples include Operations Iron Reaper and Iron Harvest, which we discuss in more detail below. Many analysts also emphasize concomitant improvements in Iraqi Security Forces (ISF), which they believe provided much of the surge's effective strength.
113. See, for example, Kagan, The Surge, pp. 137165.
114. Here we treat the ISF buildup and U.S. reinforcements together as the surge, though Iraqi methods and skills lagged far behind the Americans' throughout 2007. Note that the surge's main effort was initially in Baghdad with additional forces deployed to Anbar and Diyala. The resulting increase in troop density was felt more broadly over time, as the stabilization of areas to which the surge brigades initially deployed enabled forces to be moved elsewhere.
115. The account below is drawn from Biddle, "Stabilizing Iraq from the Bottom Up"
116. Biddle, O'Hanlon, and Pollack, "How to Leave a Stable Iraq"
117. Kahl, "Walk before Running"
118. Malkasian, "Did the Coalition Need More Forces in Iraq?"
119. For troop counts, see O'Hanlon and Livingston, Iraq Index, pp. 13, 17.
120. The Jones Commission, tasked by the U.S. Congress with assessing ISF capability and potential, put it this way in September 2007: "The challenge for the [Iraqi] Army is its limited operational effectiveness, caused primarily by deficiencies in leadership, lack of disciplinary standards, and logistics shortfalls." Iraqi police rated even harsher assessments: "In general, the Iraqi Police Service is incapable today of providing security at a level sufficient to protect Iraqi neighborhoods from insurgents and sectarian violence.. .. The National Police have proven operationally ineffective, and sectarianism in these units may fundamentally undermine their ability to provide security. The force is not viable in its current form." The Commission saw the ISF as improving, but far from effective, in 2007.
121. Gen. James L. Jones, U.S. Marine Corps, chairman, The Report of the Independent Commission on the Security Forces of Iraq (Washington, D.C.: Center for Strategic and International Studies, September 6, 2007), pp. 910.
122. This is especially true given that the U.S. military fell well short of its own doctrinal standard that successful counterinsurgents require 20 troops per 1,000 civilians to be protected. Headquarters, Department of the Army, FM 3-24: Counterinsurgency (Washington, D.C.: U.S. Government Printing Office, December 2006), par. 1-67. Iraq's population is roughly 30 million.
123. Central Intelligence Agency, The World Factbook: Iraq, https://www.cia.gov/library/publications/the-worldfactbook/ geos/iz.html, accessed March 30, 2012.
124. FM 3-24 thus implies a need for about 600,000 soldiers in Iraq-and, as discussed earlier, it is unclear how much the ISF contributed to the effort. The utility of FM 3-24's standard is questionable (see Friedman, "Manpower and Counterinsurgency"), but even those who accept it would have little reason to expect that the surge bumped coalition troop density above some critical threshold in Iraq.
125. Most interviewees with firsthand knowledge of SOIs reported that these units contained former insurgents, not just in Anbar but across central Iraq, including Al Dur, Awja, Baladrooz, Habbaniyah, Hit, Kirkuk, Narwan, Northern Babil, Northwest Wasit, Rawah, Salman Pak, South Diyala, Tikrit, and Wynot, and the Baghdad neighborhoods of al-Rusafa, Amiriyah, Dora, East Rashid, Khadamiya, Madain, Mahmoudiya, Sayidiyya, and Tarmia. MHI audio files 4, 711, 13, 18, 20, 2326, 30, 35, 41, 43, 49, 51, 53, 54, 63, 64, 68, and 69.
126. The discussion here follows the synergy literature; it focuses on the JAM as the most important of the Shiite militias and one whose military incentives mirrored those of its rivals
127. On other Shiite militias, see Michael Harari, Status Update: Shi'a Militias in Iraq (Washington, D.C.: Institute for the Study ofWar, 2010).
128. Anthony Cordesman, The Iraqi Insurgency and the Risk of Civil War: Who Are the Players? (Washington, D.C.: Center for Strategic and International Studies, 2006).
129. Patrick Gaughen, "Backgrounder #17: The Fight for Diwaniyah: The Sadrist Trend and the ISCI Struggle for Supremacy" (Washington, D.C.: Institute for the Study of War, 2007).
130. Anthony Shadid, "In a Land without Order, Punishment Is Power: Conflicts among Shiites Challenge a Village Sheikh in Southern Iraq," Washington Post, October 22, 2006
131. An exception was the post-2007 combat between Sadr's JAM and coalition forces during the Iraqi government's spring 2008 "Charge of the Knights" offensive in Basra and the follow-on operations in Amarah and Sadr City. This offensive led to a brief spike in violence, which quickly subsided when Sadr again stood down in a cease-fire negotiated with Nouri al-Maliki's government after the JAM proved unable to hold; the 2008 cease-fire's logic was similar to its 2007 predecessor's, and the 2008 violence did not produce more than a temporary exception to the trend of radical violence reduction after 2007.
132. On the Charge of the Knights offensive and ensuing combat, see Marisa Cochrane, The Battle for Basra, Iraq Report, No. 9 (Washington, D.C.: Institute for the Study of War, June 23, 2008).
133. In the two AOs where interviewees rotated out before the SOIs stood up, we used Iraq Reconstruction Management System data to identify the date of first payments to SOIs in that AO
134. For a description of these data, see Berman, Shapiro, and Felter, "Can Hearts and Minds Be Bought?"
135. The independent variable for these regressions is time; the dependent variable is monthly SIGACTs as a percentage of the maximum value that AO experienced from 2004 to 2008. This normalization facilitates cross-AO comparisons, because a drop of 10 SIGACTs per month could be a major change in a quiet AO, but a marginal change elsewhere. Thus, an estimated coefficient of _0.06 would show violence declining in that AO by six percentage points per month. Two AOs produced equal coefficients before and after SOI standup; these ties were broken by examining one- and two-month intervals (see table 1).
136. All regressions and supporting data are available at http://esoc.princeton.edu.
137. These findings are robust to a variety of alternative specifications. When we examine other intervals of equal length before and after SOI standup, the SOIs correlate with faster rates of violence reduction. If we were to shorten the intervals to two months, for example, the SOIs' apparent impact would increase, with violence declining on average by 1.2 percentage points per month prior to SOI standup and by 5.8 percentage points thereafter. There is no interval between one and twelve months for which the violence reduction rate does not increase by at least a factor of 1.9 after SOIs stand up. Nor do the intervals need to be symmetric to support synergy: when the slope of violence is computed for any interval from one to twelve months after SOI standup, it falls faster on average across all 38 AOs than it does for any interval from one to twelve months prior to SOI standup. We also examined the robustness of these results by dropping all SIGACTs that were positively identified as not occurring from combat. All of these patterns remained substantively the same: for example, violence fell by 6.2 percentage points per month on average in the three months following standup, versus 2.5 in the three months prior. Across a range of intervals and ways of measuring insurgent attacks, violence thus drops faster after SOI standup.
138. Table 2 also demonstrates that, for AOs where SOIs stood up during 2007, 69 percent support the synergy thesis, with a fivefold acceleration in violence reduction
139. Table 2 demonstrates that results also become more confirmatory when one examines the 19 AOs where violence was highest in the month of SOI standup
140. See MHI audio files 4, 9, 15, 18, 23, 25, 35, 37, 40, 45, 48, 49, 50, and 69
141. Note that casualty rates in COIN often increase following reinforcements, then decline thereafter; this was so in Iraq in 2007, where U.S. casualties peaked three months into the surge in May 2007. "Operation Iraqi Freedom," iCasualties.org. In principle, this "darkest before the dawn" phenomenon could bias post-SOI violence reduction rates downward: if the pre-SOI slope calculation straddled a crest in violence, this would artificially increase the apparent synergy confirmation rate, but this did not happen here. In only 2 AOs (Sayidiyya and Radwaniyha) did violence peak within the three-month window prior to SOI standup, and only the Sayidiyya AO was otherwise confirmatory (and thus subject to potential confirmation bias). Moreover, per note 51, SOIs correlate with accelerated violence reduction no matter what intervals we analyze, indicating that local maxima prior to SOI standups are not confounding the analysis either. Nor is our analysis confounded by violence trends that were already declining at an accelerating rate prior to SOI standup. Violence trends across these 38 AOs are actually weakly convex: if we regress monthly violence on time elapsed since violence peaked in each AO, then a second-order term for duration has a positive coefficient that is statistically significant at the p _ 0.001 level, no matter what time period the regression covers. These patterns all indicate that the results presented here are not simply artifacts of nonlinear violence trends.
142. MNF-I Public Affairs Office, "Last 'Surge' Brigade Redeploys," Press Release, No. 20080708-08, July 9, 2008.
143. MHI audio files 24, 30, and 65
144. MHI audio files 18 and 63
145. MHI audio file 45
146. MHI audio file 24
147. We operationalized pre-surge violence in each AO as the average of monthly SIGACTs from September 2006 through December 2006
148. See, for example, Max Boot, Frederick Kagan, and Kimberly Kagan, "How to Surge the Taliban," New York Times, March 12, 2009
149. Alissa J. Rubin, "Afghan Program Adds Local Units to Resist Taliban," New York Times, July 15, 2010.
150. Anand Gopal and Yochi J. Dreazen, "Afghanistan Enlists Tribal Militia Forces," Wall Street Journal, August 12, 2009.
151. Peter Mansoor and Max Boot, "Winning in Afghanistan," Los Angeles Times, December 16, 2010
152. On the APPP and ALP programs, see Seth G. Jones and Arturo Muñoz, Afghanistan's LocalWar: Building Local Defense Forces (Santa Monica, Calif.: RAND, 2010).
153. Mathieu Lefèvre, Local Defence in Afghanistan: A Review of Government-Backed Initiatives (Kabul: Afghanistan Analysts Network, 2010)
154. Alex Rodriguez, "Anti-Taliban Tribal Militias Come with Baggage," Los Angeles Times, June 19, 2010
155. Rubin, "Afghan Program Adds Local Units to Resist Taliban."
156. See Headquarters, Department of the Army, FM 3-24. Note that, although the manual does see COIN as a competition in governance, the phrase "hearts and minds" appears only once, in an appendix, paragraph A-26.
157. This is not to say that local civilians' decisions played no role on the margins see, e.g., Berman, Shapiro, and Felter, "Can Hearts and Minds Be Bought?".
158. Condra and Shapiro, "Who Takes the Blame?"), just that these decisions cannot explain Iraq's overall violence trends
159. Many interviewees reported tensions between the ISF and SOIs; these tensions sometimes escalated into violence, with SOIs often demanding protection from the ISF. For examples, see MHI audio files 1, 3, 6, 13, 24, 26, 36, 37, 51, and 68.
160. On governance reform's importance for Afghanistan, see, for example, Stephen Biddle, "The Difference Two Years Make," American Interest, Vol. 7, No. 1 (September/October 2011), pp. 4049.
161. On surge brigades' sometimes lavish use of firepower in 2007, see, for example, Andrade, Surging South of Baghdad, pp. 129, 249, 317320.
162. on its importance, see, for example, MHI audio file 69
163. For points of departure in such research, see Fotini Christia, "The Closest of Enemies: Alliance Formation in the Afghan and Bosnian Civil Wars," Ph.D. dissertation, Harvard University, 2008.
164. Paul Staniland, "Explaining Cohesion, Fragmentation, and Control in Insurgent Groups," Ph.D. dissertation, Massachusetts Institute of Technology, 2010.
165. For exceptions, see Friedman, "Manpower and Counterinsurgency," on troop density
166. Jason Lyall and Isaiah Wilson III, "Rage against the Machines: Explaining Outcomes in Counterinsurgency Wars," International Organization, Vol. 63, No. 1 (Winter 2009), pp. 67106, on doctrine and equipment.
167. Andrew Enterline and Joseph Magagnoli, "Reversal of Fortune? Strategy Change and Counterinsurgent Success by Foreign Powers in the Twentieth Century," unpublished manuscript, University of North Texas, January 29, 2010, on doctrine