Draft: March 18, 2002
please do not cite without permission
Prepared for presentation at the annual convention of the International Studies Association
New Orleans, March 24-27, 2002
This project was made possible by a grant from the Carnegie Corporation,
for which the author is extremely grateful
This paper examines international interventions in the aftermath of civil wars to see whether peace lasts longer when peacekeepers are present than when they are absent. Because peacekeeping is not applied to cases at random, I first address the question of where international personnel tend to be deployed. I then attempt to control for factors that might affect both the likelihood of peacekeepers being sent and the ease or difficulty of maintaining peace so as to avoid spurious findings. I find, in a nutshell, that peacekeeping after civil wars does indeed make an important contribution to the stability of peace.
Does peacekeeping work? Do international interventions to help maintain peace in the aftermath of civil war actually contribute to more stable peace? Since the end of the Cold War the international community and the UN have moved beyond Atraditional peacekeeping@ between states and have become much more involved in civil conflicts, monitoring and often managing or administering various aspects of transitions to peace within states.
Early optimism about the potential of the UN to help settle internal conflicts after the Cold War was tempered by the initial failure of the mission in Bosnia and the scapegoating of the UN mission in Somalia. The United States in particular now seems disillusioned with peacekeeping, favoring more aggressive (and less multilateral) peace enforcement in some cases (such as Kosovo), and a minimal international response in others (Rwanda, for example). Even in Afghanistan, where vital interests are now at stake, the US is reluctant to participate in, or even to encourage others who might contribute to a widespread peacekeeping mission.
Scholars and practitioners of peacekeeping have meanwhile been engaged in debate over the merits of the new wave of more Arobust@ and complex forms of peacekeeping and peace enforcement developed after the Cold War, and even over the effectiveness of more traditional forms of peacekeeping.1 However this debate is hampered by shortcomings in our knowledge about peacekeeping. In particular, the effectiveness of these interventions by the international community has not been rigorously tested. We do not have a very good idea of whether they really work.
Opponents of peacekeeping often point to dramatic failures that dominate news coverage of peacekeeping without acknowledging the success stories that make less exciting news. Proponents are also guilty of selection bias, however. The vast literature on peacekeeping compares cases and missions, but generally examines only cases in which the international community intervenes, not cases in which belligerents are left to their own devices. Surprisingly, very little work has been done to examine empirically whether peace is more likely to last in cases where peacekeepers are present than when they are absent.2
Moreover, the few studies that do address this empirical question, at least in passing, come to contradictory findings. In their study of peacebuilding in124 civil wars since World War II, Doyle and Sambanis find that Amultilateral United Nations peace operations make a positive difference.@3 In particular, they find strong evidence that multidimensional peacekeeping, i.e, Amissions with extensive civilian functions, including economic reconstruction, institutional reform, and election oversight@ significantly improve the chances of peacebuilding success. They find weaker evidence that observer missions and enforcement missions improve the chances for peace, but, surprisingly, that traditional peacekeeping has no effect on the chances for peacebuilding success.4
Hartzell, Hoddie, and Rothchild examine, among other things, the role of third-party enforcement on the duration of negotiated settlements to civil wars (also in the period since 1945). Their coding of third-party enforcement includes peacekeeping missions (as in Angola, El Salvador, and Mozambique, for example).5 They find that such third-party involvement significantly and substantially increases the duration of peace.
However, in a study using Doyle and Sambanis= data set but more sophisticated statistical techniques, Amitabh Dubey finds, inter alia, that third-party peacekeeping interventions, including that by the UN, has no significant effect on the duration of peace.6 In sum, of the three studies that examine whether peace lasts longer when peacekeepers are present than when they are absent, one finds that it does, one that it does not, and one finds that only some kinds of peacekeeping are effective. From the existing studies, it is not at all clear whether peacekeeping works. A closer look is clearly needed.
This paper examines peacekeeping in the aftermath of civil wars. I test the hypothesis that peacekeeping contributes to more durable peace, and the null hypothesis that it does not make peace significantly more likely to last. I look at both UN peacekeeping and peacekeeping by other organizations or ad hoc groups of states, and explore the effects of different types of peacekeeping: observer missions, traditional peacekeeping, multidimensional peacekeeping (all of which are based on the consent of the belligerents themselves), and peace enforcement (which is not).
This paper surveys civil conflicts in the period since World War II, but it focuses in particular on peacekeeping since the end of the Cold War. The peacekeeping role played by outsiders in civil wars changed drastically with the end of the Cold War. Between 1946 and 1988, the international community was generally not in the business of keeping peace between belligerents within states. The UN occasionally intervened in civil wars during this time period (in the Congo, Lebanon, and Cyprus), but these missions were intended in large part to contain civil conflicts that might otherwise draw in the great powers and/or to assist decolonization, not necessarily to keep peace between civil war belligerents themselves.7
Starting with the peacekeeping mission in Namibia in 1989 (UNTAG), however, the international community has attempted peacekeeping in many more civil wars. The practice of peacekeeping has changed accordingly, now generally involving much more extensive civilian components: electoral observation, police monitoring and training, and civilian administration. Since the Cold War, the primary purpose of peacekeeping has been to prevent the resumption of civil conflict. It is therefore likely that the relationship between peacekeeping and the duration of peace changed with the end of the Cold War.8
As noted above, to know whether peacekeeping makes a difference we need to look at the aftermath of all civil wars, not just those in which peacekeepers were deployed. From such a look it is not at all self-evident that peacekeeping works. A first glance at civil wars and peacekeeping does not bode well for judgments about the effectiveness of the international community=s attempts to maintain peace. Table 1 shows the relationship between peacekeeping and whether war resumes.9 The relationship is broken down in four ways: for all peacekeeping (top half), and for UN peacekeeping only (bottom); for the whole post-World War II period (left half) and only for the post-Cold War period (right).
[Table 1 about here]
Peacekeeping appears to make very little difference. Of the civil wars since 1944, there is another round of fighting between the same parties in about 42% when no peacekeepers were deployed, and in approximately 39% of those with peacekeeping. The numbers are even worse for UN peacekeeping, with peace slightly more likely to fail when UN peacekeepers are present than when they are absent. After the Cold War, the record of peacekeeping is slightly better, but in none of these cross tabulations is the difference between peacekeeping and no peacekeeping statistically significant. A breakdown by type of peacekeeping (Table 2) suggests that observer missions and multidimensional peacekeeping may reduce the likelihood of another war, but that traditional peacekeeping and enforcement missions do not.
[Table 2 about here]
But looks, especially first glances, can be deceiving. To begin with, these tables treat peace that falls apart many years down the line the same as peace that fails in a matter of months. The resumption of war in Rwanda in 1990 after 26 years of peace is considered just as much a failure as the renewed fighting in Rwanda in 1994 after less than a year of peace. This quick glance also does not take into account the fact that our data are Acensored.@ We know whether peace has lasted to date, but we do not know if it will continue to last in the future. Peace is holding for the time-being in Cambodia, for example, and in Northern Ireland, but these conflicts may yet flare up anew.10 Both of these problems can be dealt with using duration models, such as those employed in the analysis below.
However, the most important problem with the quick glance provided in Tables 1 and 2 is that peacekeeping is not applied to cases of civil war at random. If peacekeepers tend to deploy only to relatively easy cases, where peace is quite likely to last in any case, then looking just at whether peacekeepers were present and the duration of peace will lead us to overestimate any positive effect on peace. Almost as clichés, analysts of peacekeeping argue that the international community should only deploy Awhen there is peace to keep@ and when the parties exhibit Apolitical will@ for peace. This policy will help the UN and the international community to avoid embarrassing failures, but if pushed too far, it will also ensure the irrelevance of peacekeeping. On the other hand, if as is quite plausible, peacekeepers tend to be sent where they are most needed, when peace would otherwise be difficult to keep, this first glance at the cases may underestimate the effectiveness of peacekeeping.
Either way, to reach accurate assessments of the international community=s effectiveness at maintaining peace, we need to know something about the Adegree of difficulty@ of the various cases.11 And we need to know in what sorts of conflicts peacekeepers are likely to be dispatched. There have been a handful of studies examining the former question, and one (to my knowledge) on the second question.
What makes peace more or less likely to endure after civil wars? Peace is thought to be harder to maintain when war ends in a stalemate or compromise settlement than if one side achieves a military victory.12 On the other hand, peace that is ushered in with a formal peace settlement may be more stable than an informal truce.
Many have argued that identity conflicts are particularly intractable.13 Peace might therefore be harder to keep in conflicts that pit different ethnic or religious groups against each other as compared to wars fought over ideology. There is conflicting evidence on this count. Both Licklider and Doyle & Sambanis found identity wars to be more likely to resume than others, but Hartzell et. al. and Dubey found no significant difference.14 There is some evidence that the cost of war affects the durability of peace. Civil wars with higher death tolls have been found to be more likely to resume than less deadly conflicts.15 On the other hand, longer wars may be followed by more stable peace.16
Complicated wars involving many factions have been found to be harder to solve in a lasting way than wars with only two sides. And peace is harder to maintain in countries where a high level of economic dependence on natural resources means that there are easily Alootable@ goods (diamonds or oil, for example) that can drive continued conflict.17 The level of democracy in the country may also affect the durability of peace.18
Michael Gilligan and Stephen Stedman have examined where and when the United Nations tends to intervene. Their focus is on intervention during conflict, and on how quickly the international community responds to civil wars, but their study provides some insight into the selection issue of interest here. Most relevant for our purposes, they find that Aone of the best predictors of UN intervention is the number of deaths in a conflict,@ and strong evidence that the UN is less likely to intervene in countries with large government armies (i.e. militarily strong states). They find no clear evidence that the UN is more likely to intervene when a treaty has been signed, though they attribute this non-finding in part to problems of multicolinearity. They find that democracy, the war aims of the rebels (i.e. whether the war was secessionist), primary commodity exports, and whether the country is a former colony of a permanent member of the UN Security Council make no difference to the likelihood of UN intervention.19
That peacekeepers are more likely after very deadly conflicts (which are more prone to recurrent warfare), but not in strong states (which may be at less risk) suggests, not surprisingly, that the selection process for peacekeeping (whether they tend to be sent to easy or to hard cases) is fairly complicated. In the empirical analysis below, I examine first where peacekeepers are most likely to be deployed, with a focus on factors that are also likely to affect the stability of peace. Second, I examine the effects of peacekeeping on the durability of peace, controlling as much as possible for factors that might affect the Adegree of difficulty@ of the case.
This paper examines a data set consisting of 115 spells of peace (some of which are ongoing) in or after civil wars. The cases are listed in Appendix A. The data are adapted from the data set put together by Michael Doyle and Nicholas Sambanis (D&S for short).20 Their data cover civil wars that started after 1944 and ended, at least temporarily, before 1997. They define a civil war as an armed conflict that caused more than 1,000 battle deaths (total, rather than in a single year as in the Correlates of War definition); that represented a challenge to the sovereignty of an internationally recognized state; and occurred within the recognized boundary of that state; that involved the state as one of the principal combatants; and in which the rebels were able to mount an organized military opposition to the state and to inflict significant casualties on the state.
Ideally, to test the effects of peacekeeping on maintaining peace, we would want information on every cease-fire in every civil war. Unfortunately, given the messy nature of most civil wars and, frequently, their stop-and-start nature, a comprehensive accounting of cease-fires does not exist. One of the benefits of using Doyle and Sambanis= data is that they attempted to code significant peacebuilding attempts, even if those attempts did not ultimately succeed in ending the war. In a few cases, I have also added observations (e.g. in Rwanda and Angola) for cease-fires missed in their list. However, the data used here undoubtedly omit a number of short-lived cease-fires. Because we are more likely to notice (and there is more likely to be information on) such ill-fated cease-fires when peacekeepers are present, this omission should tend to bias our findings away from the conclusion that peacekeeping works. That is, the data more likely omit failures of peace without peacekeeping than with it, so that if we had more comprehensive data we would find the stabilizing effects of peacekeeping to be greater.
The duration of peace, the main dependent variable of interest, is the time between the termination of fighting and the start of another war, if any, between the same parties.21 If no war has resumed, the duration of peace is considered censored on December 31, 1999. Of the 115 cases, 47, or just over 40% Afail@ with the eruption of another war.
Peacekeeping is coded using both dummy variables (any vs. none) and by category of peacekeeping mission (none, observer, traditional peacekeeping, multidimensional peacekeeping, peace enforcement). Separate variables capture UN missions only, non-UN missions only, and both combined.22 Peacekeeping is both a dependent variable (for the first part of my analysis), and an independent variable (for the second part). For use as a an independent variable, peacekeeping is coded as a time-varying covariate. That is, changes in mission type over time, or the termination of the mission are recorded. So, for example, Cambodia is coded as having a traditional peacekeeping mission at first, then a multidimensional peacekeeping mission starting in March 1992, and as having no peacekeeping after the withdrawal of UNTAC in September 1993. For use as a dependent variable, however, peacekeeping is coded just once, as the most extensive type of peacekeeping deployed during that peace spell.23
In the 115 civil wars examined here, international personnel were sent to keep the peace after 41 (7 during the Cold War, and 34 since 1989). The UN sent missions in 30 cases (all but 5 after the Cold War), and states or organizations other than the UN sent missions in 23 cases (all but 2 since 1989).24
Dummy variables based on D&S=s coding of the war=s outcome capture whether the fighting ended with a victory by one side (victory), or whether a peace treaty was signed (treaty). Inclusion of these two variables allow us to see differences between these categories and wars that end with an informal truce or cease-fire.25 A further dummy variable (wartype) distinguishes ethnic, religious, and identity conflicts from ideological, revolutionary or other wars. The cost of the war (logdead) is measured using the natural log of the number of people killed (both battle deaths and civilian deaths). The duration of the war (wardur) is measured in months. A dummy variable (faction) marks whether the war involved more than two factions. The level of development of the country is coded with a proxy based on per capita electricity consumption (develop), and Alootables@ or natural resource dependence is measured using primary commodity exports as a percent of GDP. Prior history of democracy is measured using the average Polity score over the five years before the war (gurrlag5), and the size of the government=s army is recorded (garm).26 Where Do Peacekeepers Get Sent?
Table 3 shows the results of logistic regressions in which the dependent variable is whether any peacekeeping mission (observer, traditional, multidimensional, or enforcement) was deployed after a civil war. The first column presents the results for the entire period 1947-1999. Columns two, three, and four show the results in the post-Cold War period (1989-1999) for all peacekeeping, UN peacekeeping, and non-UN peacekeeping respectively.27 Because the determinants of peacekeeping might be very different for different types of missions, Table 4 shows the results of logistic regressions for each mission category separately. In both tables, negative coefficients indicate factors that make peacekeeping less likely, positive coefficients indicate variables that are associated with peacekeeping deployments.28
[Tables 3 and 4 about here]
Not surprisingly, wars that end with a victory by either the government or the rebels are very unlikely to see UN peacekeepers deployed. There are no multidimensional peacekeeping
missions in cases of victory by one side, and other forms of peacekeeping are rare in such cases.29 (The exceptions are Congo in 1965, Haiti and Rwanda in 1994.) However, as the fourth columns of Tables 3 and 4 show, this relationship does not hold for non-UN peacekeeping, nor for enforcement missions (there is substantial overlap, almost half of the non-UN missions are enforcement missions). Here, the positive coefficients indicate that non-UN or enforcement interventions are, if anything, more likely when one side wins (though in neither case is this statistically significant).30
More surprising is the apparent non-finding for the treaty variable. In the only regressions for which it is statistically significant, the sign is the opposite of that expected. Remember that because of the way D&S code these variables, both the victory and treaty dummy variables show the difference from wars that end in an Ainformal truce@ (the omitted category in the victory/treaty/truce trichotomy). So while peacekeepers were deployed in over 60% of the cases that ended with a treaty, as compared to 11% of those that ended with a victory, they were sent to over 78% of those that ended in a truce. Whether a treaty actually makes peacekeeping less likely is not clear (the finding is not robust for UN and non-UN peacekeeping), but we can confidently reject the hypothesis that peacekeepers are more likely to intervene when a formal treaty has been signed.31
When we look at all mission categories together (Table 3), there is no statistically significant relationship between peacekeeping and identity conflicts. But interestingly, observer missions appear to be less likely in wars between groups defined by ethnicity or religion, while traditional peacekeeping forces are more likely in identity wars (Table 4). Given the well-known problems of distinguishing Aidentity@ wars from Aideological@ wars (for example, which is Angola? D&S code it as an identity conflict, but during the Cold War most outside observers dubbed it an ideological conflict), I am inclined to suspect that the difference between observer missions and traditional peacekeeping in this regard is spurious, but it is an intriguing finding, perhaps worthy of further investigation.
I find no strong evidence that the cost of war is related to the probability of UN intervention. The coefficient for the war=s death toll is positive in most cases, but only statistically significant for enforcement missions. The lack of a strong relationship stands in contrast to Gilligan and Stedman=s finding, noted above, that the UN tends to intervene more quickly in the most costly civil wars.32 And it suggests a disheartening possibility. Because Gilligan & Stedman use the total number of deaths in the war (rather than the number of deaths up to the point of intervention) as their independent variable, their finding may suggest not that the UN responds quickly to deadly wars, but rather that when the UN intervenes early in a conflict, the death toll tends to rise (this was dramatically the case, for example, in Rwanda where the genocide took place after UN intervention). The D&S data simply do not allow us to determine which way the causal arrows run.
There is no consistent relationship between the duration of war and the deployment of peacekeepers. Enforcement missions (and non-UN missions) are significantly less likely in long wars, while other types of missions are more likely after long conflicts.33
UN peacekeeping in general seems to be more likely when there are three or more factions in the fight than in simpler two-way conflicts, particularly after the Cold War, but when we look by mission type (in Table 4), this appears to be driven entirely by Chapter VII enforcement missions. In every enforcement case there were at least three parties to the conflict.34 For consent-based forms of intervention, more factions make peacekeeping less likely.
Since 1989, the UN has been less likely to send peacekeepers to states with a high dependence on primary commodity exports. However, this finding is not consistent across different types of missions, or for non-UN intervention which is, if anything, more likely in such states.35 During the Cold War levels of development (or at least of the electricity consumption proxy) were positively associated with the probability of peacekeeping, but this relationship drops away after the Cold War.
Higher levels of peacekeeping, particularly multidimensional peacekeeping, and non-UN peacekeeping are more likely in countries with higher levels of democracy before the war, but observer missions appear to be less likely in democracies.
Peacekeepers are much less likely to be deployed to states that have large armies. It is no surprise, of course that peacekeepers have not been deployed to civil wars within China or Russia, but this relationship is not simply a reflection of Security Council membership. Non-Council members with relatively large armies, such as Nigeria, Mexico, India, the Philippines have all resisted peacekeeping in their own civil wars, even as they have participated in them elsewhere. The only peacekeeping in a country with a larger than average army (for those that experience civil war) is the enforcement mission in Iraq, an exception that proves the rule.36
The answer to the question where do peacekeepers get sent is quite complicated. It depends on whether we are talking about UN peacekeeping or missions by other actors, and it depends on what type of peacekeeping we are interested in. In several respects, it appears that consent-based peacekeepers tend to get sent to the hard cases rather than the easy ones. Peace is generally more stable after decisive victories than after wars that end in a tie, and peacekeepers are usually deployed where there was no clear winner in the war. Moreover, peacekeepers are no more likely to deploy when belligerents have signaled their will for peace in a formal treaty. If renewed conflict is less likely in states with large armies, a hypothesis I will examine below, the fact that peacekeepers tend to shy away from militarily strong states also strengthens the conclusion that peacekeepers go where they are most needed rather than where peace is easy to keep in any case. But this may be offset somewhat by the tendency of consent-based missions to avoid many sided fights and countries with high levels of primary commodity exports, if peace is in fact harder to keep under these conditions.37