Finally, temporal distinctions must be made.  This article=s periodization was designed to meet two criteria.  First, roughly equal periods of time were sought, since comparable segments allow for easier  interpretation.  Second, given the dramatic geopolitical changes of the last decade, the Cold War and the post Cold War periods were differentiated.  Both criteria were met by slicing the forty-four Cold War years included in the Pearson-Baumann collection into three approximately equal fifteen year segments: 1946-1959; 1960-1974; and 1975-1989.   The final period analyzed, the post Cold War era, is dated from 1990-1996.  Roughly half the length of the Cold War time periods, it remains readily comparable.  Except for the 1990 break-point, none of this study=s temporal markers represent watersheds in international politics.  Rather, this periodization has been fashioned to facilitate the comprehension of trends in belligerent and territorial force without the variability associated with annual or decadal measures.  To simplify their presentation, these four time periods are designated t1 (1946-1959), t2 (1960-1974), t3 (1975-1989), and t4 (1990-1996).

Methods

Logistic regression is employed because the dependent variables are dichotomous.  Also, this method has the advantage of placing as much emphasis on the effects of the independent variables as predicting the value of the dependent variable.  This study focuses on comparison across regions and temporal domains C that is, its principal concern is trends and variations among the independent variables.  Moreover, the logistic model has the practical attraction of offering a precise interpretation of independent variable effects.  This is accomplished by calculating the relationship between the variables as an odds-ratio.  In the logistic model, odds-ratios indicate the impact that an independent variable has on the dependent variable in comparison to a reference category.  Neutral reference categories are added to the logistic models in this study.  To analyze belligerent force, for example, a reference category that is evenly divided between belligerent and non-belligerent uses of force is included in the model.  It makes it easy to determine whether actors in a subsystem have a greater propensity to use belligerent or non-belligerent force.  Essentially, an odds ratio of 1 in this paper indicates that the subsystem in question (the independent variable) has an effect on belligerent force (the dependent variable) that is similar to the reference group.  Since the reference category is evenly divided between belligerent and non-belligerent uses of force, this means that interveners within that subsystem are statistically as likely to use belligerent as non-belligerent force.  An odds-ratio larger than 1 illustrates how much greater the odds are that the interventionary force used within that subsystem is belligerent.  For example, an odds ratio of 2.5 indicates that forceful interactions in that region are two and a half times more likely to involve belligerent than non-belligerent force.  If, on the other hand, the odds-ratio is below 1, non-belligerent uses of force are more likely than belligerent actions.  The odds-ratio is not affected by shifts in sample size and, by offering a readily interpretable comparison of the extent that force is motivated by belligerent or non-belligerent issues in different subsystems, it underscores the practical, substantive significance of the findings.

 

Reviewing the Empirical Evidence

This study=s findings are presented in three stages.  First, patterns of belligerent force and territorial force are traced for the international system=s center.  The center offers a useful test case for the issue dichotomy analyzed in this article.  If the center has grown more peaceful over the past half-century as is often suggested, center states= use of belligerent and territorial force should be decreasing.  Second, the proportion of interventionary uses of force launched over belligerent issues and over territory are mapped across regional subsystems in a series of charts.  These figures provide vivid images of the differences in the use of belligerent force across regions.  Third, logistic regression models estimate the statistical significance of these regional patterns, and whether the proportion of forceful interactions over either belligerent or territorial issues has changed significantly over time.
The utility of the issue dichotomy used in this study is apparent in Figure 1.  This figure illustrates the percentage of center uses of force motivated by non-belligerent and territorial issues.  Presenting non-belligerent rather than belligerent force makes the interpretation of Figure 1 and the graphs to follow easier.  As expected in the literature on the emergence of a zone of peace in the center, non-belligerent uses of force have been steadily rising over the past half-century (as a percentage of all interventions coded for belligerent force).  Since belligerent scores are by definition the inverse of non-belligerent outcomes (that is, the non-belligerent result of 87% for the center from 1990-96 means that 13% of reported interventions were over belligerent issues), belligerent force has correspondingly been on the wane.  When center states use military force, it is increasingly less likely that they do so over issues that directly challenge the recipient state.  In fact, almost one half (47%) of center military interventions in the post-Cold War era were motivated by humanitarian concerns, nearly all of which were supported by the host government.  Beyond this, First World states are also becoming less embroiled in squabbles over the most pugnacious issue in world politics, territory.  As Figure 1 illustrates, center deployments of interventionary force over territorial issues have trended downward since 1946, to the point that only 5% of center military interventions were driven by territorial issues from 1975-1989, and none were after 1990.  It must be emphasized that this figure charts all interventions by center actors, not just those that occurred within the center subsystem.  An analysis of the latter would include only two cases B the Cod War episodes between Britain and Iceland in 1958 and 1975.

Figure 1.
 

The fairly stark decline in belligerent and territorial deployments of force underscores that the center has not only become a place where force is rarely, if ever, used locally, center actors have also become much less likely to use bellicose military force abroad.  Their military actions therefore stand less chance of breeding resentment within the target country or of producing larger conflicts.  In short, center military deployments appear to have become more cautious and perhaps less conflict-inducing.
The reasons for this evolution are both numerous and largely beyond the scope of this article.  Nonetheless, a number of potentially overlapping explanations are evident.  The reluctance of the most prolific center intervener, the United States, to accept significant casualties in its post-Vietnam military deployments may partly explain the inclination to avoid belligerent force.  Particularly in the post-Cold War era, the U.S. has used unilateral military force only when it has had the ability to draw on overwhelming numbers of troops, not to mention sophisticated firepower (Pickering, 1999).  The domestic political costs of military missions abroad are also becoming more salient for center decision-makers.  Rally round the flag surges in support of military ventures tend to evaporate rapidly, and military actions that fail to produce quick and bloodless results can prove costly in later elections (Cotton, 1986; Gelpi and Grieco, 1998).  Concerns over casualties and battlefield embarrassments have only been heightened by the steady growth in the conventional and the non-conventional arsenals of developing countries over the past decade.
Figures 2-6 display patterns in the use of non-belligerent force in other regional subsystems.  It should be noted that some subsystems register too few uses of force for accurate graphing in the early Cold War period (when many states remained colonial appendages) and in the shorter post-Cold War period.  A mere glance at these figures is enough to see that patterns do diverge, sometimes markedly.  With the exception of South Asia, the proportion of military interventions motivated by non-belligerent issues was much lower in Asia and South America than in Africa.  The Middle East lies somewhat in between the other regions on this score, while the Eastern European figures vacillate wildly, a finding surely related to the political and economic transformations that have swept across this region the last decade and a half.  Similar results emerge in Figures 7-11, which portray the proportion of uses of force that were motivated by territorial issues.  South America and East Asia again stand out.  Both regions have a high percentage of interventions motivated by territorial concerns, although the South American pattern fluctuates considerably.  In contrast, actors in Central America, most all African subsystems, especially Central and Southern Africa, and to a lesser extent Eastern Europe and the Middle East use territorial force infrequently.
The prevalence of belligerent and territorial force in South America is explained by two well-documented rivalries over disputed territories.  The first is between Ecuador and Peru over their Andean border; the second is between Argentina and Britain over the Falklands/Malvinas Islands.  The rivalry between Ecuador and Peru accounts for nearly thirty-one percent of all uses of force within South America over the past fifty years, and that between Argentina and Britain accounts for a further nine percent.  Little wonder that when looking at the proportion of interventions that are generated by belligerent issues or territory that South America appears a rather bellicose regional subsystem.  Any such claims must be put into perspective, however.  Although the ratio of force used over belligerent and territorial issues to that used over non-belligerent and non-territorial issues is high in this subsystem, the overall rate of intervention is fairly low.  South America ranks roughly in the middle of the thirteen subsystems studied for the total number of belligerent interventions and the number of belligerent interventions per actor from 1946 to 1996.  Unresolved territorial disputes also fuel the bellicose use of force in a second contentious subsystem, East Asia.  The sources of these disputes are well known, namely the Chinese claim on Taiwan, the Korean divide, and the tensions that persist over island groupings in the South China Sea such as the Spratleys.  Over forty-four percent of all uses of force initiated by East Asian actors over the past half-century have involved China and one or more of its neighbors in a territorial dispute.
Other subsystems seem to be evolving away from the use of force over belligerent issues.  Sub-Saharan Africa is noticeable in this regard.  It has comparatively low proportions of both belligerent and territorial interventions.  The reasons for this seemingly propitious finding are evident.  One is that a relatively high percentage of external interventions into this region have been supportive, often taking the form of humanitarian operations to limit the effects of civil strife or natural disaster.  Perhaps more important is the norm against hostile intervention that was deeply embedded within most sub-Saharan African states in the years following independence.  This norm developed in response to the inherent fragility of many of the states in the region.  Decision-makers have been reluctant to use armed force across borders because doing so might result in external meddling among divisive factions at home -- a potentially explosive situation.  Thus, the volatile issue of territory has often been removed from interstate disputes in subSaharan Africa (see Jackson and Rosenberg, 1982). There is, however, evidence that the non-intervention norm may be eroding.  The increase in territorial force in t4 (see Figure 8) illuminates this possibility, as does the intervention of local states into the ongoing Congolese civil war (which began after 1996 and hence is not included in this analysis).  
Notable trends away from belligerent force are also present in Central America and Eastern Europe.  The use of force over territory is rare in the former, while the latter has witnessed some decline in the proportion of belligerent and territorial interventions since 1975.  Of all subsystems, the Middle Eastern pattern is perhaps least anticipated.  Actors in the Middle East have been less motivated by territorial issues than counterparts in a number of other regions, and they have employed comparatively low levels of belligerent force since 1975.  The absence of Arab-Israeli warfare and the increase in supportive center missions (notably during the Persian Gulf War) help explain the rise in non-belligerent force in t3 and t4.  Conspicuous patterns are not evident in other subsystems.
Figures 1-11 highlight regional trends in belligerent and territorial force, but they provide no indication of how significant regional variations are, or whether the propensity to intervene over belligerent issues or over territory has altered in the past half-century.  The logistic regression models in Table 1 provide initial answers to these questions.  To measure the variation among regional subsystems, these subsystems are employed as independent variables.  Belligerent force and territorial force are the dichotomous dependent variables.  As noted above, subsystems are not compared directly to one another.  They are compared to neutral reference groups.  In Model 1, the

Figures 2-6.  Percent of Military Interventions Motivated by Non-Belligerent Issues

 

  Figure 2.                                                                                        Figure 5.

 

 Figure 3.                                                                                          Figure 6.

 

 Figure 4.

 

Figures 7-11.   Percent of Military Interventions Motivated by Territorial Issues

    Figure 7.                                                                                         Figure 10.

                                 
    Figure 8.                                                                                         Figure 11.

   

    Figure 9.

 

reference group is split evenly between uses of force over belligerent and non-belligerent issues, while in Model 2 it is equally divided between uses of force over territorial and non-territorial issues.  These reference categories make it easy to determine if actors in a

Table 2. Significant Results of Logistic Regression Estimates of Regional Variation in Belligerent Force

        t1t2                                 t3                            t4       

Center                                -37.47***                                                                          -2.27***      
                     (1.10)                                                     (.57)
Central America                                                                                                              
                                                                                                                
South America                                                  2.59**
                                                (1.01)
West Africa                                                      2.99*                         
                                                (1.50)
Central Africa                                                                                   -2.37**
                                                                                   (.94)
East Africa                              

Southern Africa                                                                                                            -1.88*
                                                                                   (.91)
Northern Africa                      

Middle East                        -36.87***              2.54**                                                                       -2.50*
                       (.79)                    (.97)                                                    (1.22)
East Asia                                                           2.43*
                                                (1.10)
South Asia                                                        2.32*                                                     2.54*
                                                (1.01)                                                    (1.33)
Southeast Asia                    -38.44***
                     (1.35)
Eastern Europe                                   

Constant                              37.34***             -2.24*                          .87                    -2.73*
                       (.72)                    (.96)                          (.84)                   (1.19)
Chi-square                           55.78***            26.17**                                                 35.90***       16.69*
Log-likelihood                    -39.04                 -80.81                        -90.08                 -44.50
% Correctly Predicted          77.55                  68.84                        71.60                    71.91

* p < .05; ** p < .01; *** p < .001.  Two-tailed tests.  Standard errors in parentheses.

1 Ns reported in different time periods (t1-t4) mirror the total N=s for the given periods, adding a previously explained neutral control group.  In addition, likelihood ratio tests were run for each of the above models (t1-t4), all of which indicated that non-significant variables can be safely excluded from the models (that is, none of the likelihood ratio results were significant at the .05 level).  

Table 3. Significant Results of Logistic Regression Estimates of Regional Variation in Territorial Force     

t1                           t2                                 t3                           t4        

Center                                  -1.54***             -1.60***                   -1.92***                 
                       (.45)                    (.49)                          (.59)
Central America                                                                               -2.17**                                     
                                                                                   (.83)                     
South America                                                                                   1.80*                    5.01**
                                                                                   (.84)                   (1.80)
West Africa                                                     -2.31*                                                     3.26*
                                                (1.19)                                                    (1.39)
Central Africa                                                  -2.80**                                                    
                                                (1.15)  
East Africa                                                                  

Southern Africa                                                                                                            -2.95**
                                                                                 (1.17)                     
Northern Africa                                                 
                                                  
Middle East                                                                                                                    3.47**
                                                                                                             (1.36)
East Asia                                                                                             
                                                                                   
South Asia                                                                                                                      3.32*
                                                                                                             (1.39)
Southeast Asia                                                 -1.61*
                                                  (.69)
Eastern Europe                                                            -2.42**                                                            2.36**
                                                  (.93)                                                    (1.40)
Constant                                  .33                      .60                           -.60                    -4.32***
                       (.75)                    (.60)                          (.66)                   (1.31)
Chi-square                           19.60*                46.16***                  76.74***              15.56
Log-likelihood                    -92.21               -131.60                            -94.69             -43.63
% Correctly Predicted          66.67                  73.56                        85.06                    78.95

* p < .05; ** p < .01; *** p < .001.  Two-tailed tests.  Standard errors in parentheses.

1 Ns reported in different time periods (t1-t4) mirror the total N=s for the given periods, adding a previously explained neutral control group.  In addition, likelihood ratio tests were run for each of the above models (t1-t4), all of which indicated that non-significant variables can be safely excluded from the models (that is, none of the likelihood ratio results were significant at the .05 level).

for East Asia and South America.  But it also highlights statistically significant results absent from Table 1.  In specific time periods, actors in West Africa, the Middle East, and South Asia have been significantly more prone to use belligerent force than the neutral control group.  While such findings are intriguing, they are not highly statistically significant and they do not indicate a consistent trend toward belligerent force in these regions.  The light that such results shed on the propensity of actors in these regions to use belligerent force is consequently limited.  Table 3 similarly supports the evidence from Table 1 that the Center, Central America, Southern Africa, and Eastern Europe have been at times significantly less likely to use force over territory than the neutral reference category.  Table 3 also seems to highlight one notable finding that Table 1 conceals.  It appears that territorial force increased significantly in many peripheral subsystems in t4, the post-Cold War era.  Five subsystems report positive, statistically significant coefficients.  It must be emphasized, however, that the logistic regression model for t4 in Table 3 does not fit well, as the model chi-square underscores.  These findings must be treated with caution.     

  

An Alternative Measure:  The Volume of Belligerent Force

The models in Tables 1-3 estimate the proclivity of actors in different regions to use belligerent rather than non-belligerent force and territorial rather than non-territorial force.  This measure has limitations.  Most notably, a subsystem might experience a large number of belligerent and non-belligerent interventions simultaneously.  Hostile acts could cause a surge in non-belligerent interventions, to shore up allies= borders, to protect minorities, to evacuate nationals, or to provide safe passage for refugees.  Non-belligerent interventions could likewise spark belligerent attacks.  The ratio of belligerent to non-belligerent interventions might be low in these circumstances even if disputes over belligerent issues regularly turn violent in the region.  It would thus be wise to examine the total volume of belligerent force used in regional subsystems in addition to this ratio.
Table 4 presents regional frequency counts for the past five decades.  Regions are listed from those with the least belligerent interventions per regional actor to those with the most.  The results correspond to those presented in Table 1.   The Center, Southern Africa, Central Africa, and Central America are among the regions where actors have been least likely to deploy hostile military forces into neighboring countries.  East Asia is among the regions where belligerent force has been used most often.
An examination of intervention frequencies does produce one notable result absent from Tables 1-3.  Over the past five decades, actors in Southeast Asia and the Middle East have used belligerent force more often than their counterparts in East Asia.  This outcome is masked in the graphs and the logistic regression models presented in this article because non-belligerent interventions were prevalent in the former regions.  In

                        Table 4. The Volume of Belligerent Force Used in Regional Subsystems, 1946-1996

                   Belligerent Uses of Force                 Belligerent Uses of Force
                        Subsystem                           Per Actor                                            Total N

                        Center                                      .08                                           2                     
                        Southern Africa                       .26                                           4
                        Central Africa                          .27                                           3
                        Northern Africa                       .40                                           2         
                        Central America                       .41                                           9
                        West Africa                             .50                                           7
                        South America                         .66                                           8         
                        Eastern Europe                        .73                                           19
                        East Africa                               1.16                                         7
                        South Asia                               1.20                                         16
                        East Asia                                  1.70                                         11
                        Southeast Asia                         2.10                                         21                   
                        Middle East                              2.67                                         19

other words, force has been used for a multitude of reasons in these areas, whereas it was deployed primarily for hostile purposes in East Asia.  If future research finds that the high levels of non-belligerent force recorded in Southeast Asia and the Middle East were largely in response to the threats posed and the humanitarian emergencies created by belligerent violence, these locales must also be considered among the least stable of the past fifty years.  

 

                                                                   Conclusions

A regional approach provides a great deal more nuance, and is more faithful to the empirical evidence, than a framework that distinguishes center from periphery.  The center-periphery dichotomy conceals the fact that some regional subsystems in the periphery are less prone to belligerent force than others, and some of these appear to be becoming even less so over time.  These areas may be slowly evolving past the types of bitter conflicts that result in recurrent interstate force.  Central America and Southern Africa are prominent examples, for force is rarely used over territorial issues in these regions, and belligerent uses of force have been uncommon in Southern Africa.  At least one regional subsystem seems to be headed in the opposite direction.  Actors employ belligerent force much more frequently than non-belligerent force in East Asia, and they have recorded a comparatively high number of belligerent interventions per actor over the past fifty years.  This subsystem seems likely to be a tension-filled pocket within the current international system, with lingering animosities over basic issues like territory and considerable potential for future conflict.
Such variance across regional subsystems is the most important finding of this study.  Tracing regional differences provides insight not only into the present stability of the world=s subsystems, but also their prospects for the future.  What=s more, doing so demonstrates that while umbrella concepts like the periphery and the zone of turmoil capture an important kernel of truth concerning conflict processes across the globe, they also have inherent liabilities.  The use of such blanket concepts limits our ability to explain and predict significant regional variation.
Further research is needed to provide a more detailed map of the use of force across regions.  At a minimum, such studies should control for a range of variables that have the potential to influence decisions to intervene.  States= military capabilities, alliances, economic strength, and  regime type might be among the variables considered.  Regional characteristics could also be included, such as the concentration of power in the region, the average age of the states in the region, and the total number of alliances there.  Future studies might analyze the military force that non-state actors, such as rebel and mercenary forces, use across borders as well.  Much remains to be done.  Nonetheless, this article provides a first cut at understanding patterns of military force across regions.  It demonstrates that significant regional differences do exist, and at times are marked.
Moreover, an appreciation of regional variance may grow increasingly important for the study of conflict in the first decades of the new century.  The propensity to use force over belligerent issues and over territory seems to have declined over the past five decades in the international system as a whole.  Given the fact that overall levels of interventionary force have remained steady over that same period (Pickering, 1999), this finding provides at least tentative grounds for optimism.  If belligerent and territorial force continue to wane in some of the world=s more stable regional subsystems, the probability that new, embryonic zones of peace might emerge necessarily increases.  Other considerations will certainly be important in the process of forging regional stability.  But, if present trends persist, a handful of peripheral subsystems may well continue along paths that diverge from our standard conception of the zone of turmoil.  Differences in the conflictual behavior of regional subsystems will thus become even more glaring.  In such an international context, regional analysis will be not only important for a thorough understanding of global conflict patterns, it will be essential.

 

Appendix A

States have been assigned to regional subsystems primarily on a subjective basis as developed in Pearson and Bauman (1989), Pearson, Baumann, and Pickering (1994), and Pickering and Thompson (1998).  A few states not found in the Pearson and Baumann (1993-94) data collection’s codebook have been added.  The subsystemic assignments are more likely to be overly inclusive rather than overly exclusive.  In other words, several of the subsystems could be further subdivided into smaller regional systems.

Center- Australia, Austria, Belgium, Canada, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Japan, Luxembourg, Netherlands, New Zealand, Norway, Portugal, Spain, Sweden, Switzerland, Turkey, U.K., and U.S.
Central America - Cuba, Haiti, Dominican Republic, Jamaica, Trinidad/Tobago, Barbados, Mexico, Guatemala, Honduras, Nicaragua, Panama, El Salvador, Costa Rica, Bahamas, Dominica, Grenada, St. Lucia, St. Vincent, Antigua, St. Christopher (Kitts)-Nevis, Anguilla, and Belize
South America - Columbia, Venezuela, Guyana, Ecuador, Peru, Brazil, Bolivia, Chile, Paraguay, Argentina, Uruguay, and Suriname
West Africa - Gambia, Mali, Senegal, Benin, Mauritania, Niger, Ivory Coast, Guinea, Burkina-Fasso (Upper Volta), Liberia, Sierra Leone, Ghana, Togo, Nigeria, Guinea-Bissau, and Cape Verde
Central Africa - Cameroon, Gabon, Central African Republic, Chad, Congo, Democratic Republic of Congo (Zaire), Burundi, Rwanda, Equatorial Guinea, Sao Tome, and Principe
East Africa - Uganda, Kenya, Tanzania, Somalia, Ethiopia, Djibouti
Southern Africa - Zambia, Malawi, South Africa, Lesotho, Botswana, Madagascar/Malagasy Republic, Angola, Mozambique, Zimbabwe, Swaziland, Comoros, Mauritius, Seychelles, Reunion
Northern Africa - Morocco, Algeria, Tunisia, Libya, Sudan
Middle East - Iran, Turkey, Iraq, Egypt, Syria, Lebanon, Jordan, Israel, Saudi Arabia, Yemen Arab Republic, Yemen (PDR), Kuwait, Abu Dhabi, Bahrain, Qatar, United Arab Emirates, Oman
East Asia - China, Mongolia, Japan, Taiwan, North Korea, South Korea, Tibet
South Asia - Afghanistan, India, Junagadh, Kashmir, Hyderabad, Sikkim, Pakistan, Myanmar (Burma), Sri Lanka, Maldive Islands, Nepal, Bangladesh, Bhutan
Southeast Asia - Thailand, Cambodia, Laos, North Vietnam, South Vietnam, Malaysia,
Singapore, Philippines, Indonesia, Brunei
Oceania - Papua New Guinea, Vanuatu, Solomon Islands, Fiji, Marshall Islands, Micronesia, Western Samoa.  Note: this subsystem is not included in this article’s estimates because of its small intervention N.
Eastern Europe - Croatia, Bosnia-Herzegovina, Moldova, Ukraine, Belarus, Hungary, Poland, Czech Republic, Slovakia, Slovenia, Albania, Bulgaria, Romania, Estonia, Latvia, Lithuania, Russia, Georgia, Armenia, Azerbaijan , Turkmenistan, Tadzhikistan, Kirgizia, Uzbekistan, Kazakhstan

 

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