Wars Without End: Competitive Intervention, Escalation Control, and Protracted Conflict

Wars Without End: Competitive Intervention, Escalation Control, and Protracted Conflict, by Noel Anderson (New York: Oxford University Press, 2025), 304 pp., cloth $99, eBook $88.99.

The post–Cold War, unipolar era was a boom time for the empirical study of civil war, spawning large literatures on matters such as conflict mediation and UN peacekeeping. Scholarship deemphasized the study of one-sided and competitive foreign interventions in civil wars—also known as “proxy war”—because the rate of such interventions was comparatively low. Wars Without End helps reopen the investigation of competing foreign military aid during internal civil war, a topic that is likely to be particularly germane as the international system becomes multipolar and international cooperation declines.

Civil wars with competing foreign intervenors tend to be especially lengthy. Wars Without End confirms this pattern with new data on foreign intervention in civil wars. Rather than limiting the focus to foreign troops, Noel Anderson tracks all forms of one-sided, military-related intervention: troops, weapons, financial aid, access to territory and infrastructure, war matériel, logistics, intelligence, assistance with recruitment or weapons procurement, and so on. This expansive inventory of foreign intervention reveals how profoundly internationalized the phenomenon of civil war has long been. Between 1946 and 2009, while a minority of civil conflicts involved sending foreign troops, approximately three-fourths were targeted by some form of foreign military assistance (pp. 58–69). During the Cold War, about 40 percent of civil wars featured competitive interventions, including 11 percent that featured simultaneous military aid from the United States and USSR. After 1990, only 20 percent of internal wars had competing foreign adversaries aiding the parties. In both eras, competitive interventions were associated with longer civil wars.

Anderson offers a novel argument for why that pattern exists, focusing on the strategic calculus of the foreign adversaries assisting opposing actors in a civil conflict. These countries must balance their interest in the outcome of the conflict against the “risks inherent in competitive intervention: conflict spirals, action-reaction dynamics and direct confrontation” (p. 6). A common compromise is to provide just enough support to one’s ally to hold off defeat but not enough to deliver a decisive military advantage. As a result, fighting is exceptionally protracted.

Wars Without End uses detailed case studies to trace the relationship between escalation risk and foreign intervention strategies in the Angolan Civil War (1975–1991) and the war in Afghanistan (1979–1992). Both case studies draw on declassified government records, primary and secondary materials, as well as the author’s interviews with military leaders and diplomats. Anderson offers a remarkably granular look at the military implications of foreign intervention. Case studies of protracted war often detail frustrated diplomatic efforts and the high politics of aid allocation. Anderson puts more focus on how foreign actors make tactical decisions that balance the desire to help the local ally and the risk of escalation. These decisions include the geography of troop movements, rules of engagement, and target selection. Anderson reviews the strategic calculus around these matters for both the minor and major powers in each conflict: South Africa, Cuba, the USSR, and the United States during the Angolan Civil War; and, in the chapter on Afghanistan, decision-making by Pakistan, the United States, and the USSR. I plan to assign these chapters as stand-alone readings about the war-fighting side of civil war for my undergraduate classes as a complement to the more readily available accounts of diplomacy and political contestation.

On the other hand, the theory-testing function of these chapters is somewhat hamstrung by the case selection. The key argument in the book is that the risk of escalation between foreign adversaries disciplines their intervention strategies. However, in both case narratives, as well as the shadow case of the Syrian Civil War, the escalation risk is ultimately related to the tensions between Washington, D.C., and Moscow. Put another way, the escalation risks when major military powers with atomic weapons intervene in a civil war may not generalize to other competing interventions. A richer version of the theory in Wars Without End would treat the chances of escalation due to competitive intervention as a variable rather than a static constraint, with higher and lower risks of escalation, in terms of both likelihood of a conflict spiral and costs in the event of such a confrontation. Escalation risk would depend on both the capabilities of the foreign intervenors and the strategic significance of the civil war for each of them. That risk should, in turn, predict intervenors’ decision-making and the duration of the war.

The quantitative results in Wars Without End also raise some questions about the logic of the argument, suggesting the need for a more complex version of the theory. Anderson’s reasoning implies that each foreign intervenor could propel their local ally to victory if there were no rival outside actors whose presence restrains them from providing decisive advantages. The implication is that—all else equal—the shortest civil wars should be those with one relatively unconstrained foreign intervenor. Instead, the quantitative results imply that civil wars without any foreign intervention end the earliest (p. 96). The difference in expected duration of wars without external supporters compared to wars with one-sided interventions is not statistically significant. However, even that non-result raises doubts about whether foreign actors could produce rapid conflict termination but for the presence of a rival country.

A more technical but related point is that Wars Without End does not fully deal with the possibility that wars that would probably be long under any circumstances also attract more foreign interventions. Anderson discusses endogeneity under the heading of reverse causality, checking for the possibility that foreign countries intervene in wars that have already lasted a very long time (pp. 103–104). However, the thornier endogeneity problem is the possibility that hard-to-measure properties of conflict generate both intractability and an incentive for outside intervention early in the war. In my view, it is probably not possible to fully eliminate this problem in a statistical setting. However, because Anderson does not raise this endogeneity problem, there is also no discussion in the qualitative sections about how intervention decisions did or did not relate to factors that might have contributed to a long war regardless of foreign choices.

Nonetheless, Wars Without End helps to move the study of civil conflict toward the problem of one-sided and rival interventions, which are only likely to become more important in the postunipolar world. Anderson’s monograph should be read by all conflict studies scholars and is a worthy addition to a graduate syllabus relating to internal war or international rivalry. As I have noted, I also plan to use the book’s case studies when teaching undergraduates. The third chapter in Wars Without End will be especially useful, as it clearly reviews debates over long-term trends in levels of warfare worldwide and shows patterns in military interventions in civil war by era. This chapter also presents Anderson’s novel, expanded descriptive data on various forms of intervention across time and would be a useful model for graduate students developing a data collection strategy.

—Bethany Lacina

Bethany Lacina is an associate professor of political science at the University of Rochester. Her research interests are in ethnic conflict, migration, and political violence.