Conflict, Terrorism, Peacekeeping, and International Institutions

Chapter Opening

On a January morning in 1992, the United Nations Security Council gathered for the first time at the level of heads of state and government. The Cold War, which for more than four decades had frozen the Security Council into paralysis through the competing vetoes of the United States and the Soviet Union, had just ended. Delegates spoke hopefully of a "new world order," a phrase that captured a widespread belief that with the ideological struggle between capitalism and communism resolved, the underlying machinery of international cooperation — the United Nations, international law, collective security — might finally function as its founders had intended in 1945. Secretary-General Boutros Boutros-Ghali was asked to prepare a report on how the United Nations might strengthen its capacity for preventive diplomacy, peacemaking, and peacekeeping. The resulting document, "An Agenda for Peace," radiated optimism about what international institutions could accomplish now that superpower rivalry no longer blocked them at every turn.

That optimism did not survive the decade. Within three years, the world watched as the United Nations proved unable to prevent the genocide of roughly eight hundred thousand Rwandans in 1994 or the massacre of more than eight thousand Bosnian Muslim men and boys at Srebrenica in 1995, in each case despite the presence of UN peacekeepers on the ground. Civil wars tore apart Somalia, Liberia, Sierra Leone, Yugoslavia, and the Democratic Republic of the Congo. A new and different kind of violence — transnational terrorism carried out by non-state networks rather than by armies of recognized states — culminated in the attacks of September 11, 2001, which killed nearly three thousand people and reshaped the security priorities of nearly every government on earth. By the early twenty-first century, the confident language of a "new world order" had given way to more sober, more contested, and more urgent questions: How should the international community respond when a government turns violently against its own population? What obligations, if any, do states have to protect people beyond their borders? Can international law hold powerful leaders accountable for atrocities? And can peacekeeping, built originally to monitor ceasefires between states, be adapted to the far more dangerous task of protecting civilians inside collapsing states and stopping violence driven by networks that recognize no borders and no laws?

This chapter examines conflict and international security in the decades after the Cold War. It studies civil wars and state collapse, the resurgence of ethnic and nationalist violence, the rise of transnational terrorism, the evolution of humanitarian intervention and the doctrine known as the Responsibility to Protect, the transformation of United Nations peacekeeping from ceasefire monitoring into complex multidimensional operations, the development of international law and international courts capable of prosecuting genocide and war crimes, the global refugee crisis produced by decades of conflict, and the immense and often unresolved difficulty of building durable peace after violence ends.

The regions at the center of this chapter are genuinely global. The former Yugoslavia in southeastern Europe experienced the most destructive European conflict since 1945, including the first legally established genocide verdict in Europe since the Nuremberg trials. Rwanda, in Africa's Great Lakes region, endured one of the fastest and most efficient mass killings in modern history, followed by conflicts in the neighboring Democratic Republic of the Congo that killed millions more through violence, disease, and displacement over the following decade — sometimes called "Africa's World War." Afghanistan and Iraq became the sites of the two longest wars in United States history, wars launched in response to terrorism but that evolved into complicated exercises in state-building and counterinsurgency. Syria's civil war, beginning in 2011, produced the largest refugee crisis since World War II and drew in regional and global powers whose competing interests made peace extraordinarily difficult to achieve. Sierra Leone, Liberia, Somalia, Sudan and South Sudan, Sri Lanka, Colombia, and many other states experienced civil wars whose causes, dynamics, and resolutions varied enormously but which together defined this era as one shaped less by wars between great powers than by violence within and across fragile states.

What changed in this period was the character of organized violence itself. The great interstate wars that historians of the twentieth century studied — World War I, World War II, even many Cold War proxy conflicts — were fought primarily between the organized militaries of recognized states. After 1991, the overwhelming majority of armed conflicts were civil wars: fighting within states, often between government forces and rebel groups, frequently along ethnic, religious, or regional lines, and frequently complicated by the involvement of neighboring states, diaspora communities, international arms suppliers, and eventually transnational terrorist networks that exploited weak or collapsed state authority. What continued, painfully, was the vulnerability of civilians. In earlier centuries, and even through much of the twentieth century, military casualties often exceeded civilian casualties in armed conflict. In the civil wars and irregular conflicts that dominated the post–Cold War period, civilians were frequently not incidental casualties but deliberate targets — driven from their homes, subjected to ethnic cleansing, used as human shields, or killed in campaigns of terror designed to break the will of entire communities.

Historians and international relations scholars studying this period draw on an unusually wide range of evidence: United Nations reports and Security Council records, the transcripts and judgments of international criminal tribunals, human rights investigations by organizations such as Human Rights Watch and Amnesty International, satellite imagery documenting mass graves and destroyed villages, refugee testimony collected by aid organizations, declassified government cables and intelligence assessments, and the growing body of academic research on civil war, terrorism, and peacebuilding that emerged as these became central subjects of political science and international relations. Because many of the events in this chapter occurred within living memory, and because some remain legally and politically contested, historians must exercise particular care in weighing evidence, distinguishing verified fact from propaganda, and acknowledging where the historical record remains incomplete or disputed.

This chapter connects directly to patterns studied throughout this textbook: the collapse of empires and the difficulties of decolonization examined in earlier chapters; the ideological struggles of the Cold War; the human rights movements that grew after 1945; and the deep, unresolved tensions between state sovereignty and the protection of human beings that have run through world history since the modern state system first took shape in seventeenth-century Europe. It also sets the stage for the final chapter of this textbook, which asks what patterns from the whole of world history — migration, state formation, exchange, conflict, and the search for order — help us understand the world of the twenty-first century.

Learning Objectives

Guiding World-History Questions

Historical Context

To understand conflict after the Cold War, students must first understand what the Cold War's end actually changed and what it left unchanged. For more than four decades after 1945, the rivalry between the United States and the Soviet Union shaped nearly every regional conflict on earth. Civil wars in Angola, Nicaragua, Afghanistan, and dozens of other states were fueled, armed, and often prolonged by superpower competition, as each side supplied weapons, funding, and military advisers to opposing factions in proxy struggles that served larger ideological and strategic purposes. The United Nations Security Council, whose five permanent members hold veto power, was frequently paralyzed, as the United States and the Soviet Union blocked resolutions that threatened their respective allies or interests. Genuine collective security — the vision the UN's founders had articulated in 1945, in which the international community would act together against aggression — rarely functioned as intended.

The collapse of the Soviet Union in 1991, examined in earlier chapters, removed the ideological and strategic framework that had shaped conflict for two generations. In some respects this created new opportunities: the Security Council, no longer paralyzed by superpower rivalry, authorized more peacekeeping operations in the five years after 1991 than in the previous four decades combined, and briefly it seemed that international cooperation on security matters might genuinely flourish. But the end of the Cold War also removed constraints. Regimes that had received support from Washington or Moscow for strategic reasons, regardless of their internal legitimacy, sometimes collapsed once that support disappeared, leaving political vacuums that armed factions rushed to fill. Ethnic, religious, and regional tensions that had been suppressed or managed under Cold War–era authoritarian rule or federal structures — as in Yugoslavia and parts of the former Soviet Union — resurfaced violently once central authority weakened. And in parts of Africa, Asia, and the Middle East, weak postcolonial states whose borders had been drawn by European empires with little regard for ethnic, linguistic, or religious geography faced new pressures without the stabilizing, if often self-interested, patronage of Cold War superpowers.

The 1990s therefore produced a wave of conflicts that differed in important ways from the interstate wars and Cold War proxy conflicts of the preceding decades. Political scientists began speaking of "new wars" or "intrastate conflict" to describe fighting that occurred primarily within state borders, often involved irregular armed groups rather than professional militaries, frequently targeted civilian populations as a strategic objective rather than an unfortunate side effect, and was often financed not by superpower patrons but by control over natural resources such as diamonds, timber, or drugs, by diaspora remittances, or by criminal networks. Somalia's central government collapsed in 1991 amid clan-based fighting, producing decades of instability. Yugoslavia, a multiethnic federation that had held together under the authoritarian rule of Josip Broz Tito and, after his death, a weakening federal structure, fragmented into war beginning in 1991, with the most severe violence occurring in Bosnia and Herzegovina between 1992 and 1995. Rwanda's 1994 genocide grew out of decades of colonial-era ethnic categorization, political manipulation, and unresolved civil conflict. Sierra Leone and Liberia experienced brutal wars fueled substantially by control over diamond mining. The Democratic Republic of the Congo, following the 1994 Rwandan genocide and the subsequent overthrow of its own long-ruling dictator, became the site of a conflict so large, so multi-sided, and so costly in human life — estimates of deaths from war-related violence, disease, and starvation between 1998 and the mid-2000s range as high as five million — that it is sometimes called Africa's Great War or Africa's World War.

At the same time, a different kind of security threat was taking shape: transnational terrorism carried out by non-state networks operating across multiple countries, often justified by radical religious or political ideology, and frequently unconnected to any single state's foreign policy in a conventional sense. Organizations such as al-Qaeda, formed in the late 1980s partly out of networks that had fought against Soviet forces in Afghanistan, carried out increasingly ambitious attacks through the 1990s before the September 11, 2001, attacks on the United States transformed global security policy. The "war on terror" that followed reshaped alliances, produced two of the longest wars in modern history in Afghanistan and Iraq, and raised difficult and enduring questions about the balance between security and civil liberties, about the legality of military detention and interrogation practices, and about whether military force could ever fully defeat a decentralized ideological movement.

Running alongside these conflicts was a parallel and often frustrated effort to strengthen international institutions capable of preventing, managing, and punishing mass violence: the expansion and redesign of UN peacekeeping; the creation of ad hoc international criminal tribunals for the former Yugoslavia and Rwanda; the eventual establishment of a permanent International Criminal Court in 2002; and the adoption in 2005 of the Responsibility to Protect doctrine, which asserted that the international community bears a responsibility to protect populations from genocide, war crimes, ethnic cleansing, and crimes against humanity when their own governments fail or refuse to do so. This chapter traces both halves of this story: the recurring, often catastrophic violence of the post–Cold War world, and the uneven, contested, sometimes inspiring and sometimes tragically inadequate international effort to prevent and respond to it.

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Regional Orientation

This chapter is genuinely global in scope, and students should locate its major regions carefully. Southeastern Europe (the former Yugoslavia — Bosnia and Herzegovina, Croatia, Serbia, Kosovo) saw the collapse of a multiethnic socialist federation into war along ethnic and religious lines, drawing NATO and the UN into direct military and administrative roles in Europe for the first time since 1945. Central Africa's Great Lakes region (Rwanda, Burundi, the Democratic Republic of the Congo) experienced genocide and a subsequent regional war involving as many as nine African states, rooted partly in colonial-era ethnic categorization and partly in struggles over land, political power, and mineral resources. West Africa (Sierra Leone, Liberia) saw wars fueled by control over diamonds and by the regional spillover of armed groups and child soldiers. Southwest AsiaSouth Asia (Sri Lanka's long civil war) and the Horn of Africa (Somalia's prolonged state collapse) provide further examples of protracted intrastate conflict. Each of these regions connects to the others through shared international institutions — above all the United Nations Security Council, which authorizes peacekeeping and, in principle, collective responses to mass atrocity everywhere on earth — and through the global structures of arms trafficking, diaspora financing, humanitarian aid, and media coverage that link distant conflicts into a single, interconnected story of post–Cold War violence and the international response to it.

Major People, Groups, Places, and Polities

Core Vocabulary Preview

Conflict After the Cold War

When the Cold War ended, many observers hoped that the removal of superpower rivalry would reduce global conflict. In one narrow sense, they were correct: the large-scale proxy wars in which the United States and Soviet Union armed opposing factions in places like Angola and Nicaragua wound down. But the total number of armed conflicts did not decline in the way many had hoped, and in the first years after 1991, the number of active civil wars around the world actually rose. What changed was the character of conflict rather than its frequency. Interstate war — conflict between the organized militaries of recognized states — became comparatively rare, though it did not disappear, as the Gulf War of 1991 and later the Russia-Georgia war of 2008 and the Russian invasion of Ukraine beginning in 2014 and escalating in 2022 demonstrated. Overwhelmingly, however, the wars of the post–Cold War decades were intrastate conflicts: civil wars fought within the borders of a single state, even when neighboring states, diaspora communities, or international actors became deeply involved.

Scholars who study this shift point to several contributing factors. First, the withdrawal of superpower patronage after 1991 destabilized regimes and rebel movements alike that had depended on Cold War-era support, sometimes triggering collapse and sometimes intensifying competition to fill the resulting vacuum. Second, weak postcolonial states — many of which had been held together more by authoritarian force, foreign patronage, or the personal authority of a single ruler than by strong, broadly legitimate institutions — proved especially vulnerable once those external props were removed. Third, economic globalization created new ways for armed groups to finance themselves independent of state sponsors, through control of valuable natural resources such as diamonds, timber, oil, or narcotics, or through diaspora remittances sent by expatriate communities abroad. Fourth, small arms proliferation — the vast stockpiles of assault rifles and other weapons built up during the Cold War and often left unsecured after conflicts ended — made it easier for irregular armed groups, including those with only a few hundred or a few thousand fighters, to wage sustained campaigns of violence.

These new wars differed from earlier conflicts in another crucial respect: the proportion of civilian casualties. Estimates vary and are contested by scholars, but many studies of twentieth-century conflict suggest that civilian deaths, as a share of total conflict deaths, rose substantially over the course of the century, and that in many post–Cold War civil wars, civilians made up the overwhelming majority of those killed, wounded, or displaced. This was not always incidental. In conflicts driven by ethnic or religious division, civilians were frequently targeted deliberately — through massacres, sexual violence used as a weapon of war, forced displacement, and the deliberate destruction of homes, farms, and infrastructure — as a strategic means of achieving territorial or political goals. This targeting of civilian populations as a central rather than incidental feature of warfare is one of the defining and most disturbing characteristics of the conflicts examined in this chapter.

Civil Wars and State Collapse

State collapse — the breakdown of a central government's ability to maintain order, provide services, and exercise authority over its territory — is both a cause and a consequence of civil war. Somalia offers one of the starkest examples. After the overthrow of longtime dictator Siad Barre in January 1991, no successor government was able to establish control over the country. Rival clan-based militias fought for territory and resources, and for more than two decades Somalia had no effective central government, becoming the textbook case of a "failed state." The absence of governance had cascading effects: humanitarian catastrophe, including a severe famine in 1992 that prompted a U.S.-led humanitarian and later military intervention that ended disastrously with the 1993 "Black Hawk Down" battle in Mogadishu; the growth of piracy off Somalia's coast in the 2000s, which threatened international shipping and drew naval responses from multiple countries; and the eventual rise of the militant group al-Shabaab, which exploited the absence of state authority to build a insurgent base.

Yugoslavia's collapse followed a different trajectory but illustrates similar dynamics. The Socialist Federal Republic of Yugoslavia, established after World War II under Josip Broz Tito, held together six republics and multiple ethnic and religious communities — Serbs, Croats, Bosniaks (Bosnian Muslims), Slovenes, Macedonians, Montenegrins, and ethnic Albanians in Kosovo — through a combination of authoritarian one-party rule, a carefully balanced federal structure, and Tito's own considerable personal authority. After Tito's death in 1980, the federal system weakened, and by the late 1980s, nationalist politicians, most prominently Slobodan Milošević in Serbia, began mobilizing ethnic nationalism as a political strategy, often invoking historical grievances — including memories of World War II-era atrocities between the region's ethnic communities — to build support. When Slovenia and Croatia declared independence in 1991, war broke out, followed by a far more destructive war in Bosnia and Herzegovina beginning in 1992, where Bosnian Serb forces, with support from Serbia, pursued a campaign of ethnic cleansing against Bosniak and Croat populations that included the systematic use of concentration camps, mass killing, and sexual violence, culminating in the July 1995 Srebrenica massacre, in which more than eight thousand Bosniak men and boys were killed by Bosnian Serb forces in a UN-declared "safe area" that peacekeepers were unable to protect.

The Democratic Republic of the Congo (formerly Zaire) illustrates how state collapse can produce conflict on a continental scale. Weakened by decades of corrupt and predatory rule under Mobutu Sese Seko, Zaire's fragile state structures collapsed amid the regional spillover of the 1994 Rwandan genocide, as Hutu militia forces and refugees fled across the border into eastern Zaire, and Rwanda's new government pursued them militarily. Mobutu was overthrown in 1997, and a subsequent conflict beginning in 1998 — sometimes called the Second Congo War — eventually drew in the armed forces of at least eight other African states, competing over territory, political influence, and access to the DRC's vast mineral wealth, including gold, diamonds, and coltan (used in electronics manufacturing worldwide). Estimates of total deaths from the conflict and its consequences, including violence, disease, and malnutrition, range from roughly two to five million people between 1998 and the mid-2000s, making it among the deadliest conflicts anywhere in the world since 1945, though it received comparatively little sustained international media attention or diplomatic engagement relative to its scale.

Ethnic Conflict and Nationalism

A common but misleading explanation for conflicts in Yugoslavia, Rwanda, and elsewhere holds that they resulted from "ancient ethnic hatreds" that had simmered for centuries and finally exploded once authoritarian control was removed. Historians and social scientists have largely rejected this explanation as both inaccurate and dangerous, because it implies that such violence is inevitable and beyond the reach of political choice or international response. The evidence instead points overwhelmingly toward a different explanation: ethnic conflict in the modern era is typically produced through deliberate political mobilization by leaders who invoke, exaggerate, and sometimes fabricate historical grievances in order to build political power, often in moments of economic crisis or political transition when other bases of legitimacy have weakened.

Rwanda illustrates this dynamic with particular clarity. The distinction between Hutu and Tutsi identities in Rwanda was not, before European colonization, a rigid ethnic or racial division; it more closely resembled a fluid social and economic distinction that could shift with circumstances such as cattle ownership. Belgian colonial administrators, drawing on pseudo-scientific racial theories current in early twentieth-century Europe, rigidified this distinction into a fixed racial category, issued identity cards recording "ethnicity," and favored the Tutsi minority in administration and education for much of the colonial period before reversing course and favoring the Hutu majority in the years before independence. This colonial legacy of rigid, state-recorded ethnic categorization provided the infrastructure — quite literally, in the form of identity documents — that later political leaders would exploit. In the early 1990s, facing civil war with a Tutsi-led rebel movement and economic crisis, extremist Hutu politicians and media, most infamously the radio station RTLM, engaged in a sustained campaign of dehumanizing propaganda against Tutsis, describing them as "cockroaches" and enemies of the nation, laying the ideological groundwork for the genocide that followed the assassination of Rwanda's president in April 1994.

Yugoslavia's ethnic violence followed a similar pattern of political mobilization rather than spontaneous ancient hatred. Serbs, Croats, and Bosniaks had lived together, often peacefully and with high rates of intermarriage, for generations under Tito's Yugoslavia. Nationalist politicians in the late 1980s and early 1990s revived and amplified memories of World War II-era atrocities — including massacres committed by fascist Croatian Ustaše forces against Serbs, and by various factions against one another — selectively and often exaggerating them for contemporary political purposes, framing the coming conflict as a defensive necessity rather than a war of choice. Understanding ethnic conflict as the product of political choice and mobilization, rather than inevitable historical destiny, is essential both for accurate historical analysis and for the practical work of conflict prevention, since it suggests that such violence can, at least in principle, be anticipated, resisted, and prevented through political and institutional means.

Terrorism and Global Security

Terrorism — the use of violence against civilians or non-combatants to create fear and achieve political, religious, or ideological objectives — is not a new phenomenon in world history; anarchist bombings in the late nineteenth century, nationalist assassinations before World War I, and numerous other historical episodes qualify as terrorism by most definitions. What changed in the late twentieth and early twenty-first centuries was the emergence of transnational terrorist networks capable of planning and executing attacks across multiple countries, financed and organized independently of any single state sponsor, and animated by ideologies — most prominently a radical, violent interpretation of Islamist politics, though far from the only ideological source of terrorism in this period — that explicitly rejected the framework of the state system altogether.

Al-Qaeda, formed by Osama bin Laden and others in the late 1980s partly from networks of fighters who had participated in the war against Soviet occupation of Afghanistan during the 1980s, carried out a series of escalating attacks through the 1990s, including the 1998 bombings of U.S. embassies in Kenya and Tanzania and the 2000 attack on the USS Cole in Yemen, before the September 11, 2001, attacks on the World Trade Center and the Pentagon killed nearly three thousand people and transformed global security policy virtually overnight. The United States, invoking NATO's collective defense clause for the first time in the alliance's history, led an invasion of Afghanistan in October 2001 to remove the Taliban government that had sheltered al-Qaeda, beginning what became the longest war in American history, lasting until the U.S. withdrawal and the Taliban's return to power in 2021. The broader "war on terror" that followed reshaped intelligence-sharing, airport and border security, banking and financial regulation aimed at cutting off terrorist financing, and — controversially — the legal treatment of detained terrorism suspects, including practices such as indefinite detention at Guantánamo Bay and "enhanced interrogation techniques" that human rights organizations and many legal scholars characterized as torture.

The 2003 U.S.-led invasion of Iraq, justified partly by since-discredited claims that Saddam Hussein's government possessed weapons of mass destruction, was not originally framed as a counterterrorism operation, but it produced a prolonged insurgency and sectarian civil war that created conditions in which extremist groups flourished, including al-Qaeda in Iraq, whose successor organization eventually became the Islamic State, or ISIS. Exploiting the chaos of the Syrian civil war after 2011 and continued instability in Iraq, ISIS seized large territories across both countries in 2014, declared a "caliphate," and combined battlefield territorial control with sophisticated propaganda, including graphic videos of executions distributed globally through social media, to attract recruits from dozens of countries. An international coalition eventually drove ISIS from its territorial holdings by 2019, but the organization persisted as a decentralized insurgent and terrorist network, and its ideology inspired attacks carried out by individuals and small cells with no direct organizational connection, a pattern security analysts termed "lone wolf" or inspired terrorism, which proved extremely difficult for traditional counterterrorism methods to prevent.

Humanitarian Intervention

The catastrophic failures of the international community to prevent genocide in Rwanda and mass killing in Bosnia during the 1990s prompted intense debate about whether and when outside powers should intervene militarily inside a sovereign state to stop mass atrocities — a practice generally termed humanitarian intervention. Proponents argued that state sovereignty could not be an absolute shield behind which governments committed genocide or ethnic cleansing against their own populations, and that the international community bore a moral obligation to act when it had the capacity to prevent mass death. Critics — including many governments in the developing world that had experienced European colonial domination and remained wary of great-power intervention justified by humanitarian language — warned that "humanitarian intervention" could become a pretext for powerful states to violate the sovereignty of weaker ones for self-interested reasons, and that inconsistent application (intervening in some crises while ignoring others of comparable severity) revealed that geopolitical interest, not humanitarian principle, often actually determined which crises received a military response.

NATO's 1999 intervention in Kosovo, undertaken without explicit UN Security Council authorization after Russia and China indicated they would veto such authorization, became a pivotal and controversial case. NATO bombed Serbian forces for seventy-eight days to halt a campaign of ethnic cleansing against Kosovo's ethnic Albanian population, ultimately forcing a Serbian withdrawal and establishing international administration over Kosovo, which declared independence in 2008. Supporters described Kosovo as a justified humanitarian action; critics, including Russia, pointed to the lack of Security Council authorization as a dangerous precedent for unilateral military action outside international law.

Partly in response to these unresolved debates, the International Commission on Intervention and State Sovereignty proposed in 2001 a new framework called the Responsibility to Protect, formally adopted by the United Nations at the 2005 World Summit. R2P held that sovereignty entails responsibility: states have a primary obligation to protect their own populations from genocide, war crimes, ethnic cleansing, and crimes against humanity, and where a state manifestly fails to do so — whether through inability or unwillingness, including when a state is itself the perpetrator — the international community has a responsibility to take collective action, through the UN Security Council, up to and including military intervention as a last resort. R2P represented a significant, if incomplete and contested, shift in international norms regarding sovereignty, though its practical application remained inconsistent: it was invoked to authorize NATO's 2011 intervention in Libya, which many governments later criticized as having exceeded its narrow civilian-protection mandate and contributed to Libya's subsequent state collapse, while it was never successfully invoked to authorize meaningful international military action to stop the far larger death toll of the Syrian civil war after 2011, largely because Russia and China used their Security Council vetoes to block such action.

Peacekeeping and the United Nations

United Nations peacekeeping was not explicitly provided for in the UN Charter; it developed pragmatically, beginning with early Cold War-era operations that primarily involved monitoring ceasefires between states with the consent of the parties involved, using lightly armed troops authorized to use force only in self-defense — an approach sometimes called "traditional" or "first-generation" peacekeeping. The end of the Cold War transformed both the volume and the character of peacekeeping. Freed from superpower gridlock, the Security Council authorized far more operations, and these operations increasingly took on far more ambitious "multidimensional" mandates: not merely monitoring ceasefires between state armies, but protecting civilians within ongoing civil wars, disarming and demobilizing combatants, organizing and monitoring elections, supporting the reconstruction of police and judicial systems, and assisting the return of refugees and displaced persons.

This expansion produced both notable successes and devastating failures. Peacekeeping operations helped stabilize transitions and end conflicts in countries such as Namibia, Mozambique, El Salvador, and Cambodia during the 1990s. But peacekeeping's most searing failures also occurred during this decade, and both centered on the same fundamental problem: UN peacekeepers, operating under mandates and rules of engagement designed for traditional ceasefire monitoring rather than for the protection of civilians in active conflict, proved unable to stop mass killing even when peacekeepers were present in significant numbers. In Rwanda, the small UN peacekeeping force present when the genocide began in April 1994 was actually reduced by the Security Council in the crucial early weeks of the killing, after ten Belgian peacekeepers were killed and troop-contributing countries, above all Belgium, pressed for withdrawal rather than reinforcement; the force commander, Canadian general Roméo Dallaire, had earlier warned UN headquarters of planned violence and requested authorization to seize weapons caches, a request that was denied. In Bosnia, Dutch peacekeepers stationed in the UN-declared "safe area" of Srebrenica in July 1995 were unable to prevent Bosnian Serb forces under General Ratko Mladić from separating men and boys from women and children and executing more than eight thousand of them over several days, one of the worst episodes of mass killing in Europe since World War II.

These failures prompted extensive institutional reflection. The UN commissioned independent inquiries into both Rwanda and Srebrenica that produced unusually candid acknowledgments of institutional failure. The 2000 Brahimi Report, commissioned by Secretary-General Kofi Annan (who had himself headed the UN's peacekeeping department during the Rwandan genocide), recommended more robust mandates, clearer rules of engagement authorizing peacekeepers to use force to protect civilians, better resourcing, and more realistic assessments of what peacekeeping operations could actually accomplish before they were authorized. Subsequent operations, including large deployments in the Democratic Republic of the Congo, Sudan/Darfur, South Sudan, and Mali, generally adopted more explicit civilian protection mandates, though troop shortages, inadequate equipment, ambiguous chains of command among multinational forces, and continuing political constraints from troop-contributing and Security Council member states meant that the gap between mandate and capacity remained a persistent challenge throughout the following decades.

International Law and War Crimes

The post–Cold War period saw the most significant expansion of international criminal justice since the Nuremberg and Tokyo tribunals following World War II. The UN Security Council established the International Criminal Tribunal for the former Yugoslavia (ICTY) in 1993, while the Bosnian war was still ongoing, and the International Criminal Tribunal for Rwanda (ICTR) in 1994, in the genocide's immediate aftermath. These ad hoc tribunals prosecuted individuals — not states — for genocide, war crimes, and crimes against humanity, establishing important legal precedents. The ICTR's 1998 judgment against former Rwandan mayor Jean-Paul Akayesu was the first conviction for genocide by an international tribunal and the first to recognize that rape and sexual violence could constitute acts of genocide when used to destroy a targeted group. The ICTY's judgments regarding Srebrenica, including the conviction of Bosnian Serb general Radovan Karadžić and Ratko Mladić decades after the massacre, formally established in international law that the killings at Srebrenica constituted genocide — a legal conclusion that Serbian nationalist politics continued to dispute long after the court's judgment.

Building on the experience of these ad hoc tribunals, the international community negotiated the Rome Statute, establishing a permanent International Criminal Court (ICC), which came into force in 2002 and began operating from The Hague in the Netherlands. Unlike the ICTY and ICTR, which were created for specific conflicts and had defined end dates, the ICC was designed as a permanent institution with potential jurisdiction over genocide, war crimes, crimes against humanity, and the crime of aggression committed after 2002 by nationals of member states or on the territory of member states, or referred to it by the UN Security Council. The ICC represented a landmark development in the long historical effort to hold individuals, including heads of state, personally accountable under international law rather than allowing sovereign immunity to shield perpetrators of mass atrocity.

The ICC's record, however, illustrates the continuing limits of international law when it collides with the realities of state power. Several major states — including the United States, Russia, China, and India — never joined the court, limiting its jurisdiction and its enforcement capacity, since the ICC has no independent police force and depends on member states to arrest and surrender indicted individuals. Sitting heads of state indicted by the court, including Sudan's Omar al-Bashir (indicted in 2009 for genocide and war crimes in Darfur) and, more recently, Russian president Vladimir Putin (indicted in 2023 in connection with the war in Ukraine), have generally been able to avoid arrest by remaining within, or traveling only to, states unwilling to enforce ICC warrants. Critics, particularly from African states, have also pointed out that the large majority of the ICC's early cases involved African defendants, raising questions about whether international justice has been applied even-handedly across regions and levels of power — a criticism the court has taken steps to address by opening investigations into situations beyond Africa, including in Afghanistan, Palestine, and Ukraine.

Refugees and Displacement

The conflicts examined throughout this chapter produced displacement on a scale unmatched since the aftermath of World War II. By the early 2020s, the UN High Commissioner for Refugees estimated that more than one hundred million people worldwide had been forcibly displaced from their homes by conflict, violence, and persecution — a figure that includes refugees who have crossed international borders, internally displaced persons who remain within their own country's borders but cannot return home, and asylum seekers awaiting determination of their status. Syria's civil war alone displaced more than half the country's pre-war population, with over six million Syrians registered as refugees, primarily in neighboring Turkey, Lebanon, and Jordan, and millions more internally displaced within Syria itself. Conflicts in Afghanistan, South Sudan, the Democratic Republic of the Congo, Myanmar (whose Rohingya Muslim minority faced a campaign of violence and expulsion that the UN and other bodies characterized as ethnic cleansing beginning in 2017), and Venezuela (whose economic and political collapse, though not primarily a conflict in the conventional sense, produced one of the largest displacement crises in the Western Hemisphere) each contributed further to this global total.

The legal and institutional framework for refugee protection dates to the 1951 Refugee Convention, drafted in the aftermath of World War II and the displacement it caused, which defines a refugee as someone with a well-founded fear of persecution based on race, religion, nationality, political opinion, or membership in a particular social group, and establishes the principle of non-refoulement — the obligation not to return refugees to a country where they would face persecution. This framework, designed for a mid-twentieth-century world of comparatively contained, state-based conflicts, has come under increasing strain in the post–Cold War era of civil war, state collapse, and climate-linked displacement, which produces categories of forced migration — including displacement driven by generalized violence and state collapse rather than individualized persecution, and displacement driven by environmental factors — that the original convention did not fully anticipate.

Host countries, frequently poorer neighboring states rather than wealthy nations, have borne a disproportionate share of the burden of hosting refugees: Turkey has hosted the largest number of registered refugees of any country in the world for much of the past decade, primarily Syrians, while Pakistan and Iran have hosted millions of Afghan refugees across four decades of conflict, and Uganda has become one of Africa's largest refugee-hosting countries, primarily for people fleeing South Sudan and the DRC. This pattern — in which comparatively poor states neighboring conflict zones host the overwhelming majority of the world's refugees, while wealthier and more distant states host a much smaller proportion despite often intense domestic political controversy over migration — has become one of the more consequential and often overlooked features of the global refugee system, with significant implications for economic development, social services, and political stability in host countries themselves.

The Challenges of Peacebuilding

Ending active fighting is only the first, and often the easiest, step toward durable peace. Peacebuilding — the longer-term process of addressing the underlying causes of conflict, rebuilding institutions, fostering reconciliation, and creating conditions in which violence does not recur — has proven to be exceptionally difficult, and scholarly research on civil wars has found that a substantial proportion of conflicts that end through negotiated settlement rather than decisive military victory relapse into renewed violence within a decade. Understanding why peace is so difficult to sustain is essential to evaluating the post–Cold War record of conflict resolution.

Several recurring obstacles appear across many post-conflict societies. Security sector reform — disarming and demobilizing former combatants, reintegrating them into civilian life, and building trustworthy police and military institutions — often proves enormously difficult, particularly where former combatants have few alternative economic opportunities and where security forces themselves were implicated in wartime atrocities. Transitional justice — the effort to address wartime crimes through mechanisms such as trials, truth commissions, reparations, or memorialization — must navigate a difficult balance between accountability, which victims and human rights advocates often insist upon as essential to genuine reconciliation, and the political necessity, in many negotiated settlements, of offering amnesty or power-sharing arrangements to perpetrators in order to secure their cooperation with a peace agreement in the first place. South Africa's Truth and Reconciliation Commission, established after the end of apartheid and examined in an earlier chapter, offered one influential model emphasizing truth-telling and conditional amnesty over prosecution; Rwanda's post-genocide government instead pursued both formal international prosecution through the ICTR and a massive program of community-based traditional justice courts, called gacaca, to process the enormous number of genocide-related cases that formal courts could never have handled alone.

Economic reconstruction presents further difficulties: war-torn economies typically require enormous investment in rebuilding infrastructure, restarting agriculture and commerce, and creating employment, particularly for demobilized young fighters who might otherwise be drawn back toward violence; yet post-conflict states frequently lack functioning tax systems, face high levels of corruption, and depend heavily on international aid that can create dependency or be captured by political elites rather than reaching the broader population. Political power-sharing arrangements, often central to peace agreements that end civil wars by guaranteeing formerly warring factions a share of government positions, can stabilize immediate post-conflict transitions but sometimes entrench the very ethnic or factional divisions that produced conflict in the first place, as critics have argued occurred in Bosnia's Dayton-era constitutional structure, which many analysts view as having stabilized peace while simultaneously freezing ethnic division into the country's permanent political architecture.

Chapter Review and Conflict Analysis Checkpoint

This chapter has examined the transformed landscape of conflict after the Cold War: the dominance of civil war and state collapse over interstate war; the way ethnic conflict is produced through political mobilization rather than ancient hatred; the rise of transnational terrorism and the global security response it provoked; the contested doctrine of humanitarian intervention and the Responsibility to Protect; the evolution and repeated failures and reforms of UN peacekeeping; the development of international courts capable of prosecuting genocide and war crimes; the unprecedented scale of global forced displacement; and the immense and often unresolved difficulty of building peace that lasts. Before proceeding, students should be able to explain how each of these elements connects to the others within a single, interconnected post–Cold War security landscape.

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