The short brutal conflict in Kosovo, beginning late February 1998 and extending through mid-June 1999, sparked a sustained debate between Western governments and their societies about the purpose and methods of collective military action. The war brought with it an intensification of Belgrade's effort to cleanse non-Serbian populations from the Federal Republic of Yugoslavia (FRY). NATO's campaign in response to these horrors was the first large-scale military action by the alliance in its history.

The U.S. State Department estimates that 11,000 Kosovar Albanians were killed over the course of the conflict. The Serbian government claims that the Serbian military suffered 5,000 casualties during the conflict, and approximately 1,500 Serb civilians were killed during the NATO aerial bombardment. The Serbian assault in Kosovo resulted in one of the largest population deportations during the twentieth century.

The war in Kosovo triggered a complex and passionate debate about the application of international humanitarian law (IHL) to an internal conflict in which gross human rights abuses are committed by a nation-state against its own citizens. The competing claims of IHL and the laws of nations reached a crucial juncture in the fall of 1998; ongoing massacres of civilians in Kosovo provided the political and moral imperative to take action, but no sound legal authority could be extracted from the UN Security Council or from NATO founding documents.

International humanitarian law imposes an obligation on states to deal with grave breaches of the law, but whether this obligation extends to authorizing the use of armed force against another state is a wholly different question. This tension was operationally resolved by NATO's decision in March 1999 to bombard the FRY in order to uphold the international regime of human rights and international law. The FRY and some of its traditional allies challenged this hostile act as a violation of international law against a sovereign state. However, the NATO action must also be interpreted in light of the decision of the International Criminal Tribunal for the former Yugoslavia (ICTY), in May 1999, to indict President Slobodan Milosevic as a war criminal, the first time a sitting head of state has been so charged.

The conflict between Serbs and Albanians escalated over the course of the 1990's. The 1995 Dayton Peace Accords failed to address the serious unresolved grievances that had been festering in Kosovo. The lack of an effective framework for dealing with the dispute in Kosovo led to widespread impatience within the Kosovar Albanian community and fueled the mobilization of the Kosovo Liberation Army (KLA). In late January 1998 the KLA intensified its attacks against Serbian military police in western Kosovo. Serbian reprisals in early February killed the alleged instigator of these attacks as well as over 80 members of his extended clan.

Throughout the spring of 1998 hostilities between the KLA and the Serbian forces continued unabated in Kosovo. By the summer Milosevic's forces began to wage increasingly indiscriminate assaults against villages in central Kosovo, driving a total of 300-400,000 people into the hills and blocking virtually all efforts to provide humanitarian assistance. By this time, the West was frustrated in its effort to stop the cycle of violence. The question of legal protection for civilians remained relevant in that as a party to both Additional Protocols as well as to the Geneva Conventions, Yugoslavia could have been held to the more stringent protection provisions of Protocol II, as well as Article 3 common to the Geneva Conventions.

In September, word began to filter out that Serbian forces had committed massacres of civilians. Public outrage over the atrocities intensified the debate about whether intervention should be taken on IHL grounds. No consensus existed for intervention in a "non-permissive" environment, so the West finally settled on having Milosevic accede to a cease-fire and security arrangement independently monitored by the Organization for Security and Cooperation in Europe (OSCE). In mid-October, in return for Milosevic's agreement to reduce his forces in Kosovo and permit humanitarian access, the West demanded that the KLA to cease hostile action.

During November and December the agreement held, allowing independent verifiers to move into Kosovo and humanitarian aid agencies to access displaced civilian populations. At the same time, however, it was evident that Serbian forces were being redeployed in Kosovo in direct violation of the agreement. The Serbian redeployment brought with it the return to open hostilities in the countryside. At that time, an event occurred that significantly changed the direction of the conflict. On January 15, 1999, a massacre of 45 people occurred in Racak, a small village in south central Kosovo. William Walker, the head of the OSCE mission in Kosovo, visited the site the next day and called the killings "without doubt a crime against humanity." This allegation was supported by the release of U.S. recordings of Serbian police cell phone conversations, which indicated this attack was deliberately launched against civilians thought to be collaborating with the KLA.

The gross violations allegedly committed by the Serbs — coupled with increasingly violent reprisals by the KLA — served as a catalyst for a final negotiating effort between the parties in Rambouillet, France. These contentious sessions ended with Yugoslav President Milosevic's rejection of the proposals negotiated in Rambouillet. The NATO bombing campaign began on March 24. At the outset, the air attacks were directed at tactical targets in Kosovo and strategic targets in Serbia.

In order to evade Serbian anti-aircraft defenses, NATO pilots made their bombing runs at high altitudes (usually at or above 15,000 feet) and at night. Poor weather and evasive Serbian ground tactics hampered the sorties. On at least three occasions during raids over Kosovo, NATO forces inadvertently hit civilians in convoys or KLA prisoners in buildings. Targets in Serbia included industrial sites, bridges, railheads, and urban electrical grids. In an effort to stem the war propaganda broadcast from Belgrade, NATO decided to destroy one of its most controversial targets: the headquarters of Serbian Radio and Television.

NATO justified its action as an attempt to protect the civilian population of Kosovo from ongoing human rights abuses; to stabilize regional security in Europe; and to maintain NATO's credibility. As Serb forces, unchecked by the bombing, accelerated ethnic cleansing within Kosovo, the first and possibly the second rationale for NATO bombing collapsed. The question of civilian protection turned into one of preventing genocide. What was actually going on inside Kosovo at that time was difficult to verify; reports from those who had fled suggested that hundreds, if not thousands, of people might have been killed. The memory of Srebrenica was alive in the public consciousness and the daily NATO and U.S. government briefings delivered warnings of mass killings.

The number of civilians killed during the Serbian rampages remains a subject of considerable dispute. There is less argument about the numbers forced into flight. In the week after the onset of NATO bombing, hundreds of thousands of people crossed into Albania, Macedonia and Montenegro. By mid-April an estimated 800,000 Kosovars had been expelled, and another 500,000 were thought to be internally displaced.

On May 27, 1999, the ICTY indicted President Milosevic for war crimes and crimes against humanity. This indictment, explicitly limited to events after January 1, 1999, charged Milosevic and four others in the Serbian command structure with systematic or widespread deportation, murder, and persecution of Kosovar civilians on political, racial, and religious grounds. Specific mention was made of the killings in Racak and in six other villages, amounting to 340 named Albanian victims. The impact of indicting a sitting head of state for war crimes and crimes against humanity was initially obscured by a debate about its timing. Would Milosevic be less likely to settle given his new legal jeopardy? Was the unsealing of the indictment politically motivated by NATO or the U.S.? While the impact of the indictment on Milosevic's thinking relative to other factors is a subject of speculation, within only days of the indictment Milosevic appeared more willing to engage diplomatically with Russian and Finnish intermediaries. A cease-fire was agreed to on June 10, 1999.

Among the lingering legal controversies from this war are whether body counts were inflated for political purposes and if NATO should be charged for despoiling the Balkan environment or for war crimes in its attacks on non-military targets in Serbia. The first of these has effectively been settled by reviewing the record. Most estimates of deaths during the spring of 1999 were in the 10,000 range. Investigators continue their work in Kosovo. Based on forensic investigation of ethnic cleansing conducted in Bosnia, it is estimated that ultimately there will still be several thousand unaccounted for and presumed murdered in Kosovo, according to the Organization for Security and Cooperation in Europe.

On the basis of presently available information, determining whether the Serbs committed genocide is unclear. Genocide is a narrowly-defined crime that is distinct from the types of atrocities often committed against civilian populations in war. In April and May of 1999, however, to have raised a concern about Milosevic's genocidal intent and capacity was arguably well grounded. At that time, much was known about his past propensity, and little could be ascertained about the circumstances in Kosovo, except that 800,000 people fled and the remaining civilian population faced the virtually unopposed ground forces of the Serbian army. The law of genocide calls upon nation-states to act to prevent genocide. No precedent exists and no measurement has been developed to assist a watching world in knowing with certainty when genocide is about to occur. In this post-cold war period of heightened attention to IHL and the crime of genocide, there is a compelling need to attach usable, empirically based definitions to threshold guidelines for international action.

With regard to possible environment damage, in the fall of 1999 two different groups of United Nations environmental experts reviewed the effects of the NATO bombing campaign. They determined that it is difficult to distinguish the potential impact of the NATO bombing from earlier, communist-era environmental damage. At the same time, the potential effects of depleted uranium and of unexploded ordnance, including NATO cluster bombs, remain subjects of heated debate. In terms of NATO war crimes, the Office of the Prosecutor for the ICTY indicated in December 1999 that there is no formal inquiry into the actions of NATO during the conflict in Kosovo. The fact that the case was brought and heard at all, however, has significant implications for the potential jurisdiction and reach of the future International Criminal Court in ruling on the legality of great powers' conduct in future conflicts.

The debate over IHL infused the public and official controversies surrounding the war in Kosovo to an extent unprecedented in other conflicts of the 1990's. In its midst emerges one clear legal and political legacy: for the first time collective international action was mobilized to confront forcibly a profound challenge to humanitarian norms. Whether that action itself was legal in the absence of UN Security Council resolution is an important but subsidiary question. As the framework for improving legal justifications and practice evolves, however, we should not lose sight of the lesson: the community of nations — in the case of Kosovo — could find a common purpose in preventing genocide.

Jennifer Leaning is Senior Research Fellow, Harvard Center for Population and Development Studies and Director of the Center's Program on Human Security and Complex Humanitarian Emergencies. Board certified in internal medicine and emergency medicine, Dr. Leaning is Assistant Professor of medicine at Harvard Medical School, an attending physician in the Emergency Department of Brigham and Women's Hospital, and teaches disaster management and response to humanitarian crises at the Harvard School of Public Health.

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