MANY GOVERNMENTS around the world identify stopping and stemming "ethnic and religious hatreds" as a major foreign-policy priority. Quite simply, in the words of the 2006 U.S. National Security Strategy, such "conflicts do not stay isolated for long and often spread or devolve into humanitarian tragedy or anarchy." Yet, ethnic conflicts do not simply appear out of thin air. They can be traced primarily to the decisions of political leaders. The spread of ethnic conflict is not automatic either. For existing ethnic conflicts to move beyond their original borders, the relevant actors-ethnic communities, states and other private-interest groups-need to make a choice. If they choose to expand the conflict, they need three things: the motive, the means and the opportunity.

Ethnic conflict spreads in two principal patterns: diffusion and escalation. Diffusion means that the existence of one ethnic conflict leads to the occurrence of others, either elsewhere in the same state or in other, often neighboring, states. Escalation, on the other hand, describes a situation in which more actors become involved in the same conflict as belligerent parties.

The traditional patterns of the spread of ethnic conflict exhibit close links between escalation and diffusion and typically occur when ethnic groups mobilized on the basis of some combination of greed, grievance or security concerns confront each other, the states in which they live or both. Ethnic groups, states or a combination of both can drive these conflicts. They are predominantly played out on a regional level (e.g., in the western Balkans, in the Greater Middle East) and involve not only the immediate neighbors of an ongoing conflict, but they also draw in regional and great powers.

The literature on ethnic conflict is full of different theories about its ultimate causes. There are three common explanations. One focuses on cost-benefit calculations or "greed": conflicts happen when profit is to be made. A second sees social, political, economic and other grievances as powerful explanations as well. Here, the argument is that conflict happens when people are dissatisfied with their status compared to other groups in society or feel that their status is threatened. So conflict can become a strategy either to change or defend the status quo. Finally, the third considers the so-called security dilemma as central among the causes of ethnic conflict. When people perceive their survival as individuals and members of a group is at risk, they seek to avert this threat by using violence preemptively against those who they consider to be the main source of the threat.

In most ethnic conflicts, participants are motivated by a mix of profit, status and security considerations. This is important for the diffusion of ethnic conflict because one conflict can only spread within or beyond a given country if people elsewhere are receptive to it. They must be motivated to pursue their interests by means of conflict, and they need the means and opportunity to do so.

THE CONFLICT in Sudan is primarily driven by ethnic groups. In the Darfur crisis, the government, through the Arab janjaweed militias, is targeting local Darfurian communities. The government claims their attacks originally came in response to the western rebel groups-the Sudanese Liberation Army and the Justice and Equality Movement-challenging President Omar al-Bashir, but many label the conflict genocide.

When the thirty-year civil war between north and south was approaching a negotiated settlement in the first years of the twenty-first century, the rebel groups elsewhere in the country wanted a greater share in the emerging new political and economic bargain as well. Their motive was improved political and economic status. Neighboring Chad, in particular, was motivated to play a role in the conflict by its keen interest in weakening the regime in Khartoum; the Chadian government alleged that Sudan was the main sponsor of antigovernment rebels in Chad.

The Sudanese government had the means to carry out repression in Darfur in the form of the janjaweed militias. The western rebel groups, in the meantime, benefited from easy access to bases in Chad and received arms and equipment from there (as well as from Eritrea).

Opportunities presented by ongoing negotiations and international involvement in Sudan combined with motivation and means to make conflict possible. Having learned the "lesson" that violence pays by seeing it bring the government to the negotiating table, ready to make concessions, the movements in Darfur launched attacks against government forces. They even had a Plan B (for some of them it may even have been Plan A): if the government did not respond with concessions but with increased repression, then surely a humanitarian emergency would result. The international community would take sides with the local movements, shifting the balance of power away from the government.

As this case shows, the causes of the spread of ethnic conflict come not just from the local or state levels. This becomes more clear when one considers why neither Plan A nor Plan B of the Darfur movements worked. The Sudanese government was in a very favorable position that allowed it to pursue a policy of ruthless repression in Darfur. Equally as important as the existence of the means and motive was the international-opportunity structure. Initially, the African Union and UN mediators in the north-south conflict hesitated to become involved for fear of jeopardizing a settlement. This allowed Khartoum to negotiate a separate deal with the south and exclude Darfur from the so-called Comprehensive Peace Agreement of 2005. It was the close economic partnership between Sudan and China that protected the former from any hard-hitting action by the UN Security Council, despite the gravity of the human-rights violations in Darfur.

As the situation in Darfur worsened with mass killings and refugee flows, there was a second wave of diffusion, this time spreading directly into Chad and leading to an almost-successful coup against the government there. Military operations conducted by regular Chadian forces in Sudan in response in early 2008 also illustrate that escalation and diffusion are often closely linked.

Kosovo is another illustrative example of the complexity of the spread of ethnic conflict. At the extreme end, not just a case of diffusion or escalation, but simply the precedent set by Kosovo's independence is seen as a potential cause of conflict proliferation. Here, the initial conflict was also driven by ethnic antagonisms: Serbs and Albanians equally sought full control of Kosovo.

Control of means played an important part in halting the spread of the conflict. For ten years, successive preventive deployment missions-by the UN and later NATO and the EU-made sure that Macedonia was not dragged into the violence that engulfed the western Balkans throughout the 1990s. On the other hand, not having curbed the proliferation of small arms from Albania to Kosovo was one of the major facilitating factors that made the rise of the Albanian Kosovo Liberation Army (KLA) possible from the mid-1990s onward. The rise of the KLA-which called for the independence of Kosovo and was considered a terrorist group with links to organized crime, including by many in the West-was also aided significantly by a "tax" collected among diaspora Albanians in Western Europe and the United States.

The NATO-led intervention in 1999, motivated primarily by concerns over the grave violation of human rights in Kosovo, was an early example of escalation. At that time, Russia, too, resisted Western policy but eventually accepted Kosovo's UN-led administration under Security Council Resolution 1244. Almost ten years on, Russian resistance to Kosovo's unilateral declaration of independence and its recognition is far more uncompromising. While Russia has neither the means nor the opportunity to engage the West militarily, it may well contribute to the diffusion of the Kosovo conflict, albeit in a different way.

Kosovo is presented by Russia, and others, as an opportunity, a dangerous precedent for the creation of new states by unilateral acts of those seeking to realize their claims to self-determination through secession. That Kosovo has been able to pursue this path and find relatively widespread international recognition, it is argued, will inspire secessionist movements elsewhere to follow the Kosovo example. That it is unlikely this line of reasoning will have any practical merit-after all, even Russia has so far refused to recognize separatist regions across the former Soviet Union-is less important.

The very fact that self-determination movements elsewhere can now cite the case of Kosovo is likely to make the settlement of some of these conflicts more difficult because movements elsewhere will refer to Kosovo as a precedent based not only on the view of Russia, but also strengthened by similar pronouncements from China, Spain, Romania, Slovakia and Greece to name but a few. This has already affected, and will continue to affect, places as diverse as Sri Lanka, Indonesia, the Philippines, Thailand, India, China, Somaliland, South Sudan, Ethiopia and Tanzania.

Yet, diffusion is also likely much closer to Kosovo: Macedonia, with its roughly 25 percent ethnic Albanian population right across the border from Kosovo, and Bosnia and Herzegovina, with its highly discontent Serbian community, are perhaps the most likely early "victims" of diffusion. On the other hand, escalation in the sense of external belligerents entering the frame is unlikely. A strong NATO and EU military presence on the ground across the Balkan region will prevent or at least swiftly contain local violence. The still-feasible promise of closer relations with, and eventual membership in, the European Union is also likely to calm any desire for major trouble.