What is the difference between genocide and ethnic cleansing?

Someone has just asked me what is the difference between genocide and ethnic cleansing. Good question. I found it difficult to articulate a short answer. The following excerpt from Encyclopaedia Britannica says some critics see little difference between genocide and ethnic cleansing:

Ethnic cleansing is the attempt to create ethnically homogeneous geographic areas through the deportation or forcible displacement of persons belonging to particular ethnic groups. Ethnic cleansing sometimes involves the removal of all physical vestiges of the targeted group through the destruction of monuments, cemeteries, and houses of worship.

The term ethnic cleansing, a literal translation of the Serbo-Croatian phrase etnicko ciscenje, was widely employed in the 1990s (though the term first appeared earlier) to describe the brutal treatment of various civilian groups in the conflicts that erupted upon the disintegration of the Federal Republic of Yugoslavia. These groups included Bosniacs (Bosnian Muslims) in Bosnia and Herzegovina, Serbs in the Krajina region of Croatia, and ethnic Albanians and later Serbs in the Serbian province of Kosovo. The term also has been attached to the treatment by Indonesian militants of the people of East Timor, many of whom were killed or forced to abandon their homes after citizens there voted in favour of independence in 1999, and to the plight of Chechens who fled Grozny and other areas of Chechnya following Russian military operations against Chechen separatists during the 1990s.

According to a report issued by the United Nations (UN) secretary-general, the frequent occurrence of ethnic cleansing in the 1990s was attributable to the nature of contemporary armed conflicts, in which civilian casualties and the destruction of civilian infrastructure are not simply by-products of war, but the consequence of the deliberate targeting of non-combatants... [I]n many conflicts, belligerents target civilians in order to expel or eradicate segments of the population, or for the purpose of hastening military surrender.

Ethnic cleansing as a concept has generated considerable controversy. Some critics see little difference between it and genocide. Defenders, however, argue that ethnic cleansing and genocide can be distinguished by the intent of the perpetrator: whereas the primary goal of genocide is the destruction of an ethnic, racial, or religious group, the main purpose of ethnic cleansing is the establishment of ethnically homogeneous lands, which may be achieved by any of a number of methods including genocide.

Another major controversy concerns the question of whether or not ethnic cleansing originated in the 20th century. Some scholars have pointed to the forced resettlement of millions of people by the Assyrians in the 9th and 7th centuries BC as perhaps the first cases of ethnic cleansing. Among other examples cited are the mass execution of Danes by the English in 1002, attempts by the Czechs to rid their territories of Germans in the Middle Ages, the expulsion of Jews from Spain in the 15th century, and the forced displacement of Native Americans by white settlers in North America in the 18th and 19th centuries.

Others argue that ethnic cleansing, unlike earlier acts of forced resettlement, is the result of certain uniquely 20th-century developments, such as the rise of powerful nation-states fueled by nationalist and pseudoscientific racist ideologies in conjunction with the spread of advanced technology and communications. Examples of ethnic cleansing understood in this sense include the Armenian massacres by the Turks in 1915-16, the Nazi Holocaust of European Jews in the 1930s and '40s, the expulsion of Germans from Polish and Czechoslovak territory after World War II, the Soviet Union's deportation of certain ethnic minorities from the Caucasus and Crimea during the 1940s, and the forced migrations and mass killings in the former Yugoslavia and Rwanda in the 1990s. In many of these campaigns, women were targeted for particularly brutal treatment - including systematic rape and enslavement - in part because they were viewed by perpetrators as the "carriers," biologically and culturally, of the next generation of their nations. Because many men in victimized populations left their families and communities to join resistance groups once violence began, women and children were often defenseless.

The precise legal definition of ethnic cleansing has been the subject of intense scrutiny within various international bodies, including the UN, the two ad hoc international tribunals created in the 1990s to prosecute violations of international humanitarian law in the former Yugoslavia and in Rwanda (the International Criminal Tribunal for the Former Yugoslavia [ICTY] and the International Criminal Tribunal for Rwanda [ICTR], respectively), and the International Criminal Court (ICC), which began sittings in 2002.

In 1992, in reference to the hostilities in Yugoslavia, the UN General Assembly declared ethnic cleansing to be "a form of genocide," and in the following year the Security Council, citing widespread and flagrant violations of international humanitarian law within the territory of the former Yugoslavia, established a tribunal to investigate allegations of war crimes and crimes against humanity, including ethnic cleansing. In its examination of the capture of the town of Kozarac by Bosnian Serbs, the ICTY described the ethnic cleansing that took place there as the process of rounding up and driving "out of the area on foot the entire non-Serb population." In a subsequent case, the tribunal recognized similarities between acts of genocide and ethnic cleansing, noting that both involve the targeting of individuals because of their membership in an ethnic group. The significant difference between the two remains, however: whereas ethnic cleansing aims to force the flight of a particular group, genocide targets the group for physical destruction.

The establishment of the ICC reinforced the links between ethnic cleansing and other offenses such as genocide, crimes against humanity, and war crimes. In its finalized text on the elements of the crimes in the court's jurisdiction, the Preparatory Commission for the International Criminal Court made clear that ethnic cleansing could constitute all three offenses within the ICC's jurisdiction. Genocide, for example, was defined as an act that may include the systematic expulsion of individuals from their homes; the threat of force or coercion to effect the transfer of a targeted group of persons was recognized as an element of crimes against humanity; and the "unlawful deportation and transfer," as well as the displacement, of civilians were recognized as elements of war crimes.

Despite continuing controversies over its definition, the concept of ethnic cleansing has become firmly anchored within international law. It remains to be seen how mechanisms to prevent and deal with ethnic cleansing will develop and be implemented.