Introduction

Treks of the expelled and the fleeing are among the defining national and transnational lieu de mémoire in European history of the 20^th century. Flight and expulsion have also occurred in previous centuries,¹ but now took on gigantic proportions. 50 to 80 million Europeans presumably left their homes involuntarily. These estimates are difficult to verify. Statistical recording of human tragedies is full of gaps, contradictions and possible double counts. Also, the terms used for quantification are defined differently from country to country. In addition, national discourses, the struggle for the "politically correct" choice of words, and the shaping of the national, and transnational "memorial cultures" remain in full swing.² The collapse of the communist systems in 1989, the opening up of until then inaccessible archival materials, and the historiographical processing of previously taboo topics has resulted in an intensive debate on forced migrations. Although conducted in a very controversial manner, this discussion increasingly permits recognition of remarkable rapprochements across national boundaries. The following will exclusively discuss migrations enforced by 1. Command (force), 2. Violence, 3. Threats of violence, or 4. Fear of violence (revenge), with fluid transitions between the categories, to the extent that they were ethnically or nationally motivated. Flight due to socioeconomic or political motives, the evacuation or flight of parts of the population from the scenes of war and the deportation of prisoners of war have not been included if the ethnic/national affiliation of the affected did not play a causative or a clearly causative role (which cannot always be resolved beyond any doubt in specific cases). This paper does not discuss the deportation and murder of the Jews because the Holocaust is a separate topic.

Forced migrations in the meaning of this paper are the core of what has been summarized since the start of the war in Bosnia in 1992 under the term "ethnic cleansing".³ Ethnic cleansing is not a trivializing term for genocide but includes a broad spectrum of measures of which some – such as human rights violations, war crimes and genocide – are punishable, but others – e.g. an obligatory population exchange among states – are not. Ethnic cleansing includes those measures initiated and performed, encouraged or tolerated by a modern state or para-state and its agents that aim to remove a population that is stigmatised due to its ethnicity as "threatening", "disloyal", "alien" and often even as "inferior", from a particular territory. These measures are deliberate (intentional) and systematic but can also be accompanied by unregulated actions ("wild" expulsions) that are the result of the course of a conflict (processual or "functional" forms of ethnic cleansing). Evacuation and flight in anticipation of ethnic cleansing also belongs to this context. The objective of ethnic cleansing is not primarily genocide but a territorial removal of the ethnically "alien" and "hostile" population group(s) to cause the territory of the state, the constitutive people and "the people's soil" to coincide. The engine of this type of forced migration is always excessive national and ethnic portrayals of the enemy. Usually national or ethnic minorities in states that strive for ethnic and national homogeneity are affected.⁴ Forced migrations occur especially where the "Us" group of actors considers itself to be a community of descent and parts of its actual or claimed territory are inhabited by population groups who do not belong to this "Us" group or titular nation. Security arguments (prevention of separatist movements or repulsion of irredentist ambitions of a neighbouring state) play as much a role in this as revenge for suffered injustice or the redistribution of assets, societal resources and opportunities.

The "modernity" of forced ethnic migrations

The dramatic increase of forced ethnic migrations in 20th century Europe, or their modernity, has four causes:

1. In previous centuries, the ethnic affiliation of persons only played a subordinate or no role for the mass of the population (likewise for the rulers), especially since the criteria for affiliation to a large group (language, religion, settlement area, shared past, descent or a combination of several criteria) were often unclear or contradictory. In the always thinly settled areas of Eastern Europe, many rulers and owners of large territories deliberately introduced outsiders from the Middle Ages through to the 19th century to improve their territories and often granted them privileges. Only during the course of forming nations and nation states in the 19th and 20th centuries, the accompanying processes of inclusion and exclusion, and the striving for "definiteness" did ethnicity come to play the outstanding role that was attributed to it in the 20th century at the latest. People who could not be unambiguously classified in ethnic/national terms or changed their self-designation – which was normal in previous centuries – now became a problem. The modern sciences (especially biology, physical anthropology, genetics, ethnography/ethnology) and the race theories, which had spread since the late 19th century, have pushed ahead the classification of people according to ethnicities, nations and races as well as "ethnic engineering".⁵ In the pre-modern period, entire population groups were affected by expulsion, forced resettlement or flight, but usually not due to their ethnicity (which was in any case difficult to define). Rather, the reasons were religious (e.g., Jews, Moriscos, Hutterites, Huguenots) or due to actual or presumed disloyalty toward the ruler or as part of a settlement policy.

2. The crisis and decay of the great multi-ethnic empires in Europe (Ottoman empire, Habsburg monarchy, Tsarist Russia and the German empire) initiated a series of state formations: The political map of large parts of Europe was rearranged with reference to the right of peoples to self-determination according to "nation state" and ethnographic criteria. If all border changes of the 20th century are entered into a map, it is immediately noticeable that an area in the middle of Europe – between Western Europe and the compact Russian settlement area – is more strongly characterized by major boundary shifts than all other parts of the continent. In territories with an ethnically mixed population or with a population that (still) has not developed an ethnic, let alone, a national awareness and, for example, defines itself according to religion/confession or region, the right of self-determination unfolded its "dark" – and often little noted – side. It caused politicians and their scientific "aids" (ethnographers, linguists, historians) to "hide" or let "disappear" the existence of an ethnically different or differentiated population in a particular territory. Ethnic incorporation (against the will of the affected), expulsion, motivation to flight and mass murder developed into important instruments when enforcing nationally homogeneous territories.

3. The wars characterizing Europe in the 20th century were wars of mass destruction. The concept of the "contained war of states", which was developed after the Thirty Year War, broke down in the 20th century even though the Hague Convention respecting the Laws and Customs on War and Land of 1907 entrenched the differentiation between combatants and civilians in international law. The concept of the people's war, which has been advancing since the French Revolution with "levée en masse", the ethnification of wars and, finally, the development of weapons of mass destruction promoted the transformation of "classical" warfare. The ethnification of the "people's war" resulted in not just understanding the opposing army as the party waging war but also the entire "alien" population.

4. The great dictatorships of 20th century Europe – National Socialism and Stalinism – have ruthlessly abused ethnic concepts to impose their rule by force and found many imitators. The power apparatus required for this purpose was also a product of modernism.

The discussion to this point has not only intended to state the reasons for the clustering of ethnically motivated forced migration in the 20th century, but also to provide primary evidence of those parts of Europe that were particularly affected by it. Although forced ethnic migration has occasionally occurred in other parts of the Continent (e.g. in Alsace, which was fought over by Germany and France after the First World War, during the Nazi occupation and after the Second World War), most ethnic cleansings have occurred in eastern Central Europe, in South-eastern Europe and Eastern Europe (including the Asian parts of Russia and the Soviet Union), in other words, on the soil of the former multi-ethnic empires.⁶ These areas experienced a specific form of nation and nation state formation. In France, nation formation occurred in the context of an established state and the existing state or political community constituted an important reference point of collective identity formation (state into nation). However, nation builders without a state of their own or a state that was still young and fragile needed to refer to other community-lending criteria (nation into state). "Volkstum", the concept of an imagined community based on common descent and "culture", was particularly popular.⁷ As a result, ethnicity became the constitutive element of nation state formation in the central and eastern part of the continent. "Das Volk wurde als ethnische Gemeinschaft begriffen. Auch der Begriff der 'Staatsangehörigkeit', der an sich ohne jede ethnische Dimension ist, erhielt eine Einfärbung in Richtung auf die 'Volkszugehörigkeit'."⁸ This new orientation was pregnant with consequences. Already in 1855 a vocal representative of German nationalism, Paul Anton de Lagarde (actually Bötticher, 1827–1891), declared:

Es ist zweifellos nicht statthaft, dass in irgendeiner Nation eine andere Nation bestehe; es ist zweifellos geboten, diejenigen welche ... jene Dekomposition befördert haben, zu beseitigen: Es ist das Recht jedes Volkes, selbst Herr auf seinem Gebiet zu sein, für sich zu leben, nicht für Fremde.⁹

The German nation was a remarkable product of such constructions. After the founding of the empire, it consisted of two components: The Reichsdeutsche ("Reich-Germans") within the empire and the Auslandsdeutsche ("German expatriates") outside. In the interwar period, the term Volksdeutsche ("ethnic Germans") established itself for Germans living in other countries, meaning those (groups of) persons who were considered German due to "blood" and descent even if their German national awareness was only in statu nascendi.¹⁰ Therefore, Volkstumsforschung ("ethnicity research") and folktales experienced an astonishing popularity in Germany and many other European countries.¹¹ Descent is an extremely rigid criterion for inclusion and exclusion since descent (as opposed to language, religion and identification with a political community) cannot be chosen or changed. A person is either one of "us" by descent or not one of "us" – tertium non datur. It is neither possible to enter the community of descent nor to leave it. However, since the presumed common descent from large groups that is projected far into the past cannot be proven or refuted (even the Ariernachweis ["certificate of Aryan descent"] of the Nazis was mere patchwork), the floodgates to manipulation were opened in two ways: 1. Groups of persons could belong to the community of descent even if they do not belong according to the evidence of their language, religion or culture. The presumed descent makes it possible: Allegedly, the respective ancestors "lost" their "true" language or their "original" culture.¹² Since this was considered a violation against the "natural order", the affected groups needed to be "returned" to their "true ethnicity", e.g. through "re-education", forced conversion, language change and/or name change.¹³ If they offered "resistance", they were "traitors" and were treated as such.¹⁴ 2. A state could also have resident population groups that were deliberately excluded from the ethnically defined titular nation (especially Jews and Balkan Muslims)¹⁵ or did not allow the latter to include it ("assimilate"). Therefore, these groups were experienced as "alien" and a "threat". The results were endless "ethnicity struggles",¹⁶ including their accompanying symptoms: forced assimilation, ethnically motivated forced resettlements, expulsions and flows of refugees.

Forced migrations in the first half of the 20th century

Overall, four major complexes of forced ethnic migrations (without claim to completeness) defined by space and chronology can be differentiated in 20th century Europe. All occurred with some restrictions in the context of wars: 1. The Balkans and Asia Minor from before the start of the Balkan Wars of 1912/1913 to the signing of the Greek-Turkish Convention of Lausanne in 1923; 2. The Soviet Union in the 1930s and the 1940s; 3. The region between the Baltic Sea and Black Sea during and after the Second World War (1939 to about 1950), and 4. Yugoslavia and its successor states from 1991 to 1999. In addition to the forced migrations, there were formally (more or less) voluntary migrations (option right, emigration), which also succumbed to ethnic and national imperatives.¹⁷ Since it is impossible for a survey to treat all forced migrations, this article is limited to a selection.

The start-up of the forced migrations in the 20th century was provided by the Balkan Wars of 1912/1913, during the course of which ethnic cleansing on a large scale (forced rebaptism, forced name changes, expulsions and massacres) occurred that were fragmentarily documented by an international commission of observers from the Carnegie Foundation.¹⁸ The first internationally supported agreements on so-called population exchange followed. So-called population exchange because the quantitatively most significant agreement of these years – between Greece and Turkey in January 1923 – did not just initiate a new resettlement wave but also retroactively "legalized" the already completed flows of refugees and expulsions.¹⁹ There could be no question of an orderly resettlement. The plan to "unmix" the ethnic aggregate in a disputed region by exchanging minorities had already appeared a decade before the Lausanne agreement in a supplementary protocol to the peace agreement of 29 September 1913 between the Ottoman Empire and Bulgaria. It was the first interstate agreement in modern European history that provided for a population transfer between two states (but on a formally voluntary basis and limited to the inhabitants of border areas). Therefore, it went far beyond the option right entrenched in previous agreements. By contrast, the Greek-Turkish agreement of 1923 had a coercive character and extended to the entire respective state – with a few precisely defined exceptions relating to Orthodox Christians in Istanbul and Muslims in West Thrace.²⁰ To the extent that the affected persons had not already fled by 1922 during the final phase of the Greek-Turkish war (such as the majority of Greeks in Asia Minor), they were resettled by coercion.

The Treaty of Lausanne, which was negotiated under the auspices of the newly founded League of Nations, was another innovation in international law that was accepted (though with a bad conscience) as the ultima ratio for "solving" interstate conflicts. It served later actors, Adolf Hitler (1889–1945) as well as Winston Churchill (1874–1965), as a precedent and example.²¹ About 1.3 million Orthodox believers ("Greeks"), some of whom could not speak Greek, as well as almost 400,000 Muslims (of different linguistic and ethnic affiliations) lost their homes and previous citizenships. "Ever since the expulsion from Eden", a British geographer wrote in 1925, "man has been trekking, and folk wanderings are the roots of his history; but with 1922 began what may fairly be called history's greatest, most spectacular trek: the compulsory intermigration of two million Christians and Moslems across the Aegean Sea."²² Overall, the victims of the flight and expulsion waves from 1912 to 1923 add up to two or three million people (especially Greeks, Turks, Bulgarians and Macedonians).

The forced migrations in the Soviet Union of the 1930s and 1940s initially occurred in the context of Bolshevik "nation-building" and the forced restructuring of economy, society and culture.²³ In Transcaucasia, the Northern Caucasus and Central Asia, the gigantic "Modernization Concept" of the Bolsheviks encountered the massive resistance of the native population. Josef Stalin (1879–1953) and his comrades perceived this as the resistance of the nationalities conceptualized by him and punished it with mass deportations. Ethnic minorities in border areas and those that had a "home country" beyond the borders came into the visors of mass persecutions and were "prophylactically" resettled by force to Siberia or into the interior. The members of the respective national elites and wealthy peasants were deported east between December 1939 and June 1941 from the territories that the Soviet Union incorporated after the Ribbentrop-Molotov Pact of 1939 (the Baltic states, Eastern Poland, Bessarabia, northern Bukovina).

After Hitler Germany's attack on the Soviet Union, this policy escalated and resulted in the deportation of entire peoples and the dissolution of their autonomous republics and territories. During the summer and fall of 1941 the Soviet leadership deported the German population from the European part of the Soviet Union and the Caucasus to Central Asia and Siberia to prevent a feared collaboration with the German army. According to the data collected by the geographer and historian Pavel Polian, the total number of those deported for "prevention" in 1941/1942 was about 1.2 million, of these more than 900,000 were Germans (among them 440,000 Volga Germans). Men and childless women were drafted into the so-called labour army; the remainder of the population was locked up in "special settlements" and were declared to have lost their rights as citizens.²⁴ In the years 1943–1944 about one million members of other Caucasian and Turkic-speaking ethnicities who were classified as "unreliable", among them 412,500 Chechens, more than 190,000 Crimean Tatars and about 100,000 Kalmyks, followed, so that the number of ethnically classified deportations rose to about 2.3 million. About a third died during the transport and the first years in the destination areas. With the advance of the Red Army, the number of those affected once again increased: Apart from political opponents (members of the anti-communist resistance movements) and "class enemies" (for example, in the Ukraine, the Baltic states and Bessarabia), especially Germans in the conquered and Soviet-controlled territories (e.g. in East Prussia and Silesia, but also in Romania and Hungary) became victims of the persecution measures that consisted of deportation for forced labour into the Soviet Union and/or forced resettlement – unless they had fled in time. In 1945, the Soviet Union finally agreed on a population exchange with Poland according to the Lausanne "model": 1.5 million Poles from the Soviet Union and the former Polish eastern territories were "exchanged" against about 520,000 Ukrainians, Belarusians and Lithuanians. In the following year, a similar (though quantitatively less weighty) agreement was concluded with Czechoslovakia.

The period of the most extensive forced ethnic migrations ever in the history of Europe already began with the German attack on Poland in September of 1939. In his Reichstag speech of 6 October 1939, Adolf Hitler demanded that a "reordering of the ethnographic situation" in occupied Poland be immediately brought about by resettlement. The "Germanisation of Poland", already promoted in 1875 by the previously quoted Paul de Lagarde, could now take on a concrete form. Subsequently – and parallel to the broadening of the war – a series of repeatedly revised plans and designs for the Germanisation and colonisation of parts of eastern Central and Eastern Europe that were combined under the heading Generalplan Ost ("General Plan East") were created under the leadership of the agronomist Konrad Meyer (1901–1973)[] of the Friedrich-Wilhelm University in Berlin.²⁵ Heinrich Himmler (1900–1945)[], the SS leader and Reichskommissar für die Festigung des deutschen Volkstums ("Reich Commissar for the Strengthening of Germandom"), was responsible for the implementation. It never became possible to put into practice this monstrous programme, which provided according to various versions for the removal of 25 to 31 million people of "alien ethnicity" and "alien race" from their homes and the resettlement of 5.6 to 12.2 million Germans, "ethnic Germans" and "Germanised persons". However, the first measures for Germanising the conquered territories were already taken in late 1939. Initially, about 800,000 Jews and Poles were deported from the "annexed eastern territories" in Poland to make room for "German east settlers". These were mostly members of "ethnic German splinter groups", who were (forcibly) resettled from Estonia, Latvia, Galicia, Volhynia, Rumania, the Northern Bukovina and Bessarabia as well as eventually from Lithuania based on bilateral agreements.²⁶[] As a result, Volksdeutsche had become a mere cipher for manipulation that could be pushed back and forth at will. After the German attack on the Soviet Union in the summer of 1941 and the increasing radicalisation of the war, Germanisation and conquest of new living space (Lebensraum) continued on a grand scale in the East. The eastern campaign was perceived as a war of ideological worldviews and race-biological annihilation. Initially, the economic exploitation of the conquered territories and their people by forced labour stood in the foreground. About 2.5 million Soviet citizens were deported to Germany for forced labour. The Jewish population (about 2.1 million) and the Soviet leadership were systematically murdered. Millions of Jews, Poles, Russians and other population groups in eastern Central Europe and Eastern Europe became victims of the Nazi settlement and annihilation policies. In the states of South-eastern Europe occupied by Germany or allied to it, many population groups were forcibly resettled, expelled or driven into flight due to their ethnicity.²⁷

With Germany's defeat, the direction of the great forced migrations became reversed. Flight, expulsion and resettlement now proceeded from east to west: for example, from the parts of Poland conquered by the Soviet Union to Poland and from Poland into the occupied zones of Germany. Already during the war the British Prime Minister Churchill spoke for a "westward shift" of Poland and an "untangling" of territories of mixed nationality. He repeatedly invoked the "successful" Lausanne model of 1923 in the process.²⁸ At the Potsdam Conference the "Great Three" (Churchill, Stalin and Truman) announced in their Final Protocol of 2 August 1945 that they "recognize that the transfer to Germany of German populations, or elements thereof, remaining in Poland, Czechoslovakia and Hungary, will have to be undertaken." This resettlement was to proceed in an "orderly and humane manner". The governments of Poland, Czechoslovakia and Hungary were requested to stop further expulsions ("wild" expulsions) until the Allied Control Council for Germany had agreed on a just distribution and pace of the expulsions. The great majority of the German population in these three countries and Yugoslavia lost its homes towards or after the end of the war. Some fled or were evacuated, others fell victim to "wild" expulsions and retaliation, while the rest were forcibly resettled (sometimes for a repeated time).[] 12 to 14 million people were affected, of whom many did not survive the hardships.²⁹ They have justifiably been called "Hitler's last victims".³⁰ In the territory of Poland alone (within the boundaries before the Second World War), more than 20 million people of various nationalities (but especially Germans and Poles) are estimated to be caught up in the machinery of forced ethnic migration.

From Lausanne to Dayton: International paradigm shift

After the end of the third wave of forced migrations, war, mass murder and expulsion seemed to have definitively become a thing of the past – at least in Europe. Therefore, the international public reacted with all the more shock to the ethnic cleansing in the former Yugoslavia (1991–1999). The Serbo-Croatian war in Croatia, which lasted with interruptions from 1991 to 1995, the Serbian-Muslim-Croatian war in Bosnia (1992–1995) and the ethnic cleansing in Kosovo (in the second half of the 1990s) developed into ethnic wars par excellence, but not in the sense of causing the war, for it was not "atavistic hatred" between the peoples of Yugoslavia. Rather, stoking of national threat scenarios, the revitalisation of old propagandistic images from the Second World War, and unbridled hate campaigns prepared the ground for the wars. However, once violence had started (as a rule by paramilitary gangs and "special units"), it created a new order and split the population into ethnonational conflict parties. About 150,000 to 180,000 people became the victims of these orgies of violence and 3 to 4 million people were driven out or fled. In Bosnia-Herzegovina alone, 2.3 to 2.5 million of the original 4.4 million inhabitants lost their homes through flight, expulsion or mass murder (in the first place Bosnian Muslims/Bosniaks, but also Bosnian Serbs and Croats). The genocide of about 8,000 Bosniaks near Srebrenica in July 1995 marked the climax of ethnic cleansing.

The understanding between Croats and Bosniaks, which came about under American pressure, the successes of the Croatian offensive against the "Serbian Republic of Krajina" in Croatia and NATO's air raids, which were taken up after long hesitation, forced the Serbs, who were initially militarily superior in Bosnia and at times controlled almost 70 percent of Bosnia-Herzegovina's territory, to give in. On 1 November 1995 the president of Bosnia-Herzegovina, Alija Izetbegović (1925–2003), the president of Croatia, Franjo Tudjman (1922–1999), and Serbia's president, Slobodan Milošević (1941–2006), met on the US air force base Wright Patterson in Dayton/Ohio to agree on a final peace for Bosnia-Herzegovina based on already existing plans and under strong pressure from the American negotiator Richard Holbrooke (1941–2010). The negotiations were completed on 21 November and the Dayton Accord was officially signed on 14 December 1995 in Paris. In Appendix 7 of the framework agreement, the parties to the agreement committed themselves as much as possible to reverse ethnic cleansing and to enable refugees and displaced persons to return to their home areas, to restore former property rights or, where this is not possible, to compensate them appropriately.³¹

With this, the international community underwent a fundamental paradigm change 73 years after Lausanne. The "logic" of Lausanne rested on the assumption that the ethnic/religious heterogeneous settlement structure in parts of Anatolia and the attached national irredentisms were the cause of the Greek-Turkish war. The cause of the war was to be eliminated by "unmixing" the agglomerations. In fact, the Greek Megali idea (the "Great Idea"), that is the vision of a "Greece of the two continents and five seas" or the idea of a restoration of the Byzantine Empire was definitively carried to the grave at Lausanne, allowing the Greek-Turkish relationship to relax during the 1930s. The price was paid by the traumatised refugees and forcibly displaced persons. But why was the logic of Lausanne, which was shared beyond the Second World War by many, very different political actors, given up in the Dayton Accord? Decisive was the repeated international condemnation of expulsions since the Nuremberg War Crimes Trials,³² the reports on ethnic cleansing and the worldwide distributed images of terror from former Yugoslavia, which strengthened in large segments of the public in Europe, the USA and other states the determination to no longer accept facts created by ethnic cleansing (at least not in Europe). Regardless of the fact that the wars in former Yugoslavia were interpreted by many observers as an expression of "atavistic" animosity between peoples, the "humanitarian logic" prevailed that "unmixing" cannot be accepted as a means for solving ethnonationally associated conflicts. At this point, one can only speculate on the success of the paradigm shift.³³

Motives and implementation forms of forced ethnic migrations were similar in all cases during the 20th century. What changed were the national or ethnic labels of the affected and the actors. Sometimes it was Greeks and Turks, sometimes Germans, Poles and Russians, sometimes Hungarians, Slovaks and Czechs, sometimes Croats, Serbs, Albanians, Bosnians etc. In Central, South-eastern and Eastern Europe there is hardly a nation or ethnic group whose members were not in one or another form and to one or another extent forced to leave their home during the course of the 20th century. They were forcibly resettled, expelled or fled because they belonged to a particular nation or nationality or were allotted to it, regardless of individual incrimination. The cause was always an absolutising of the nation and the associated stereotypes of oneself and others, which especially in times of crisis and war darkened the mutual patterns of perception and images of enemies to unrecognisability. The threat scenarios stoked by intellectuals and politicians created outward delimitation and inward solidarisation. They created a group thought that only few in the camp of the perpetrators and the camp of the victims could escape. At times, perpetrators became victims and victims became perpetrators. Nevertheless, it is historically wrong to place perpetrators who became victims and victims who became perpetrators on the same level because this neutralizes cause and effect. Violence begets violence as well as an extremely polarised new order that did not exist beforehand and comes to determine action. Therefore, the question of who set the spiral of violence in motion and in whose name is historically always decisive. For, once it has been set in motion, it generates its own dynamic that forces its destructive logic on all the affected alike (perpetrators and victims), dooming also those as well who are not among its originators.

Holm Sundhaussen