1Observing boundaries as an empirical manifestation of the spatial and temporal limits of societies (Jacob, Von Asche, 2014) is an exciting research perspective in social science. From the second half of the 19th Century to the beginning of the 20th Century, geographers have been working continuously on borders, in relation to various themes: political division of space, territoriality and exercise of power. All this research has been one of the most obvious manifestations of the link between this discipline and the construction of the modern state. It was during this period that a true geography of borders emerged, based on the work of Friedrich Ratzel (1844-1904), Jacques Ancel (1879-1943) and Halford J. Mackinder (1861-1947), among others. Very quickly, two conceptions were distinguished or even opposed. On the one hand, French geographers conceived the border as a social construction that may or may not be based on a natural element. For example, Jacques Ancel then defined the frontier as a meeting line between two contradictory political forces (Ancel, 1938). On the other hand, a German conception emphasized the relations between people and space. In this conception, the border is seen as a living entity and it is moving; it is the spatial mark of the geopolitical action of a state between two phases of expansion. Beyond these differences, three ideas gradually imposed themselves and formed the framework for research until the 1970s: borders are never natural; they are neither fixed nor permanent; they are both lines and more or less wide areas where exchanges between neighboring social groups take place. A fourth idea, linked in particular to the functionalist perspective developed in a significant contribution by Richard Hartshorne, is linked to the three previous ones: borders are the boundaries of states -in the Westphalian conception- and states are the basic “social containers” which define the world system (Agnew, 1994; Taylor, 1985). Within this framework, different approaches have been developed and have made it possible to draw up classifications based on criteria such as the age of the borders, their functions (contact or separation borders, military or economic borders, etc.), their legal status and the intensity of the socio-economic relations that cross them, etc. In this respect, the work of Hartshorne on the historical dynamics of boundary delineation, particularly in relation to settlement dynamics, has been again a significant milestone (Hartshorne, 1933 and 1936).
2From the 1970s onwards, new research perspectives appeared in a context marked by several major facts: the gradual end of the discrediting of geopolitics (after Nazism and Second World War consequences), the progressive liberalization of international economic relations and, above all, the fear of economic, social and cultural standardization under the effect of globalization... In addition, a major change in the social sciences has had an impact: the emergence of critical theories that have renewed the ways of doing geopolitics and studying fundamental objects such as boundaries (ó Tuathail, 1996). Besides, the collapse of the Soviet Union and the end of the Cold War world order paved the way in the 1990’s for a new panorama and a reconfiguration of the borders map, especially in Central and Eastern Europe. In this context, researchers were faced with a theoretical-empirical scenario that was unthinkable a decade earlier. Scholars then began to study border areas and margins, marked by particular social functions and spatial dynamics. Borders are still seen as instruments for controlling flows (Kolosov, Scott, 2013; Moullé, 2013) but increasingly also as multidimensional and dynamic social constructions (Raffestin, Guichonet, 1974; Kolosov, 2011; Amilhat Szary, 2015a and 2015b). They are observed in order to study societies and better understand their relationship to space. Academic research is then focused on the social impact of national borders on local populations and regional economies, and on the populations that populate the edges of borders. Anssi Paasi’s work on the Finnish-Russian border is emblematic of these renewed approaches that focus on the practices, discourses and social representations of space associated with border (Paasi, 1996 and 1999). This work offers a twofold perspective: the border is seen as a political discontinuity between two states and it is important to observe the conditions of appropriation of this border by local populations.
3Since about the beginning of the 2000s, geographers have been observing borders as a complex object to identify the major contemporary changes in the world: the removal of borders within the European Community and other regional blocs, the appearance of new borders along certain strong discontinuities between rich and poor countries, the emergence of new linguistic and cultural discontinuities, mobility of individuals and virtual mobility via the Internet, etc. Approaches are diversifying, as are the fields of observation. Borders are less and less studied from a strictly geopolitical perspective. Starting from the empirical observation that borders are complex objects, research dedicated to them in geography follows several directions (Popescu, 2011), ranging from classical to post-modern approaches (Kolosov, 2005 and 2011). In the classical approaches, researchers were interested in the delineation of boundaries as such (Minghi, 1963; Prescott, 1987), in what Michel Foucher calls horogenesis (Foucher, 1991). Today, there is less interest in the boundary line that defines a field of sovereignty than in the territorial margins of states, which can be blurred, i.e. border zones (Newman, 2006). Moreover, research shows that border regions are places where populations construct particular forms of spatial organization, using the border alternately as an instrument of separation or contact, depending on the context (Amilhat-Szary, 2015a and 2015b). As a matter of fact, local and regional territorial agents shape new territorialities at cross-border dimension: euroregions, eurodistricts, eurocities are currently covering all the European borders (Noferini et al., 2020). More fundamentally, in the context of the growing mobility of goods and people and in the context of globalization, it is clear that the traditional forms and functions of the border are tending to diminish and reappear in other unconventional forms, in highly important places in social, political and economic terms.
4The attention of researchers is then focused on the multiplication and sophistication of networks, on the spatial inscription of borders and on the behaviour of territorial actors in relation to these changes. A few research themes are then given priority: the relationship between borders, major networks, transport and communication nodes; the relocation of borders in terminals of all kinds (airports, space, sea or river ports, bus and railway stations, etc.); the changing shape of borders that are less linear and increasingly located in control points that are multiplying within reticular spaces. At the same time, borders are studied at infra or supra-state levels. There is a growing interest in social borders defined as internal boundaries within a society. Similarly, interest is being paid to lines that were previously perceived as mere administrative boundaries and that are emerging as new intra-state boundaries as a result of decentralization, privatization and supra-state constructions. One of the reasons for this is the weakening of states (Agnew, 1994; Faludi, 2018), whose traditional functions are sometimes taken over by different local actors (local chiefs, mafias, private companies, residents’ groups, etc.) who eventually take the place of public power. At the same time, research is focusing on what some social groups and individuals perceive as an excessive openness to the globalized world. This perception translates into a reaffirmation of borders in certain parts of the world, in relation to security, migration, economic and identity issues...
5It is not surprising that despite, or because of, globalization, the demand for borders remains strong. Since 1991, more than 26,000 km of new inter-state borders have appeared. In addition, border conflicts remain topical and are on the increase in many parts of the world. There are approximately 252,000 km of international land borders today and a growing number of disputes (India and China, India and Pakistan, Russia and Ukraine, Morocco and Spain, Ireland, Georgia...). The world remains largely Westphalian in its jurisdictions. Border conflicts take several forms: border disputes by cross-border populations (Kurds, Pashtuns, Bosnians of the Sandjak, Magyars, Albanians), symbolic conflicts linked to secessionist movements (Kosovo, symbol of the Serbian nation but populated by 2 million Albanians), sharing of resources (Sudan, eastern Mediterranean, South China Sea, Nile), frozen border conflicts (Moldova-Transnistria, Russia-Estonia, Peru-Chile...).
6These facts show that the hypothesis of the disappearance of borders is ultimately an illusion. We are witnessing the persistence, if not the return, of borders. Moreover, in some countries, traditional borders no longer seem to be sufficient and impenetrable walls are being built against foreigners. Nation states are readily accused of being powerless in the face of transnational and global forces and of being dominated by cosmopolitan elites ignoring the will of the people. The desire for borders illustrates the desire to restore strong states led by leaders who embody the “sovereign people”. The effects are varied: tightening of migration policies, construction of physical barriers (Hungary, Austria, Slovenia, Bulgaria, Ceuta and Melilla, United States, Israel, India and Bangladesh), militarization (North and South Korea, Western Sahara, Cyprus...), renewal of border walls to defend against the migrant, the poor or the terrorist. The changes in the spatial forms of borders are so dramatic that much research has been directed towards the so-called debordering and rebordering of political spaces (Andreas and Biersteker, 2003). Succeeding the initial stage of the contemporary bordering of the assertion of state sovereignty (Arbaret-Schultz, 2008), debordering is marked by the reduction of border effects in order to promote trade and circulation. Conversely, rebordering is marked by the reactivation of certain border functions on the symbolic and material levels. Above all, however, the porosity of borders to trade and mobility is combined with their selective closure. The modes of functioning of borders, which some researchers call border regimes, are diversifying, in relation to the political choices of states. Some borders also function as filters, capable of opening and closing at the same time as selective barriers thanks to the intensive use of technology (digitization, detection and surveillance devices, smart borders) (Popescu, 2011).
7Regional integration offers a very favorable context for these dynamics, in the European Union and in other more or less deeply integrated regional associations such as the United States-Mexico-Canada agreement, customs unions or common markets in Africa, South America and South-East Asia (Kolossov, 2005). In the case of the European Union, integration goes hand in hand with the development of sophisticated mechanisms to foster territorial cooperation at different scales and to implement new supranational or transnational territorial meshes of political action, which are considered more relevant for addressing certain challenges (migration and mobility management, territorial development, environmental management and protection, energy supply). But European integration is today in crisis and the European project is facing political, cultural and socio-economic delegitimization. In this context, internal and external borders are at the heart of an institutional, academic and public debate. The process of weakening borders, which has been promoted since the 1980s by the member states and by the European institutions (single market, economic and monetary union, political union and cohesion policy), is today faced with a demand for the strengthening of borders by some elected representatives and citizens, who are questioning the foundations of the European project.
8This issue of Belgéo is drawn from the 6th Eugeo’s congress held in Brussels during the first days of September of 2017 (“Geography for Europe”). It brings together six contributions to the analysis of the ambivalent and multiscalar nature of borders in Europe. It is focused on Central and Eastern Europe and Balkans, i.e. on countries marked by intense and dramatic experiences in defining and changing borders, with a very recent memory of the last modifications. The authors of these articles have different points of view, but all of them demonstrate to what extent borders - present or past, administrative or mental - are not a secondary fact in the social construction of space; to what extent they are or can be determining elements of the present and the future, although they are neither natural, fixed nor permanent.
9We see every day that they play a major role in the debates that cross or even divide public opinion in several countries such as Ireland (Brexit and backstop), the countries of the Visegrad Group (migration issue)... At the micro level, geopolitical questions are just as relevant. Border urban and metropolitan areas have specific socio-economic characteristics and functions (Durand, Perrin, 2017). Border societies and local identities are partly determined by the impact of the border on daily practices. In this context, the ambivalence of the border as both a resource and a handicap for local development is a crucial aspect (Sohn, 2014).
10It is at the micro-local level that Marta Zorko and Nikola Noval propose to observe the border, in the town of Vukovar, located in eastern Croatia on the border with Serbia, i.e. on the external border of the European Union. This town, one of the most intensively bombed in Europe since the Second World War, was besieged by the Serbs in the 1990s. It is usually portrayed as a divided city with a mental and geopolitical divide. M. Zorko and N. Noval propose a critical study of this representation, based on field research conducted among the inhabitants in 2018.
11Mykola Dobysh and Boris Yatsenko look at the external periphery of the European Union by focusing on the electoral geography of Ukraine. In a critical approach, they also analyse and question the relationship usually established between the cultural geography of this country (languages, ethnicities, identities) and the electoral geography. By testing the hypothesis that social structure can have an influence on regional electoral polarisation, widely disseminated by numerous studies in the 2010’s, they reassess the role of language and national belonging in Ukrainian political geography.
12Another important theme is the territorial effects of European integration. What are the impacts of European territorial cooperation on reducing obstacles to the development of cross-border regions? The Interreg programmes have generated thousands of cross-border projects, involving a plethora of actors of all kinds and levels, and taking place in many territories (Reitel, Wassenberg, 2015; Feliu et al., 2019). However, it remains difficult to measure the effects of these programmes. To gain a clearer picture, it would be necessary to multiply local empirical studies, proposing comparative, quantitative and qualitative approaches that would take into account the historical, geographical and institutional specificities of the places concerned (Berzi, 2017; Garrard, Mikhailova, 2018).
13Martin Barthel proposes in his article a comparative study of local territorial development on the western and eastern borders of Poland since 1989 (borders with Germany and Ukraine). He focuses in particular on the daily practices of the residents of these regions. How does the border influence their practices? How is the border used by local residents? Does it influence the way they perceive people living on the other side? Is the border a line/place of connection or disconnection between the riparian territories?
14Imre Nagy, for his part, is interested in the different types of networks of actors involved in territorial cooperation projects involving border municipalities in the European Union, on the borders of Hungary, Croatia, Serbia and Bulgaria. His attention is focused on the weight of local municipalities in the structuring of cooperation networks and on the use of European funds financing projects.
15Finally, the historical legacies of borders in Eastern Europe remain an important subject, even thirty years after the demise of the Soviet order. In the internal and external peripheries of the European Union, some of them are geopolitical issues of primary importance threatening the stability of the entire continent. In the former Eastern Europe and in the former Soviet space, there are what can be called “ghost borders” from the past.
16Vladimir Kolosov observes these borders. He points out that the redefinition of state borders after the Second World War, decolonization and break-up of certain political constructions (Yugoslavia, USSR), have given rise to a new interest in the former political borders and in the drawing of so-called “fair” borders. This stems from the fact that once a border has disappeared (ghost border, which is a special type of “relict borders”), it leaves marks, sometimes deep and lasting, in the organization of space, in practices and in social representations. It sometimes eventually turns into a mental border and maintain a certain legitimacy on the ground over time. Elaborating on this postulate, and picking up examples in various part of the world, especially in Europe, he tries to answer some basic questions. What is the impact of the political boundaries of the past on the current cultural landscape? Are the “old” borders that have now disappeared less important than the more recent ones? Why are some old borders more visible than others? What is their role in strengthening or constructing territorial identity, and in shaping contemporary cultural and political territorial models? What conceptual and theoretical framework should be used to study them?