University of Birmingham Migration diplomacy in world politics

: Academic and policy debates on migration and refugee “crises” across the world have yet to engage fully with the importance of cross border population mobility for states’ diplomatic strategies. This article sets forth the concept of “migration diplomacy” as an object of analysis for academics and practitioners alike, distinguishing it from other forms of migration-related policies and practices. It draws on realist approaches in international relations to identify how the interests and power of state ac- tors are affected by their position in migration systems, namely the extent to which they are migration-sending, migration-receiving, or transit states. The article then discusses how migration issues connect with other areas of state interest and diplomacy, including security interests, economic in- terests and issues of identity, soft power, and public diplomacy. Finally, the article suggests the utility of applying a rationalist framework based on states’ interests in absolute versus relative gains as a means of examining the bargaining strategies used by states in instances of migration diplo- macy.

Keywords: migration, diplomacy, refugees, bargaining, issue linkage The significance of "migration diplomacy" to contemporary world politics can be seen in two recent examples, drawn from the post-2011 Syrian refugee crisis. In February 2016, King Abdullah of Jordan declared that Jordan was at "a boiling point" because of an influx of Syrians (Doucet 2016). Two days later, a donor conference in London adopted the Jordan Compact, granting the country $1.4 billion in aid in the 2016-18 period. In the same month, Turkish President Recep Tayyip Erdogan adopted a more aggressive stance toward the European Union (EU): "We can open the doors to Greece and Bulgaria anytime and we can put the refugees on buses," he declared in Brussels. "So how will you deal with refugees if you don't get a deal? Kill the refugees?" Erdogan asked European Council President Donald Tusk (Reuters 2016).
With a rise in the number of migrants in the world to 244 million in 2015, including more than 21 million refugees fleeing war and persecution, the "global migration crisis" has been dominating headlines (United Nations 2016). Much of the focus has been on the humanitarian and domestic political consequences of cross-border population movements: thousands of migrants and refugees have died in attempts at crossing the Mediterranean, while in the United States immigration issues played an important role in the 2016 presidential election campaign. 1 In the run-up to the United Kingdom's vote on Brexit, anti-EU media and political elites employed the issue of immigration to play to public anxieties about terrorism, economic dislocation, and national sovereignty. Elections across EU countries and elsewhere have also put refugee and immigration policies to the forefront of public debate. Meanwhile, states such as Turkey, Lebanon, and Jordan have struggled to accommodate the almost 5 million forcibly displaced from the neighboring Syrian conflict (Okyay 2017;Vignal 2017) and Greece, Italy, and other countries in Europe were confronted with a rapid influx of approximately 1 million border-crossings by migrants and refugees in 2015 alone.
In the midst of such developments, less attention has been paid to some of the other ways in which population mobility is impacting the conduct of politics in the twenty-first century, including in the fields of interstate relations and diplomacy. As Hollifield (2004) has argued, the contemporary state is a "migration state," one in which the management of migration flows is a central component of state functions and interests-just as, in previous eras, states were defined by their ability to make war or engage in trade (Rosecrance 1986). States have developed a wealth of policies across different areas that aim to respond to or regulate various forms of human migration and mobility, both voluntary and involuntary. At the same time, states also attempt to manage the domestic impact of migration, paying particular attention to the effects of population mobility at the economic (Passaris 1989), security (Adamson 2006), political (Brubaker 1989), and sociocultural levels (Levitt 1998). Yet, migration impacts the conduct of politics beyond domestic policymaking, including in the area of international diplomacy-or the ways in which states negotiate and conduct their affairs with each other and with other entities such as international organizations (Sharp 2009;Hamilton and Langhorne 2011). Heightened migratory flows across national borders affect states' diplomatic interactions with other actors in the international system and become the object of interstate diplomacy. This is not an entirely new phenomenon (Choucri 1977;Teitelbaum 1984;Weiner 1992;Greenhill 2010;Thiollet 2011;Gabaccia 2012;Oyen 2015), but it has heretofore received relatively little systematic attention from scholars and practitioners alike.
The aim of this article is to begin to address a gap in the international relations (IR) literature by theorizing "migration diplomacy" as an object of study and research. We do so by first discussing the concept of migration diplomacy and its scope conditions, distinguishing it from other forms of migration-related research, such as research on citizenship, integration, or diasporas. Second, drawing heavily on realist approaches in international relations, we outline how the interests and power of state actors are affected by their position in migration systems according to whether they are migration-sending, migration-receiving, or transit states. Third, we discuss how migration issues connect with other areas of state interest and diplomacy, including security interests, economic interests and issues of identity, soft power (Nye 2004), interdependence (Keohane and Nye 1977), and public diplomacy. Finally, we suggest the utility of applying a rationalist framework based on state interests in absolute versus relative gains (Powell 1991) as a means of examining the bargaining strategies used by states in instances of migration diplomacy, before concluding with some thoughts regarding areas for further research.

Migration Diplomacy: Definitions and Scope Conditions
Just as states engage with one another in areas relating to war and peace, trade, economics, culture, the environment, and human rights, migration is increasingly an important area of states' bilateral and multilateral diplomatic relations. Despite a growing range of work on the complex facets of modern diplomacy, migration has yet to feature in such analyses, even though it is prevalent in practitioners' strategies. Examples include intergovernmental agreements that aim to encourage-or limit-migratory flows; the extension of preferential treatment to certain foreign nationals; the creation of guest-worker or other temporary labor migration schemes; the expulsion or threat of expulsion of foreign nationals; and so on. This is not to say that there is an absence of work on the interplay between foreign policy and population mobility. Indeed, there is a significant literature in this area, primarily focusing on immigration across OECD states (e.g., Tempo 2008;Hollifield, Martin, and Orrenius 2014). In addition, scholars in the field of refugee studies have also examined related issues, such as the use of "suasion" in North-South bargaining over refugee protection (Betts 2009); the use of refugees by irredentist host states in cross-border conflicts (Salehyan and Gleditsch 2006;Salehyan 2007); and the realpolitik motivations of host state governments for admitting refugees (Jacobsen 1996;Whitaker 2002). Similarly, the growing field of state-diaspora relations and diasporic activism has engaged with matters of foreign policy (King and Melvin 2000;Adamson and Demetriou 2007;Koinova 2011;Adamson 2016;Tsourapas 2016).
This article builds on this work and suggests the utility of the term migration diplomacy to describe states' use of diplomatic tools, processes, and procedures to manage cross-border population mobility. 2 It is important to delineate the scope of migration diplomacy and to be clear about what it includes, but also what it excludes. Not all attempts to manage migratory flows constitute migration diplomacy, nor should the whole gamut of issues related to migration and migrants' affairs fall under the scope of migration diplomacy. In addition, it should be noted that any state's ability to effectively use diplomatic tools and processes in relation to migration processes will be dependent on other factors, such as its overall power and available resources.
Three main scope conditions apply to our definition. Firstly, migration diplomacy refers to state actions and investigates how cross-border population mobility is linked to state diplomatic aims-as such, it does not investigate the internal workings of international organizations, the media, or social actors, such as nongovernmental organizations-although it is possible to apply the framework to statelike international actors, such as the European Union or even the United Nations High Commissioner for Refugees. 3 Indeed, states often engage in migration diplomacy vis-à-vis international organizations-for example, states such as Tanzania have made exaggerated public appeals to the United Nations High Commissioner for Refugees and other actors as a way of securing resources (Whitaker 2002). Kenya may have used threats to close the Dadaab camps as a type of diplomatic bargaining chip, and countries such as Denmark sometimes engage in direct public diplomacy as a means of deterring unwanted migration. 4 While globalization has diminished the monopoly of the sovereign state in world politics, the state is still the main actor in the regulation of cross-border population mobility and is likely to continue to be so, especially with the recent rise in populist nationalism and the renewed significance of borders. As Torpey (1998) has noted, a key feature of modern nation-states is that they not only have a monopoly over the legitimate means of violence, but also the legitimate means of movement. Their territorial logic means that they have an interest in maintaining and controlling their national borders as an aspect of their domestic, Westphalian, and interdependence sovereignty (Krasner 1999;Adamson 2006).
Secondly, a state's migration diplomacy is not synonymous with its overall migration policy-migration policies may range from completely restrictive to allowing free migration (Messina and Lahav 2006;Hollifield et al. 2014), but these are only relevant when states include them as part of their foreign relations and diplomacy. For example, standard elements of migration policy such as the issuing of visas, the control of borders, or a state's refugee and asylum policy are not in and of themselves elements of migration diplomacy. Typically, US visa policy is not shaped by diplomatic priorities in the United States; that said, in some instances it has also been used as a migration diplomacy tool during interstate bargaining processes-as for example occurred in the October 2017 dispute between Turkey and the United States when there was a tit-for-tat imposition of travel and visa restrictions (Shaheen 2017). Diplomacy is often about negotiation, and migration diplomacy centers on how states employ cross-border population mobility management in their international relations, or how they use diplomatic means to obtain goals relating to migration. In other words, migration diplomacy can include both the strategic use of 2 In doing so, we build on the important work of Gabbacia (2012), Greenhill (2010), Oyen (2015), Thiollet (2011), and others who have noted the relationship between migration and various forms of state diplomacy. Thiollet (2011, 110), for example, introduced the concept of Arab "migration diplomacy," although she used the term in a broader sense to include informal and private actors.
3 This is not to say that some insights gleaned from a focus on migration diplomacy would not be of interest for understanding the policies or actions of nonstate actors. Indeed, we would expect that just as the literature on paradiplomacy has applied concepts of state diplomacy to nonstate actors, similar parallels could be found in the area of migration diplomacy and paradiplomacy. 4 We thank an anonymous reviewer for suggesting these examples. migration flows as a means to obtain other aims 5 or the use of diplomatic methods to achieve goals related to migration. Finally, migration diplomacy highlights the importance of the management of cross-border mobility as an international issue-thus, it needs to be analytically disassociated from a wealth of migration matters that, however political, do not have a direct impact upon interstate relations; internal displacement, the regulation of immigrants' citizenship status or access to rights, tariff rules determining which goods migrants are able to transport, diaspora politics, and the welfare of refugees are only relevant to migration diplomacy insofar as they impact on interstate interactions. 6 For instance, a state may in some cases institutionalize diaspora engagement policies-such as preferential investment conditions for diaspora members-largely for reasons of promoting domestic economic development. Internal displacement is a major global migration issue-with millions displaced annually due to conflict, violence, and natural disasters-yet it may often be wholly unrelated to issues of interstate diplomacy.
A prominent recent example that fits our definition of migration diplomacy is the March 2016 agreement between Turkey and the European Union. In this case, Brussels agreed to provide Turkey with 6 billion Euros, accelerate its membership application, and provide visa-free access for its citizens to Schengen-the 26-country area in Europe that has abolished internal passport controls. In exchange, Turkey would strengthen its external borders and accept the return of irregular migrants from Greece. For every Syrian returned to Turkey in the scheme, the European Union pledged to resettle another in Europe, up to a cap of seventy-two thousand. In November 2016, as the European Parliament voted to suspend EU membership talks with Turkey, the Turkish president threatened to renege on the agreement: "if you go any further," President Erdogan warned, "these border gates will be opened. Neither me nor my people will be affected by these dry threats. It wouldn't matter if all of you approved the vote" (Mortimer 2016). For Erdogan, the Eastern Mediterranean country's unique position and ability to control the flow of refugees and migrants into the European Union constituted a key bargaining chip in Turkish migration diplomacy (İçduygu and Üstübici 2014; Greenhill 2016).
But migration diplomacy is neither a recent nor a distinctly European phenomenon. In the early decades of the Cold War, the Soviet Union's restrictive policies prevented the emigration of Jewish citizens (Peretz 2015). Concerted American migration diplomacy during the détente years facilitated the exodus of Soviet Jews (Beckerman 2010). Similarly, the regulation of Mexican laborers' migration into the United States has historically been a central issue in the two states' bilateral relations, with the Bracero program being a prime example (Délano 2011). Entering into effect in 1942, the Bracero program regulated the immigration of Mexican manual laborers (braceros) to the United States for more than 20 years and was subject to a number of revisions according to the two states' economic and political interests. Until its termination in 1962, the program oversaw the arrival of more than 4.5 million Mexicans into the United States. For 20 years, bilateral migration diplomacy produced multiple political spillovers, such as close cooperation in the fields of security, law enforcement, and irregular migration control across the US-Mexico border. Mexican migration diplomacy efforts in the 1970s, aiming to revive such cooperation, were unsuccessful as the United States had little to gain from a new Bracero program: "The US government saw little reason to resume the program while undocumented immigrants continued to meet US labor demand," argues FitzGerald (2006, 277)-"Both governments grew to accept, at least tacitly, massive undocumented migration" (Ibid).
Having discussed the concept of "migration diplomacy" and its scope conditions, we now turn to examining how power relations operate in instances of interstate bargaining around migration issues. As the examples of both the Turkey-European Union and Mexico-United States cases illustrate, interstate bargaining around issues of migration often takes place between states with an asymmetrical power relationship. Indeed, Greenhill (2010, 23ff) has noted that the manipulation of migration flows for the purposes of projecting power is a strategy commonly employed by weak actors. States that lack capacities in other areas can at times attempt to leverage the issue of migration to enhance their bargaining position vis-à-vis more powerful states. In the following section, we elaborate on this by discussing the varied power and interests that states have due to their different positions in migration systems and their roles as migration-receiving, migration-sending, or transit states.

State Power and Interests: Sending, Receiving, and Transit States in Migration Diplomacy
Migration diplomacy functions similarly to traditional diplomacy in that it is shaped by the interests of and existing power relationship between states. Just as important as military and economic indicators of a state's power and interests, however, is its position in the web of global migration flows. A migration diplomacy framework conceptualizes states as deriving their interests and bargaining position vis-à-vis other states based in part on whether they are migration-receiving, migration-sending, or transit states-in other words, whether their main concerns are with respect to immigration, emigration, or transit migration. 7 These, it should be clarified, are ideal types and a state may simultaneously hold the position of migration-receiving state in some bilateral relationships while holding the position of sending or transit state in others.
Receiving states, as a type, are primarily concerned about the dynamics of immigration and typically manage inflows of people. For example, the United States currently hosts the largest number of immigrants, estimated at approximately 47 million, or one-fifth of the world's total (United Nations 2015). Washington has, understandably, developed a complex immigration diplomacy framework that primarily focuses on immigration from Mexico and other Central and Latin American countries (Martin 2014). A less-examined aspect would be Washington's practices throughout the second half of the twentieth century, given its antagonism to China (Gabbacia 2012;Oyen 2015), and the Soviet Union. Identifying potential defectors from the Eastern bloc, cultivating these contacts, and arranging for their eventual relocation into the West constituted a key aspect of American immigration diplomacy during the Cold War (Krasnov 1985;Toft 2007).
Beyond receiving states and immigration diplomacy, sending states constitute a second group of actors that engage in migration diplomacy. These states are primarily concerned with the dynamics of emigration, or the outflow of people. Emigration diplomacy can be identified in a number of sending states' policies, both currently and historically. Emigration diplomacy practices are often identified in states of the Global South. Egypt, for instance, constitutes the largest exporter of labor in the Arab world, and its emigration diplomacy underwent two broad periods. Under President Gamal Abdel Nasser, the Egyptian state would promote the emigration of teachers, lawyers, and other high-skilled professionals across the Arab world throughout the 1950s and 1960s for political purposes, as many of these Egyptians engaged in pro-Egyptian activism abroad (Chalcraft 2010;Tsourapas 2016).
More recently, Egypt's emigration diplomacy has focused on bilateral collaboration, rather than interstate antagonism; the dispatch of skilled Egyptian labor to the oilproducing Arab states was part of President Anwar Sadat's emigration diplomacy from the 1970s onward, aiming for rapprochement and close diplomatic relations with the economically powerful Gulf states (Feiler 2003;Tsourapas 2015).
Finally, transit states are third countries that are neither countries of origin nor destination. These states are able to engage in transit migration diplomacy usually because of their geopolitical location as part of a migrant route. While Mexico, for instance, is often portrayed as an emigration state vis-à-vis its migrant population in the United States, it also enjoys a key regional status as a transit state. A rising number of migrants from the Central American "Northern Triangle," namely Honduras, El Salvador, and Guatemala, attempt to enter the United States by crossing through Mexico. President Felipe Calderón's transit migration diplomacy was shaped by the need to maintain the US-Mexico relationship. As a result, Central American transit migrants were perceived as a security issue, while Mexico alienated Central American governments by implementing "hostile policies" on its borders. More recently, under Peña Nieto, Mexico shifted its transit migration diplomacy policy toward a framework of "shared responsibility" (corresponsabilidad) with Central American governments, with a greater emphasis on regional cooperation on the issue (Donnelly 2014).
The example of Mexico highlights how these three categories are far from fixedalmost all states experience some degree of both immigration and emigration, a mix that may also change over time. Germany, for example, was a major exporter of migrant labor until the early twentieth century; the 2000 United States census identified 46.5 million citizens, or 15.2 percent of the population, as claiming Germany ancestry (Baker et al. 2004). For the latter half of the twentieth century, the country shifted to be a significant importer of unskilled and low-skilled labor in order to sustain its post-World War II reconstruction and redevelopment, or the German "economic miracle" (Wirtschaftswunder). Following long-standing debates on how to incorporate these guest-worker communities (as the expectation that they would return to their countries of origin did not materialize), Germany firmly rebranded itself as a "country of immigration" by the 2000s (Triadafilopoulos and Schönwälder 2006). This moniker gained increased importance in 2015, when Germany led the way in admitting almost one million refugees from Syria and elsewhere who had made their way to Europe.
At the same time, a state might engage in both emigration diplomacy in one context and immigration or transit migration diplomacy in another. One state that engages with such complex practices is Jordan. While precise data on intra-Arab migration flows is notoriously unreliable (Fargues 2014), it has been estimated that economic remittances from Jordanians working in oil-producing Arab states amounts to roughly 20 percent of the country's GDP (De Bel-Air, 2016). Understandably, Jordan has developed an emigration diplomacy framework in its bilateral workings with the Gulf Cooperation Council (GCC) states, paying particular attention to the well-being of its citizens abroad. At the same time, Jordan engaged in transit migration diplomacy with Egypt during the 1970s and 1980s when thousands of Egyptian workers needed to cross through Jordan in order to pursue employment in the GCC states (Brand 2013, 263). These bilateral negotiations focused on strengthening security, but also improving infrastructure and transport linkages between the two countries in order to facilitate transit flows. Finally, Jordan has become a destination of Palestinian refugees who settled in the country following major waves in 1948, 1967, and later, earning Jordan the opportunity to engage in negotiations with Israel from an immigration diplomacy perspective (Lukacs 1999).
More recently, as Syrians fled into Jordan since 2011, Amman's strategy has blurred the line between transit migration and immigration diplomacy as it agreed to host Syrian refugees in exchange for significant international aid. Negotiations culminated in the February 2016 Jordan Compact, an agreement drafted within the context of a London Pledging Summit (Mellinger and van Berlo 2016). Its main objective was the creation of 200,000 employment opportunities for Syrians within Jordan over a three-to five-year period. Jordan also agreed to lift regulatory barriers to allow refugees to work within the country and to lower work permit charges from 700 Jordanian dinars to 10 Jordanian dinars for those seeking lowskilled work. In return, $700 million in grants were raised with the expectation of additional pledges of $700 million in 2017 and 2018. At the same time, the World Bank adopted the Concessional Financing Facility, which, according to the Jordanian Minister of Planning and International Cooperation, awarded "$116.4 million in funding for Jordan" during 2016-2017 alone, "thereby leveraging some $670 million of concessional financing for development projects across a range of sectors" (World Bank 2017).

Issue Linkages and Types of Migration Diplomacy
The above examples show how migration diplomacy often relies on issue linkages and can be used as a means for states to pursue other goals, such as enhancing their security, achieving economic interests, or boosting their soft power via cultural or public diplomacy (Keohane and Nye 1977;Tollison and Willett 1979;Nye 2004) For example, Greenhill (2003) has shown that states can use threats of forced displacement as a form of coercive diplomacy in an effort to achieve their security aims, as when Milosevic threatened an outflow of refugees from Kosovo in 1999. Engaged in an asymmetric conflict with a much more powerful set of actors, the threat of ethnic cleansing of Kosovars was deployed by Milosevic as a means of exerting leverage over the NATO alliance. Oftentimes, weaker states are able to leverage their position as destinations of labor migration against stronger sending states as in the Middle East. In 2012 and 2013, elites in Jordan and Libya successfully elicited numerous policy concessions from Egypt by employing the expulsion of Egyptian immigrant laborers as leverage (Tsourapas 2018b).
States can also engage in migration diplomacy with other states in order to expel, deport, or transfer individuals or groups citing internal security concerns, as occurred in some historical cases of population transfers. Many such practices, oftentimes sanctioned by international organizations or colonial powers, have been accompanied by grave human rights abuses. The 1923 population exchange between Turkey and Greece was a condition of the Treaty of Lausanne following the dissolution of the Ottoman Empire. As a result, 1.5 million Greeks from Asia Minor, Eastern Thrace, the Pontic Alps, and the Caucasus were forcibly removed, as well as 400,000 Turks from Greece, according to a League of Nations plan that failed to avert a major humanitarian disaster (Shields 2016; Robson 2017). Migration diplomacy was similarly used for nation-building purposes in the 1947 Partition of India, where the forced displacement of more than 14 million people along religious lines accompanied the creation of the Republic of India and the Islamic Republic of Pakistan. There are also cases of migration diplomacy in which populations have been used as bargaining chips for weapons and military aid. For example, during peace negotiations in 1991 to end its civil war, Ethiopia sought arms and aid of $36 million from Israel before permitting the emigration of approximately 14,000 Ethiopian Jews in the "Operation Solomon" airlift (Brinkley 1991; see also Greenhill 2010, 315-316). In addition, migration diplomacy has been used by immigration states for security purposes when migration flows are viewed as conduits for terrorism or as strengthening organized crime. For example, bilateral extradition treaties are used as a means to remove individuals from a state's territory for perceived criminal or terrorist activities.
But states may equally use forms of migration diplomacy to achieve economic aims. Singapore, which hosts the largest share of migrants in Southeast Asia, has developed a migration diplomacy policy that allows the recruitment of foreign talent and foreign workers from abroad, as per its skilled and unskilled immigrant labor requirements (Hui 1997). Both bilateral agreements and memoranda of understandings on migration are diplomatic tools that states have frequently used to manage the cross-border flow of low-skilled labor (Wickramasekara 2015). Similarly, the 2016 EU-Turkey agreement and the Jordan Compact were both tied to the economic interests of Turkey and Jordan, respectively, with the latter providing Jordan economic benefits such as foreign direct investment (FDI) to special economic zones (SEZs) and tariff-and quota-free access to the single EU market for goods produced within SEZs by a labor force that is at least 15 percent Syrian (Mellinger and van Berlo 2016). More generally, European strategies of "externalizing" their migration control has led to numerous examples of migration diplomacy that involve a tit-for-tat exchange of cash for migration control. Senegal's negotiations with Spain are illustrative: "In exchange for joint patrols and repatriations, Spain promised money and favors" including a package of 20 million Euros of development aid in 2006 that coincided with the repatriation of Senegalese irregular migrants from the Spanish Canary Islands (Anderson 2014, 41-42).
Finally, states can use migration diplomacy to achieve public diplomacy aimsas a means of exercising soft power (Nye 2004), or for cultural or symbolic reasons (Koinova 2018;Koinova and Tsourapas 2018a). During the Cold War, for example, the United States differentiated between refugees and asylum-seekers from Communist and non-Communist countries, with refugees from the Soviet Union, Cuba, and elsewhere playing a valuable propaganda role. Another example, discussed above, is that of Egypt under Nasser subsidizing the emigration of highly skilled Egyptian workers as a means of boosting Egypt's role in the promotion of pan-Arabism across the Middle East (Tsourapas 2016). Brazil's approach to governing populations abroad reflects its wish to build a global role in international affairs (Margheritis 2017). The French state's export of teachers as part of the Organisation internationale de la Francophonie, or similar practices under the Japan Exchange and Teaching (JET) program, highlight the interaction between emigration and soft power. 8 One could argue that other programs such as the US Peace Corps or Fulbright Program are forms of state-sponsored temporary migration that are employed as a means of strengthening public diplomacy and promoting a state's soft power.

Migration Diplomacy Bargaining Strategies: Relative and Absolute Gains
Having discussed types of migration states and the linkages between migration diplomacy and security, economic, and other interests, we now turn to the bargaining strategies states use in migration diplomacy. As a first cut, we suggest the utility of examining strategies within a relative and absolute gains framework (Powell 1991). Similar to states' broader diplomatic efforts, we expect migration diplomacy to reflect two types of situations-zero-sum and positive-sum strategies. Originating from economics and game theory, zero-and positive-sum processes refer to an actor's rationale within a negotiations framework with regard to expected gains. Zero-sum perspectives are those of relative gain, where only one side is expected to benefit; the Arab-Israeli or the India-Pakistan conflicts, for instance, have long been perceived as functioning within a zero-sum mentality. "Better dead than red," Bertrand Russell's famous 1961 slogan, encapsulates a similar zero-sum attitude toward Cold War politics. Thus, a zero-sum rationale refers to the perception of the relevant stakes as relative gains, where one party measures success in relation to the (weakened) position of the other party. Within the migration diplomacy framework, such a thinking underlies Trump's campaign pledge to "build the wall" that aims to prevent further immigration from Mexico. In this case, one party views the management of cross-border population mobility with little regard to the other party's behavior and interests, thereby limiting prospects for cooperation.
In sharp contrast, positive-sum perspectives highlight mutual or absolute gains, where both sides are expected to benefit, albeit to different degrees. The negotiations around the creation of the European Coal and Steel Community, the precursor to the European Union, in the aftermath of World War II or, more recently, the creation of the North Atlantic Free Trade Agreement constitute examples of positive-sum approaches, which eventually led to or incorporated agreements of freedom of movement across national boundaries in ways that were designed to benefit all parties. Similar examples of positive-sum approaches to regional migration cooperation can be seen in other regional fora. In Africa, for example, both the Intergovernmental Authority on Development, which includes states from the Horn of Africa, Great Lakes Region and Upper Nile Valley, and the Economic Community of West African States have included migration components, including promoting freedom of movement-although it should be noted that such arrangements often also have an external component and have been heavily supported by actors such as the European Union and the International Organization for Migration.
While the degree to which each side benefitted might be different, the negotiating process in these cases was governed by an emphasis on absolute, rather than relative, gains. Thus, a positive-sum rationale focuses on absolute gains, expecting both parties to benefit, even if gains are not equally distributed between them. This logic usually characterizes bilateral agreements and memoranda of understanding on migration, as discussed above. Mexican migration diplomacy efforts aiming to revive the Bracero program were aimed at bilateral cooperation for mutual benefits, and West Germany's guest-worker program, which facilitated the immigration of Greek, Turkish, and other countries' laborers (or, gastarbeiter) into the country during the 1960s and 1970s, aimed to provide a solution to both West Germany's shortage of low-skilled labor, as well as the unemployment issues that plagued its partner-states (Hollifield 1992).
An example of immigration diplomacy constructed with the object of relative gains is the 1966 Cuban Adjustment Act, introduced under Johnson, which grants permanent residence status to any Cuban living in the United States for more than one year. The Cuban Adjustment Act was arguably shaped by Cold War politics and underlined the tense diplomatic relations between Washington and Havana at the time. It is not accidental that when bilateral relations between the two states showed signs of change after decades of tension, the President Bill Clinton administration extensively revised the policy in 1995. Similar relative-gains examples exist in the Arab world, where the oil-producing states belonging to the Gulf Cooperation Council host more than 16 million migrants. The 1990 Iraqi invasion of Kuwait was perceived as a security threat for GCC states, which employed their status as receiving states to engage in immigration diplomacy; when Yemen and PLO Chairman Yasser Arafat refused to denounce the Iraqi invasion, Saudi Arabia summarily deported more than one million Yemeni migrants. The same fate awaited almost the entire community of Palestinians working in Kuwait, numbering more than 400,000, who were also deported (Van Hear 1998, 80-86).
This is not to say that immigration diplomacy has not been concerned with absolute gains; similar to West Germany's gastarbeiter program and the Bracero program in the United States, Taiwan developed a guest-worker program in cooperation with Thailand, the Philippines, and Indonesia in the early 1990s. This program granted one-year visas to these countries' citizens working on Taiwan's construction, manufacturing, and services sectors. In the aftermath of the Cold War, Russia has at times afforded favorable immigration laws to immigrants from ex-Soviet republics that now belong to the Commonwealth of Independent States. Within the European context, the free circulation of people within the auspices of the EU single market was introduced as a win-win strategy for member states' economic development. In the Americas, the US H-2 visa program aims to recruit seasonal or temporary workers in cooperation with certain partner-countries. Similarly, the Canadian government's Seasonal Agricultural Workers Program, which it concluded following negotiations with Mexico and Caribbean countries, provides free housing and cooking facilities to seasonal workers from Mexico, while the Mexican government is responsible for their recruitment and negotiation of wages (Hennebry and Preibisch 2012).
Emigration diplomacy is also often perceived as a zero-sum game. The English crown, for instance, engaged in the early settlement of America from the seventeenth century onward partly due to its antagonism with France, Spain, and the Netherlands, all of which would also dispatch emigrants across the Atlantic. The early decades of the Arab-Israeli conflict had Arab states engage in emigration diplomacy as approximately 850,000 Mizrahi Jews resettled into the new state of Israel. Between 1949 and1950, Yemen had Israel airlift 49,000 Yemeni Jews in what is known as "Operation Flying Carpet." In August 1994, the Fidel Castro regime aimed to use emigration as a political weapon against the United States: it generated the balseros crisis that allowed more than 35,000 Cubans to flee the island heading for Florida over the course of a few weeks (Greenhill 2002, 51-60). More recently, following Gaddafi's example, the Tunisian President Zine el Abidine Ben Ali used emigration diplomacy to exploit European fears of radicalization via irregular immigration. Under his rule, the Tunisian state habitually aimed to extract political and economic benefits from EU states by threatening to relax border controls and allow local "terrorist" or "Islamist" elements into Europe (Natter 2015).
But sending states may also engage in emigration diplomacy aiming at positivesum gains scenarios. During the Cold War, such a strategy was part of authoritarian emigration states' soft power agenda (Tsourapas 2018a). For instance, a key Soviet Union strategy involved the short-term emigration of high-skilled Russian professionals across the Eastern bloc for the purposes of strengthening the two sides' political and developmental linkages (Babiracki 2015). Similarly, Bulgaria developed a scheme of dispatching professionals to Libya, as the two states shared an anti-Western ideological agenda and were able to mutually benefit from such mobility management agreements (Crampton 2007, 365). In the aftermath of the 1959 Cuban Revolution, the Castro regime organized the short-term emigration of thousands of medical professionals across Latin America, Africa, and Oceania as part of its "medical internationalism" (Huish and Kirk 2007;Blue 2010). The continuity in this policy was evident in Cuba's 2014 dispatch of doctors to Sierra Leone in the fight against Ebola (Jones 2014). Naturally, positive-sum gains in emigration diplomacy might also involve material benefits: in 2005, Fidel Castro signed an "oilfor-doctors" bilateral deal with Venezuelan President Hugo Chávez that would allow 30,000 Cuban doctors to staff the Venezuelan public health system in return for increased shipments of Venezuelan oil into Cuba (Feinsilver 2008, 216). Across all cases, emigration diplomacy was conceptualized as contributing to absolute gainswhile it produced key political and economic benefits for the sending states, it also generated important gains for host states.
Finally, transit states often assume a zero-sum mentality as per their transit migration diplomacy strategies. In the course of negotiations on resolving the Greek debt crisis, the Greek minister of defense frequently employed a relative gains argument: unless Europe provided a satisfactory solution, the Greek state would allow transit migrants to reach Berlin (Athens-Macedonian News Agency 2015). Libya's Qaddafi also resorted to coercive migration diplomacy when dealing with the European Union (Tsourapas 2017). At various times, he would demand European funding (from the European Union or individual member-states such as France or Italy) and threaten to "flood" Europe with African migrants. In a 2010 EU-Africa summit, Qaddafi stated that the cost of noncompliance, under Libya's coercive migration diplomacy, would be that "Europe will turn black" (Squires 2010). A few years before during a meeting of the African Union, Qaddafi declared, "[w]e will ask Europe to pay 10 billion euros per year if it really wants to stop migration toward Europe . . . Europeans who do not want to take the immigrants should either emigrate to American or pay Libya to keep its borders closed" (Greenhill 2010, 331).
But, similar to immigration and emigration diplomacy, examples of transit states aiming for absolute gains is not uncommon. This has already been explored in the cases of Jordan, which employed its status as a transit state in negotiations with Egypt, as well as in Mexican diplomacy vis-à-vis both the United States and a number of Central American governments. Such practices were also common during the Cold War, as Eastern bloc countries frequently coordinated their policies to enable transit migration. For instance, the 1949 defeat of the communist forces in the Greek Civil War led to the outmigration of more than 10,000 Greek political refugees. They were allowed to transit through Bulgaria and Yugoslavia unharmed and eventually settle in the Soviet Union and Czechoslovakia (Clogg 2013).
The point here is that states have at their disposal different strategies to engage in migration diplomacy, depending on a range of factors such as their foreign policy interests, bargaining power, the nature of the existing bilateral relationship between two states, and so forth. For example, Turkey's approach to migration diplomacy visà-vis European states has changed over time. During the 1960s and 1970s, Turkey pursued absolute gains via its signing of guest worker agreements with various European states, which served to reduce its unemployment and facilitate the flow of foreign exchange via remittances-all while also benefiting the economies of Western Europe. By 2015-2016 Turkey's relationship with European states had become more antagonistic as it attempted to leverage Europe's interest in stemming migration to secure substantial economic benefits (Greenhill 2016;Adamson 2018).

Conclusion
Migration diplomacy is a multifaceted process, both in terms of the actors involved and the strategies employed. As highlighted above, the identity of a sending, transit, or receiving state is neither singular nor static: some states may engage solely in emigration, immigration, or transit migration diplomacy policies, while others are able to employ multiple policies vis-à-vis a number of different actors at any one time. As states' interests evolve, or their position within the web of global migration flows changes, they may also revise their migration diplomacy accordingly-as the above example of changes over time in Turkey's strategy toward Europe illustrates. Migration diplomacy also involves linkages with other areas of states interests, including national and domestic security concerns, economic interests, and interests in promoting public diplomacy or other forms of enhancing a state's soft power. In terms of strategies, migration diplomacy can be approached as a zero-sum game by pursuing relative gains or as a positive-sum game in order to reach mutually beneficial outcomes.
In this article we have presented a basic framework for thinking about the relationship between cross-border mobility, state power and interests, and interstate bargaining and diplomacy. We have proposed a definition of and delineated the scope conditions for what constitutes migration diplomacy, as well as laying the groundwork for future theorizing and empirical study. As such, the interests, linkages, and strategies identified here are not meant to be exhaustive but rather illustrative. Further research is needed to identify the universe of cases that could be characterized as instances of migration diplomacy and to map out the diverse actors, interests, and processes that are engaged in pursuing immigration, emigration, and transit migration diplomacy. In this regard, a key area for future research would be the conditions under which the migration diplomacy strategies of states are more or less effective. Clearly, a number of factors, including the differential levels of power and resources available to state actors, are areas that merit further examination. Finally, an additional set of questions that merits further research concerns the different mechanisms at play in instances of migration diplomacy. How applicable is a two-level game theory approach, for instance, in understanding international agreements on migration flows, and to what extent do sending, transit, and receiving states differ with regard to the mechanisms they use? Under what conditions are states most likely to achieve their aims? And what are the determining factors that lead to zero-sum versus positive-sum approaches to interstate bargaining on migration issues? These are all important questions not just for theory, but also for formulating policies to address the migration issues that are increasingly at the forefront of the international political agenda.
The concept of migration diplomacy serves to highlight the multiple effects of cross-border population mobility-not merely on numerous aspects of domestic politics but also on states' international relations. There is a well-developed literature in political science and sociology on the domestic impacts of migration on states and on the evolution of state migration control and migrant integration policies. Yet, there is less understanding of the relationship between cross-border flows of people and the national interests and diplomatic strategies of states. Given the likelihood that migration will only increase in its importance to states and their policymakers in the next decades, there is plenty of room for further research on the international politics of global migration and mobility.