Migrants and refugees beg Macedonian policemen to allow passage to cross the border from Greece into Macedonia during a rainstorm, near the Greek village of Idomeni, September 10, 2015.
Migrants and refugees beg Macedonian policemen to allow passage to cross the border from Greece into Macedonia during a rainstorm, near the Greek village of Idomeni, September 10, 2015.
Yannis Behrakis / Reuters

In recent weeks, several leading Republican presidential candidates have argued in favor of selectively sealing U.S. borders to Syrians and others. That—and the discontinuation of any Syrian refugee resettlement programs—they argue, will keep the United States safe from terrorist attacks. Such fantastical and ill-informed suggestions are counterproductive on their own terms, but they also distract from very real and consequential ways in which refugees and migrants are being used as political and military weapons.


All sides in the Syrian civil war have, to some extent, strategically engineered mass movements of civilians into and away from their areas of territorial control. In some cases, the systemic depopulation and repopulation of territory represent attempts to gain tactical military advantage. For example, in early October Amnesty International reported that the Democratic Union Party (PYD), a Kurdish rebel group in Syria, was demolishing homes and displacing entire villages in order to, as Mao would have put it, “drain the sea [the civilians] in which the fish [the enemy] swims.” The PYD is not alone. This kind of engineered migration has long been a tool of warfare, since noncombatants can provide safety, succor, and support and serve as a source of recruits.

Conversely, civilians may also be prohibited from fleeing areas controlled by combatants, in order to shield soldiers and their supporters from military attack. Human Rights Watch reported in early November, for instance, that the rebel group Jaysh al-Islam has been keeping civilian hostages in northern Syria in order to deter attacks by government forces.

People take part in an anti-Donald Trump, pro-immigration protest outside the Plaza Hotel, where U.S. Republican presidential candidate Donald Trump spoke, in the Manhattan borough of New York December 11, 2015. Trump vowed to close the borders to Muslims
People take part in an anti-Donald Trump, pro-immigration protest outside the Plaza Hotel, where U.S. Republican presidential candidate Donald Trump spoke, in the Manhattan borough of New York December 11, 2015. Trump vowed to close the borders to Muslims.
Brendan McDermid / Reuters
In other cases, such demographic reengineering schemes appear to be longer-term bids to maintain or secure postwar control of particular pieces of Syrian real estate, through a strategy I have called “dispossessive engineered migration,” a subset of which is ethnic cleansing. It has been reported, for instance, that forces loyal to Syrian President Bashar al-Assad have been selectively cleansing neighborhoods under their control and repopulating them with regime allies, some of whom are internally displaced people from elsewhere in Syria. Likewise, as War on the Rocks reported last week, the self-proclaimed Islamic State (also known as ISIS) has routinely used violence to encourage “infidels” to flee their lands and then offered their property and assets to incoming loyalists. This strategy of seizure and appropriation through forced migration, too, has a long and rather sordid history.

But the weaponization of displaced people is not limited to conflict zones; migrants and refugees may also be used for influence far from the battlefield. For instance, during the first week of November, Jamal Zubia, spokesman for the National Salvation Government of Libya's General National Congress—one of the two rival governments in Libya—issued a lightly veiled threat against the European Union: if not offered diplomatic recognition and financial assistance, it might actively assist migrants and asylum seekers in their bids to reach Europe. In an interview with The Telegraph, Zubia emphasized that although his Tripoli-based faction was not planning to follow through on its threat imminently, it might well do so in future: “We are protecting the gates of Europe, yet Europe does not recognize us and does not want to recognize us. So why should we stop the migrants here? . . . It is a strategic threat, yes, but I would not rule out us doing it one day.”

The Libyan warning came close on the heels of analogous threats that Turkey reportedly made in September and October (and possibly earlier). According to The Wall Street Journal, Reuters, and other sources, Turkish demands on Europe included financial aid to mitigate the significant burden of hosting more than two million Syrians, the lifting of EU-related visa restrictions on Turkish travelers, and the reinvigoration of Turkey’s EU membership bid. By some accounts, Ankara also renewed an earlier demand for the creation of a “safe zone” along the Syrian border.

In both the Libyan and Turkish cases, the underlying message was clear: concede to our demands or face (possibly severe) migration-related consequences. Although the Libyan threat apparently remains latent for the moment, a number of Turkish demands have already been met, including an initial three billion euros in aid and the resuscitation of Ankara’s EU membership bid, according to The New York Times, the BBC, and other sources.

Using migration as an instrument of state-level coercion is nothing new. Since the 1951 Refugee Convention came into force, there have been at least 75 attempts by state and nonstate actors to use displaced people as means to political, military, and economic ends. Coercers’ demands have ranged from the simple provision of financial aid to requests for full-scale invasion and assistance in effecting regime change. Such was the case when the exiled Haitian President Jean-Bertrand Aristide used the threat of a flood of Haitian boat people into the United States to persuade the administration of U.S. President Bill Clinton to oust the sitting junta and restore him to power in September 1994.

Likewise, former Libyan leader Muammar al-Qaddafi rather dramatically promised to “turn Europe black” if the EU failed to meet his demands. Although his objectives varied widely over time—and ranged from the lifting of sanctions to the provision of billions of euros in aid to the quashing of support for protesters in the early days of what became the Libyan uprising—Qaddafi used this tool with varying degrees of success in 2004, 2006, 2008, and 2010, before fatally overplaying his hand in 2011.

In nearly three-quarters of the historical cases, the coercers achieved at least some of their objectives. In well over half of the documented cases, they obtained all or nearly all of what they sought, which makes this tactic more effective, albeit harder to successfully manage and control, than either economic sanctions or traditional, military-backed coercive diplomacy.

Even more striking, some threats to deploy refugees and migrants as weapons have actually been carried out. In the spring of 1999, then Yugoslav President Slobodan Milosevic initially threatened and later expelled hundreds of thousands of Kosovars in an attempt first to deter NATO from launching a bombing campaign during the Kosovo war and then to compel the alliance into ceasing it. Former German Foreign Minister Joschka Fischer later admitted his regret in not taking Milosevic seriously when he said that he “could empty Kosovo in a week.”

Former Cuban President Fidel Castro also used migration as a weapon against the United States on at least three occasions: in 1965, in 1994, and, most famously, during the Mariel boatlift of 1980. As with Qaddafi, Castro’s objectives and demands varied over time but included, among other things, a significant shift in US policy toward Cuban hijackers and the regularization of U.S.-Cuban immigration.


Despite its prevalence, this kind of coercion has historically been underreported. For one thing, coercive threats are often issued privately and bilaterally; in many cases, neither coercers nor their targets have incentives to reveal the political blackmail. For another, this kind of coercion is sometimes intertwined with other political considerations. For example, Ugandan leader Idi Amin expelled most Asians from his country in 1972, in what has commonly been interpreted as a naked asset grab, since Asians owned most of the big businesses in Uganda during that period. Far less noted is the fact that approximately 50,000 of those who were pushed out held British passports and that these expulsions happened at the same time Amin was demanding that the British halt a planned drawdown of military assistance to his country. Amin even announced his intention to foist 50,000 refugees on the British, with a convenient 90-day grace period for the country to reconsider its decision on military aid.

As in the Ugandan case, the vast majority of known targets of this kind of coercion have been liberal democracies (over 70 percent); another 11 percent have been groups of countries that have included liberal democracies. This is no accident. Liberal democracies tend to be particularly vulnerable because they find themselves trapped between conflicting imperatives. On the one hand, such states generally have made normative and legal commitments to protect those fleeing violence and persecution. On the other, as recent events in Europe and the United States make clear, some segments of democratic polities are strenuously opposed to accepting displaced people, whether for rational economic, political, or cultural reasons or for irrational, xenophobic ones. Because targets cannot simultaneously embrace a given group of migrants and reject them, the incentives to concede to coercers’ demands and make the problem disappear can be compelling.

So what options do potential targets of migration-driven coercion have? There are several, but none is a silver bullet; each has advantages and drawbacks. Targets can concede, but this carries the risk that coercers may repeat and escalate their demands, as Qaddafi did in the 2000s. Alternatively, targets can take military action to change conditions on the ground in countries of origin. But wars are costly and their outcomes uncertain. Again, the Qaddafi example is instructive: the threat of Libyan coercion did not disappear when he did, and subsequent instability in the country and the region does not inspire confidence about the option of regime change.

Alternatively, target governments can appeal to their populations to welcome the displaced, emphasizing the long-term economic virtues of migration, particularly for countries suffering declining birthrates and shrinking tax bases. If this strategy succeeds, coercion becomes impossible because threats of “flooding” will, in theory, be met with a shrug. But this kind of attitude change tends to be the result of a long-term campaign. The strategy is generally not effective in the midst of an ongoing migration emergency. And it would be particularly challenging in the wake of the attacks in Paris, in light of the fact that at least one of the ISIS-aligned attackers traveled to Europe in the midst of a stream of displaced people. 

Finally, and conversely, targeted states can abrogate their commitments, close their borders, and lock their doors. This, too, makes successful migration-driven coercion difficult, if not impossible. However, such a stance often encourages others to follow suit and would represent an abandonment of key components of liberal democracies’ most enviable values. In the end, the long-term costs to liberal morals, philosophy, and identity may be far greater than any short-term humanitarian- and assimilation-related costs that come from accepting migrants and refugees, the real victims of this kind of coercion. Such an approach is also very unlikely to solve migration-related security concerns. Indeed, sealing the borders to migrants and refugees may ironically help feed jihadist narratives, which in turn may sow the seeds for a different kind of weaponization of the displaced.

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  • KELLY M. GREENHILL is an Associate Professor of Political Science and International Relations at Tufts University and a Research Fellow in the International Security Program at the Belfer Center of Harvard University’s Kennedy School of Government. This piece draws in part from her book Weapons of Mass Migration: Forced Displacement, Coercion, and Foreign Policy (Ithaca, NY: Cornell Studies in Security Affairs, 2010 and 2016).
  • More By Kelly M. Greenhill