To many observers, the estimated 11,000 foreign fighters who have poured into Syria during its civil war are worrying signs of a growing trend toward transnational conflicts. And, in one sense, they are right. Since 2001, as many as 20,000 outside insurgents, mostly jihadis, have moved into war zones from Afghanistan to Iraq and Nigeria either to join local rebel groups or to establish footholds for al Qaeda and other Islamist organizations. In the last decade, governments have spent hundreds of billions of dollars attempting to contain the roaming combatants, and hundreds of millions more trying to reintegrate them back into their home countries.
In another sense, however, observers are wrong. Foreign fighters might seem to be characteristic of twenty-first-century warfare, but, in fact, they are nothing new. Over the past two centuries, more than 70 insurgencies have successfully gone transnational; there have been foreign fighters in at least one in five modern civil wars. The list includes Lord Byron and his London Philhellenic Committee, which aided the Greeks in their war for independence from the Ottoman Empire in the 1820s, the ragtag volunteers who joined Sam Houston’s army in the 1836 Texas War of Independence, the Communist International–directed coalition of leftists supporting the Republican faction and the Irish Catholic anticommunists who backed the nationalists in the Spanish Civil War in 1936–39, and Jewish paramilitary groups who battled in the 1948 Israeli War of Independence.
As in decades past, foreign fighters have been involved in more recent conflicts around the world. Everyone knows about their presence in the Middle East, but there are others. In the late 1990s, 200 Albanian-Americans fought alongside the Kosovo Liberation Army. A few years later, members of the Irish Republican Army fled Colombia after they were arrested on charges of training rebels in the Revolutionary Armed Forces of Colombia (FARC). And today, several thousand foreign combatants, constituting what the United Nations has termed an “insurgent diaspora,” are spread across the African Great Lakes region, some tied to the Lord’s Resistance Army, others from Rwandan rebel groups.
Although transnational insurgencies comprise highly diverse groups across different conflicts and eras, they still have much in common. For one, such forces are winning: transnational insurgencies have won nearly half of the civil wars in which they have fought, almost twice the success rate of insurgencies overall. Several Israeli prime ministers have acknowledged that Israel’s victory in 1948 relied on the World War II veterans who aided the fledgling state against Arab armies. In other conflicts throughout history, prominent foreign fighters were either instrumental in extending insurgencies or making them costlier to suppress: the Marquis de Lafayette, the French general who fought for the American rebels during the Revolutionary War; the Italian general Giuseppe Garibaldi, who supported the Republican uprising in Brazil in the 1830s; and Abu Musab al-Zarqawi, who formed al Qaeda in Iraq under the U.S. occupation. The patterns of recruitment for such disparate fighters are broadly similar and, because of that, they all have the same Achilles’ heel.
Insurgent groups, from the Texian Army in 1836 to al Qaeda affiliates in Syria today, use despair rather than optimism to recruit members. Generally, they tell recruits that they are losing a war of survival and that they face an existential threat. It might not seem like the most persuasive pitch, particularly for fighters who, if they join, must violate a number of laws and take up arms in an unfamiliar territory. But it works. Such groups can convince a recruit that he or she is part of an endangered community and is obliged to defend it. The strategy works best with foreign recruits who share the movement’s ideology, ethnicity, or religion but who, unlike local fighters, do not have immediate communities and families in the line of fire.
But recruiters can also add volunteers who are only loosely affiliated with, or are merely sympathetic to, a certain group. Such fighters are often persuadable because of their weak affiliations with their own country and national identity, especially in the case of unassimilated immigrants or the politically repressed or economically marginalized. Many transnational insurgencies have typically preferred to bring these more pliable foreign foot soldiers on whenever possible, rather than risk their own regular members on the battlefield. This strategy appears to work well in ideological conflicts, but it is more difficult for ethnic rebel groups to sustain. In fact, even the most successful ethno-nationalist insurgencies have tended not to use foreign fighters. The Tamil Tigers in Sri Lanka and the Kurdistan Workers’ Party in Turkey were successful at raising foreign financial support, but they apparently did not aim for more than that. They imported guns, not sons, perhaps because they could never make a credible claim that their struggle represented enough of an existential threat to rouse members of their far-flung diaspora to come and join them.
In cases where foreign fighters have successfully been recruited on such grounds, such as Afghanistan and Iraq, the propaganda produces its own problems. In these conflicts, the foreign fighters, driven by the belief that they are fighting a desperate battle to the end, act more aggressively than local insurgents -- even when their side is actually winning. It’s no accident that most suicide missions in Afghanistan and Iraq were carried out by foreign fighters rather than local militants. Fighting for what is often an abstract ideal, without having to worry about direct retaliation against their families, the foreign fighters need not show mercy. Some insurgent groups, such as the Islamic State of Iraq and al-Sham (ISIS) and Jabhat al-Nusra in Syria, have taken advantage of this dynamic by using foreigners to target civilians when the local combatants will not.
Differences between foreign and local insurgents can sow discord among them. The past decade has provided ample evidence that employing foreign fighters offers as many drawbacks as benefits. In Iraq, the spike in sectarian violence perpetrated by al Qaeda–linked, foreign-dominated militants led local Sunni insurgents to turn against them and band together in the so-called Awakening movement, on the side of coalition forces. In Afghanistan, a group of locals in the town of Gizab, who were intent on driving the Taliban from their province, allied with U.S. soldiers, who called them the “Good Guys of Gizab.” In Somalia’s civil war, the indigenous Somali leadership of the Islamist group al Shabaab turned against the Western jihadis in the group for purportedly failing to champion local rebel interests, favoring instead the most aggressive views of al Qaeda. Most recently, in Syria, ISIS and Jabhat al-Nusra have devoted at least as much energy to battling local rebels of the Free Syrian Army -- and each other -- as they have the regime of Bashar al-Assad.
Loyalty is another problem. Although some foreign recruits remain loyal to their cause their whole lives, inevitable stories of disaffected fighters can make it difficult for insurgent leaders to retain their core supporters. Often, after an early spike of interest, the tide of volunteers in a transnational insurgency ebbs with reports of low morale and ungrateful civilians. It often surges again after major battles, or outright victory, when those not committed enough to risk their lives finally arrive to try to claim some of the victory. In 1980s Afghanistan, for example, Osama bin Laden never had more than a couple hundred volunteers to fight the Soviet Union, but their ranks swelled by more than 10,000 once the Red Army had withdrawn.
Historically, most foreign fighters have not stayed around even in cases in which ethnic or national groups won hard-fought sovereignty, such as the Texas Revolution, in which some Mexicans and European immigrants enlisted in the Texian Army. And when former combatants have returned home, intelligence services have usually kept a close watch on them. In the Spanish Civil War, veterans of the Abraham Lincoln Brigade -- the name given to the nearly 3,000 U.S. volunteers who fought for the Republican side -- were among the only Americans with combat experience when World War II began. But they were barred from joining the U.S. military. Yet, for the most part, foreign fighters were granted amnesty by their own governments. The vast majority of them went on to lead essentially ordinary lives, even if they remained active in radical politics or sectarian or diaspora communities.
It became harder for foreign fighters to return to their homes about 25 years ago, when the Arab mujahideen fighting the Soviet occupation of Afghanistan formed al Qaeda. Although the fighters felt confident that they had defeated the Red Army and hastened the collapse of a superpower, they knew that their Arab governments, which viewed them as domestic threats, would not allow them to move back. As a result, they became stateless and truly transnational, using their networks to move into conflict zones from Bosnia to the Philippines. They made their appeals global as well, speaking of a worldwide Muslim community engaged in a fight for its survival against Western-led domination. They succeeded in framing every subsequent conflict that they joined as a single front in this greater war.
Syria has changed that jihadi narrative somewhat, from the established line of defending Muslims against Western powers to one of saving fellow Sunnis from Assad’s Alawite regime, which is supported by Shiite Hezbollah and Iran. The foreign fighters who joined the fray in Damascus about a year after the uprising began had prior experience with waging this kind of sectarian conflict in Iraq; they immediately introduced brutal tactics, including suicide bombings and beheadings. In response, as many as 5,000 Hezbollah fighters, along with other foreign Shiite militants, have taken up arms in support of the Syrian army.