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,