The Syrian civil war has gone from bad to worse, with casualties mounting and horrors multiplying. Civil wars like Syria's are obviously tragedies for the countries they consume, but they can also be catastrophes for their neighbors. Long-lasting and bloody civil wars often overflow their borders, spreading war and misery.
In 2006, as Iraq spiraled downward into the depths of intercommunal carnage, we conducted a study of spillover from recent civil wars in the Balkans, the Middle East, Africa, and elsewhere in order to identify patterns in how conflicts spread across borders. Since then, Iraq itself, along with Afghanistan, Libya, and Yemen, have furnished additional examples of how dangerous spillover can be. For instance, weapons from Libya have empowered fighters in Mali who have seized large swathes of that country, while al Qaeda-linked terrorists exploiting the chaos in Yemen launched nearly successful terrorist attacks on the United States.
Spillover is once again in the news as the conflict in Syria evinces the same dangerous patterns. Thousands of refugees are streaming across the border into Turkey as Ankara looks warily at Kurdish groups using Northern Syria for safe haven. Growing refugee communities are causing strain in Jordan and Lebanon. Meanwhile, the capture of 48 Iranians, who may be paramilitary specialists, could pull Tehran further into the conflict. Israel eyes developments in Syria warily, remembering repeated wars and concern over the country's massive chemical weapons arsenal. For the United States, these developments are particularly important because spillover from the civil war could threaten America's vital interests far more than a war contained within Syria's borders.
Of course, much will depend on how exactly this spillover plays out -- and certainly no one yet knows what will happen in the wildly unpredictable war for control of Syria. But if past informs present, the intensity of the war effect typically correlates strongly to the intensity of the spillover, often with devastating consequences. At their worst, civil wars in one country can cause civil wars in neighboring states or can metastasize into regional war. And it's the severity of the spillover that should dictate the appropriate response.
There are five archetypal patterns of spillover from civil wars.
Refugees: Spillover often starts with refugees. Whenever there is conflict, civilians flee to safety. The sad truth about civil wars is that often civilians are targets: Without clear front lines and when "enemy combatants" can be any young male who can pick up a gun, the danger is clear. So the goal of the warring armies is often to kill as many of the other side's civilians as possible or at least drive them from their homes. To avoid the rapine and economic devastation that accompany these kinds of conflicts, whole communities often flee to a foreign country or become displaced within their borders, as more than a million Syrians have.
In addition to their own misery, refugees can create serious -- even devastating -- problems for the nations hosting them. The plight of Palestinian refugees and their impact on Egypt, Jordan, Lebanon, and Syria since 1948 is a case in point, contributing to instability in their host countries, international terrorism, and wars between Israel and its neighbors.
Beyond this, refugees can often become carriers of conflict. Angry and demoralized refugee populations represent ideal recruitment pools for the warring armies; the Taliban have drawn from angry young Afghan refugees raised in Pakistan, offering them a chance for vengeance and power. Indeed, refugee camps frequently become bases to rest, plan, and stage combat operations back into the country from which the refugees fled. For instance, the camps set up in the Democratic Republic of Congo after Rwanda's genocide quickly became a base of operations for fleeing Hutu rebels to regroup.