The Assad government in Syria is facing tough opposition from rebels who have been joined by militants from other countries. These foreign fighters provide firepower to the rebels but experts say they may fight in other countries after the civil war in Syria is over.
Crossing borders to fight alongside local militants is not new. The Soviet Union faced foreign fighters in Afghanistan in the 1980s, and more recently, the U.S. faced them in Iraq.
Former CIA official Paul Pillar says the foreign fighters in Syria may eventually cause instability in other parts of the region and the world.
"You look at the war in Afghanistan against the Soviets, which went on about a decade. That spawned militants and militant groups that went on to be active in many different places around the world. So there’s no reason to expect that Syria is going to be anything different. We have people, militants who acquire skills, acquire inspiration, acquire some organization, and that’s not going to go away once the dust settles in Syria," said Pillar.
Pillar says in many instances, people joining conflicts like the one in Syria may not have been militant before, but once they become battle-hardened, they can cause instability in their own countries.
"This is something that, for example, Saudi officials have worried about for a long time, as well as the other Gulf Arab countries, where they have had their own nationals go to fight in places like Iraq, Afghanistan and now some of them in Syria," he said.
The 1996 bombing of Khobar Towers in Saudi Arabia, with 19 US serviceman killed, is often cited as an example of how those inspired by foreign fighters have carried out terror attacks in their own countries.
Analysts say Syria is providing the opportunity now for mostly Sunni Muslims to go abroad and fight. Stephen Tankel is a counterterrorism expert at American University in Washington.
"This is one of the reasons, quite frankly, that the U.S. is reluctant to become involved in Syria along with a host of others, is that you’ve already got an open front, but the U.S. presence could draw even more groups to that front," said Tankel.
There is also the issue of who to arm among the anti-Assad forces. Stephen Tankel says the options are limited.
"The Obama administration is seeking ways to support the rebels who are not al-Qaida. And that is a process that has been ongoing, looking at how they can get weapons into the hands of those whom they want to support and keep them out of the hands of those they don’t. Of course, there’s only so many steps you can take, and once those weapons get onto the battlefield, it becomes much more difficult to control them," he said.
While the international community is focused on finding a political solution to the war in Syria, experts in Washington believe officials should be working on plans to deal with the armed groups once the conflict is over.