Experts warn Syrian rebel victory poses 'wildly complex' national security threat: 'Who knows what's next?'

Syria's future remains unclear after Islamist rebels toppled the Assad regime, seizing control of Damascus and driving the Syrian dictator out of the country. 

Foreign policy experts and officials alike reacted to the news on Sunday, speculating about what might be in store for the Middle East nation and the American forces residing there.

"Who knows what's next?" former Deputy National Security Adviser K.T. McFarland asked. 

McFarland joined "Fox & Friends Weekend" to discuss the unrest. Like others, she suggested the change paints an uncertain picture.

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"[Bashar Assad] was weak and incompetent, and he was propped up in governance in Syria by Iran and by Russia, by Russian forces, by Russian military equipment, by, in some sense, Iran's money, but they're preoccupied now… Iran is preoccupied because of what Israel did to Iran and Hezbollah and Russia is preoccupied because of Ukraine and a faltering economy, so those two guys propping up Assad, they're not, they were propping him up as well," she said.

"But the [multiple] rebel groups got together, and they saw a moment of opportunity, and they moved into Syria… and President Trump is so right to say, ‘let it play out. This is not our fight.’ I'm just sorry we have 900 American forces in that country because who knows? Are they sitting targets? Are they potential hostages? What's their role going to be? We don't know."

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Sen. Marsha Blackburn, R-Tenn., also weighed in on Sunday, offering a message of caution and concern.

"We have to realize there are no good guys in this. These rebels are connected to al-Qaeda. We know that Iran is going to lose supply lines to Hezbollah. We know that Russia is losing access to a warm weather port, and we need to make certain that we support Israel," she said.

Dan Hoffman, former CIA station chief, warned that the development poses a "widely complex challenge" to U.S. national security that awaits the Trump administration when the president-elect assumes office next month.

"The concern I think that we would have going forward is the potential for a power vacuum here. We saw this in Iraq and in Libya and terrorists take advantage of that, and the concern I think we have is that potentially terrorists may be flocking to Syria right now, seeking to take advantage of just that," he explained. 

"We also have a real challenge there because state actors like Russia and Iran, formerly allied with Syria. Remember, Russia has a naval base in Tartus. They are not going to be on the side of solving this problem with us. We've got real challenges with them as well, so gaining some kind of international consensus on the way forward is also a major challenge."

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President-elect Donald Trump also weighed in shortly after the news broke, posting on Truth Social.

"Assad is gone," he wrote. "He has fled his country. His protector, Russia, Russia, Russia, led by Vladimir Putin, was not interested in protecting him any longer. There was no reason for Russia to be there in the first place. They lost all interest in Syria because of Ukraine, where close to 600,000 Russian soldiers lay wounded or dead, in a war that should never have started, and could go on forever."

"Russia and Iran are in a weakened state right now, one because of Ukraine and a bad economy, the other because of Israel and its fighting success," h econtinued. "Likewise, Zelenskyy and Ukraine would like to make a deal and stop the madness. They have ridiculously lost 400,000 soldiers, and many more civilians. There should be an immediate ceasefire and negotiations should begin."