U.S., NATO and Arab League war planes were used for most of the intervention mission in Libya. But such aerial bombing campaigns work better in a nation like Libya, where major city areas are spread out. That's not the case in Syria. What's more, Syria has a larger and more advanced arsenal of anti-aircraft weaponry, Exum said, that would have to be taken out before a sustained bombing campaign could even begin. "That in itself would be a major undertaking," he said.
Syria is located in one of the most tense parts of the world, with Lebanon and Israel to the south and Turkey and Iraq to its north and east. That would put U.S. and NATO forces and aircraft in potentially deadly situations the president and other Western leaders want to avoid.
Intervention could spawn a sectarian civil war. If American and NATO forces were to oust Assad, "that could make things worse, and lead to a civil war" among Syria's religious groups, O'Hanlon said. That would mean "a long operation" for American troops-just as the Iraq war-which stretched on and on due largely to fighting between religious sects. Some experts, like Patrick and Bennett, have predicted a Syrian civil war might "boil over" and send ripple waves across the already volatile region. "If the unrest in Syria boils over, the consequences would be significant," the CFR scholars wrote. "The nation borders Israel, Iraq and Jordan, NATO ally Turkey, and finally Lebanon, which could see its precarious stability threatened by civil war in Syria." Obama and his national security advisers surely are aware of this likely outcome, and will seek to avoid placing American troops on the ground, only to be caught up in a deadly sectarian struggle.
"It's not true that Syria hasn't had a history of sectarian tensions," Exum said. "A lot of things that should have worried us about Iraq should worry us about a military intervention into Syria."