3. Limited U.S. military aid tips the balance in favor of the rebels, Al Qaeda-allied groups emerge more powerful than before.

Part of the conundrum for Obama as he gets the U.S. involved in Syria is that some of the rebels the U.S. is backing are allied with groups tied to Al Qaeda. So even if U.S. aid helps topple Assad, the U.S. could face a worse outcome: radical jihadists empowered and emboldened in the region. That is the kind of mixed blessing the U.S. got backing the Taliban against the Soviet Union in Afghanistan in the late 1970s and early 1980s. It’s a primary reason Obama is limiting the kind of military aid he is sending to the rebels.