Iran enhanced role

"... Iran cannot rule out the possibility that even limited U.S. action will weaken the regime. Nor can it conclude that Washington does not intend to conduct a more extensive, less symbolic air campaign against al Assad. But it can, however, prepare for either outcome. Strategists in Tehran know that the Americans have air superiority, but they know Iran has the advantage on the ground in Syria, Lebanon and Iraq.

Iran is thus positioned to foment an insurgency. (And the U.S. invasion of Iraq enhanced Iran's experience in fomenting insurgencies.) Any insurgency would worsen sectarian tensions in Syria and throughout the region, in turn further radicalizing Sunni militias. Jihadists gaining ground would force the United States to work with Tehran to contain Sunni radicalism.

In the unlikely scenario that the United States becomes embroiled in another major war, extricating itself from that war would necessarily require Iran's cooperation. But what really gives Iran leverage is the fact that since 9/11, jihadists and Islamist groups have had the opportunity to gain power when Arab regimes collapse..."