There is also the matter of Syria's air defenses, which are largely intact even after 3 years of civil war, and the unknown air defense capability of ISIS:

"Flying aircraft over Syria is very different than in Iraq," said Eric Thompson, senior strategic studies analyst at the Center for Naval Analyses, which advises the U.S. military as part of the CNA Corp think tank in Virginia. "There are more sophisticated air defenses, some in the hands of ISIS,” he added, using an alternative name for Islamic State.

In a recent report, Small Arms Survey, an independent research group based in Geneva, detailed a range of shoulder-launched missile systems in the hands of the militants. Known as MANPAD, or man-portable air defense systems, some were apparently stolen from government stockpiles while others were supplied from outside sources in other countries.

But in the end, the major obstacle, as Kaplan mentions, is a lack of actionable intelligence. Who do we bomb? Where?

The Pentagon has publicly conceded it has less-than-perfect information about the movements and capabilities of Islamic State fighters, a limitation reflected in a failed attempt by U.S. special forces to rescue Foley in July.

Intelligence gaps raise the risk of civilian casualties from any U.S. air strikes in Syria, especially given that the militants are highly mobile and intermingle with the civilian population in urban areas like Raqqa.

From unmanned armed drones to powerful Stealth bombers, a wide range of U.S. airpower is at Obama’s disposal, including possible missiles fired from warships at sea or from aircraft flying outside Syria’s borders.

Drones, Obama’s weapon of choice in the fight against al Qaeda in Pakistan and Yemen, could also be used, but possibly more for surveillance than missile strikes. Given the risk of missed targets and civilian casualties, U.S. forces typically prefer to operate drones in tandem with intelligence operatives on the ground.

Islamic State leaders' use of encryption in communications is highly sophisticated and hinders efforts to track them, according to U.S. officials familiar with the group’s tactics. As a result, Islamic State leaders such as Abu Bakr al-Baghdadi are expected to be hard to find.

It may be, as Joint Chiefs Chairman General Dempsey says, that in order to take on Islamic State, we are going to have to fight them in Syria. But we shouldn't go off half cocked in doing it. Building up intelligence assets will take time - if it can be done at all, given the fractured nature of the Syrian opposition.

But time is the one commodity in short supply. ISIS is shredding the Syrian army in its drive to create an independent state and grows stronger by the week. US choices are narrowing as a result. A Syrian operation carries with it great risk and you have to wonder if our risk-averse president is up to the challenge.