The challenge facing President Barack Obama and his political and military advisers is this: How to "punish" the regime of President Bashar al-Assad for its alleged use of chemical weapons on civilians, but not punish it too severely, lest that destroy a government whose survival is deemed preferable, for U.S. regional interests, to one led by the most radical rebel elements.

While the administration appeared to be gearing up this week for some form of military response to an incident denounced by Secretary of State John Kerry on Monday as a "moral obscenity," White House Press Secretary Jay Carney told reporters Tuesday that the purpose of any intervention was not to oust Assad. "It is not our policy to respond to this transgression with regime change," he said. "That is not what we are contemplating here."

The policy, according to Mark Perry, a foreign policy analyst and author of several books on military history, can be translated as follows: "The U.S. would like to see Bashar al-Assad lose, but they don't want to see the opposition win -- but how do you do that?"

"It's not sound military doctrine," Perry said. "We don't usually deploy to 'punish' but to 'defeat.' What's the goal here?"

Beyond that overall strategic question, Obama must decide how many targets and how often should they be struck -- what's too much or too little. And then there's the question of whether any punishment action by the U.S. and coalition partners deters Assad from using chemical weapons, or instead emboldens him. That's a multi-faceted dilemma for a president still trying to extricate troops from more than 10 years of war in Afghanistan.

The Pentagon has left no doubt that it's leery of getting involved in Syria. In July, Gen. Martin Dempsey, Chairman of the Joint Chiefs of Staff, delivered an assessment of military options to Sen. Carl Levin, head of the Armed Services Committee, in which he discussed possibilities that included "limited stand-off strikes."