Wanted: Better War Planning by Better War Planners

Who reads passages like the following from this news report  on the American decision to arm rebels in Syria, and feels comforted?

“Arming the Syrian rebels is unlikely to tip the balance in their favor,” said Shadi Hamid, director of research at the Brookings Institution’s Doha Center. “It might have made a difference a year ago, but, today, the Assad regime -- particularly after re-taking Qusair -- has the advantage.”

Even some U.S. officials are worried that Obama’s reluctant decision to provide limited amounts of small arms and ammunition to the Syrian opposition is enough to drag the U.S. into a third Mideast war but not enough to win it.

[. . .]

The most perverse twist, even given the complicated politics of the 
Middle East, is that the U.S. now finds itself sharing a goal with the Sunni extremist groups allied with al-Qaeda that are seeking to replace Assad’s secular regime with Islamic rule, said one of the officials. While the Islamists’ vision of a post-Assad Syria is clear, Obama’s isn’t, this official said.

Both officials said the Obama administration has done virtually no planning for a postwar Syria, much as President 
George W. Bush’s administration had no road map for Iraq after the U.S. invasion other than a dead-on-arrival plan to put Iraqi exile Ahmed Chalabi in power.

This intervention has not been thought through. So why is it happening?