Last fall, as President Obama weighed airstrikes against Syria, deliberations followed a clear pattern: The president solicited scores of options, planners returned with possibilities, and, according to people involved, Obama would reply with the same question: And then what?

Over the last several days, with Obama mulling involvement in another Middle East conflict, this time in Iraq, that dynamic has held.

....Obama's approach — the persistent "and then what?" question — reflects his deep skepticism about the ability of military intervention to fix entrenched problems, a suspicion that some note has grown, or at least solidified, during his tenure.

....That view won support Wednesday from the general who was the architect of the so-called troop surge under George W. Bush. The U.S. should reengage militarily in Iraq only if the country's sectarian communities reach a political agreement, retired Gen. David Petraeus said at a conference in London. "This cannot be the United States being the air force for Shia militias, or a Shia on Sunni Arab fight," he said.