Via Politico:

The Obama administration’s decision Thursday to provide military and political aid to anti-Assad fighters wasn’t merely a result of confirmation the Syrian regime used sarin gas on rebels — but a decision prompted by the realization that Syrian President Bashar Assad was on the cusp of gaining a permanent advantage over rebel groups and the fear of imminent sectarian bloodshed further spilling into neighboring Iraq, Jordan and Lebanon.

“The decision was ultimately driven by the discovery Assad used [chemical weapons] but there were a number of other factors in place that were also important,” conceded an administration official with direct knowledge of the deliberations.

“Would we have made [the determination Assad had breached the red line] even if we didn’t have the evidence? Probably.”

Also key in this report:

For weeks, Obama — chastened by the Iraq and Afghanistan wars — deferred passing judgment on the regime’s use of the deadly nerve gas, even as U.N. and European officials publicly reported the use of chemical weapons against hundreds of rebels and civilians.

Why the hesitation?

The president himself, people close to the situation said, has been agonizing over the decision, torn between his desire to do the right thing — and his bone-deep aversion to the kind of quick-trigger military intervention in Iraq that sidetracked his predecessor George W. Bush and resulted in the thousands of U.S. casualties.