Ten years ago next month, the U.S. military changed tack in a messy Iraq occupation, launching what’s simply known as “the surge.” Today, experts are still fighting over it. Even among those who credit Gen. David Petraeus and his counterinsurgency (COIN) strategy with turning the Iraq War around, there are competing theories on why it worked. Some have argued forcefully that it wasn’t the surplus of American troops or shift in tactics that put an end to the sectarian war that rocked Iraq in the months leading up to the surge, but rather that the war had simply bled itself out by the time we decided to get involved. Those who say it didn’t work at all can point to the subsequent rise of ISIS — whose leader, Abu Bakr al-Baghdadi, was reportedly radicalized while being held in a U.S. detention facility — and the fact that Baghdad is now firmly under Iranian control; here, they argue, is proof that the surge did little more than allow the U.S. to leave Iraq with its dignity intact.