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President Obama explained his decision to dismiss General Stanley McChrystal yesterday by noting that he had a duty "to ensure that no diversion complicates the vital mission" that American forces are carrying out in Afghanistan. Fair enough. We don't begrudge the President's right to make that call, and no one is better qualified than General David Petraeus to replace his former deputy and run a counterinsurgency.

The larger questions now are whether the President can exert as much policy discipline over his civilian subordinates as he has on the military—and whether he's willing to make a political investment in the war commensurate with the military sacrifice.