The anniversary of the Sept. 11 attacks is in a sort of transition phase. The wounds are no longer fresh after 18 years, but the terrible day is not yet enshrined in the deep historical past. That makes it a good time to take stock of what’s been achieved in the fight against global terrorism, and what remains to be done. I can think of no better person to discuss this than Philip Zelikow. Now a professor of governance at the University of Virginia’s Miller Center, Zelikow had a long career inside government, rising to counselor of the State Department under President George W. Bush. But he’s best known for his role as executive director of the federal 9/11 Commission, and thus is the primary author of the commission’s report on the attacks.