That means the long-dormant concrete pads at the ends of this base’s 11,000-foot runway — dubbed the “Christmas tree” for their angular markings — could once again find several B-52s parked on them, laden with nuclear weapons and set to take off at a moment’s notice. “This is yet one more step in ensuring that we’re prepared,” Gen. David Goldfein, Air Force chief of staff, said in an interview during his six-day tour of Barksdale and other U.S. Air Force bases that support the nuclear mission. “I look at it more as not planning for any specific event, but more...