Service leaders took an assessment last year of the nuclear Air Force as an encouraging thumbs-up. Yet, in the months that followed, signs emerged that the nuclear missile corps was suffering from breakdowns in discipline, morale, training and leadership.

The former Air Force chief of staff who signed off on the 2013 report is now being asked to dig for root causes of problems that Defense Secretary Chuck Hagel says threaten to undermine public trust in the nation’s nuclear arsenal.