Defense Secretary Chuck Hagel is ordering top-to-bottom changes in how the nation's nuclear arsenal is managed. And he's vowing to invest billions more to fix what ails a force beset by leadership lapses, security flaws and sagging morale.

Hagel is scheduled to announce Friday the results of two reviews — one by Pentagon officials and a second by outside experts — and to spell out actions he has ordered. Two senior defense officials discussed the Hagel plan on condition of anonymity because they were not authorized to be cited by name.

The officials say Hagel authorized the Air Force to put a four-star general in charge of its nuclear forces. Hagel concluded a four-star general would be able to exert more influence within the Air Force.