>> such innocent children there. all right, a few hours from now the u.s. president will announce his choice for secretary of defense, outgoing secretary chuck hagel incisions his departure is the result of a mutual agreement with president barack obama. thursday he spoke about america's challenges ahead and his decision to leave now. >> all of us together, not secretary hagel but all of us as a team have prepared this institution over the last two years to take on these big issues that are ahead. those issues are still undefinable. we know of some of them. we know of long-term challenges, but i think you have to know when to leave too. >> the nominee to succeed hagel is expected to be this man, ashton carter who had been the pentagon's second in command. now, outside of isis another