procedures. All personnel should be off the ship before  the  commanding  officer  leaves  the  ship. For  centuries,  the  commanding  officer  has  had complete  authoritative  power.  With  ultimate responsibility  for  the  ship  and  everything pertaining  to  it,  the  CO  obviously  requires  the authority  to  go  with  it.  The  CO  must  have  the power  to  enforce  prompt  obedience  to  orders  to maintain  efficiency  and  discipline.  As  set  forth in the Uniform Code of Military Justice ( UCMJ), the commanding officer has the power to impose limited   punishment.    This   power   to   impose punishment  is  a  part  of  command  and  may  not be delegated. The  commanding  officer  shoulders  constant concern   for   the   welfare,   morale,   and   living conditions  of  the  crew.  The  CO  receives  help  in these  areas  from  an  enlisted  adviser  known  as  the command  master  chief  (CM/C),  command  senior chief (CS/C), or command chief (CCh). A master chief detailed by the Bureau of Naval Personnel to  the  command  or  a  master  chief,  senior  chief, or  chief  petty  officer  appointed  by  the  CO,  as appropriate,  serves  as  the  senior  enlisted  adviser. This person has direct access to the commanding officer.  In  addition,  the  enlisted  adviser  maintains contact with the master chief petty officer of the Navy  (MCPON),  normally  through  the  force  or fleet  master  chief  (FM/C),  to  ensure  that  ideas and  recommendations  are  properly  transmitted. If the commanding officer is absent, disabled, relieved  from  duty,  or  detached  without  relief,  the next  senior  line  officer  eligible  for  command  at sea  attached  to  and  aboard  the  ship  assumes command. In most cases, that person will be the executive   officer   (XO). EXECUTIVE  OFFICER  (XO) As the next ranking line officer aboard ship, the   executive   officer   serves   as   the   aide   or “executive”  to  the  commanding  officer.  As  such, the   XO   is   the   direct   representative   of   the commanding  officer  in  maintaining  the  general efficiency of the ship. With the assistance of the heads   of   departments,   the   XO   arranges   and coordinates  all  ship’s  work,  drills,  exercises, personnel   organization,   and   the   policing   and inspection  of  the  ship. The  XO  investigates  matters  affecting  the discipline  and  conduct  of  the  crew  and  makes recommendations  concerning  these  matters  to  the commanding  officer.  The  XO  usually  approves or disapproves liberty lists and leave requests. If the  XO  is  unable  to  carry  out  the  duties  of  the office, the next senior line officer assigned to the ship normally assumes the duties. When  the  crew  reports  that  the  ship  is  cleared for   action,   the   XO   inspects   it   and   receives readiness  reports  from  the  various  department heads. After confirming the ship’s readiness, the XO then reports to the commanding officer that the  ship  is  ready  for  action. If   the   captain   is   disabled,   the   immediate superior  in  command  of  the  ship  (squadron  or group   commander)   designates   the   XO   as   the acting CO until a permanent commanding officer can be assigned. For this reason, the XO’s battle station, determined by the captain, is located some distance from the captain’s—a safety measure to prevent disablement of both officers at the same time.   After   each   battle,   the   executive   officer makes  a  detailed  report  to  the  commanding officer. Depending on the size of the ship, the XO may have  one  or  more  assistants.  Other  officers  are often assigned to this billet as a collateral duty. Chapter  3  of  Standard   Organization   and Regulations   of   the   U.S.   Navy   (SORN)   lists additional  duties  of  the  XO. SHIPBOARD  DEPARTMENTS The  shipboard  departmental  organization shown  in  table  16-1  includes  the  most  common types  of  naval  ships  currently  in  service.  Each particular ship type uses this table to determine the  departments  that  must  be  included  in  its administrative  organization.  Variations  should occur  only  in  exceptional  circumstances.  Most ships  have  five  basic  shipboard  departments: navigation,  operations,  weapons  (or  deck), engineering,   and   supply.   The   Chief   of   Naval Operations authorizes the establishment of other departments as necessary. The  ship  type  determines  the  number  of departments  included  in  a  shipboard  organization. Departments   are   grouped   together   as   either command   or   support   departments.   Except   in isolated  instances,  a  line  officer  eligible  to  exercise command  in  the  event  of  the  loss  of  superior officers  heads  a  command  department.  In  aircraft carriers, naval aviators head the operations and air departments. 16-2