and sustained combat operations at sea. Opera- tions  include  sea-based  aircraft  and  land-based naval air components. In effect, these forces seek out and destroy enemy naval forces and suppress enemy  sea  commerce.  They  gain  and  maintain general naval supremacy, control vital sea areas, and  protect  vital  sea  lines  of  communications. They  also  establish  and  maintain  local  superiority in land and air operations and seize and defend advanced  naval  bases. The  Navy  also  provides  forces  for  joint amphibious operations. It is responsible for train- ing  all  forces  assigned  to  these  operations  in amphibious  warfare  as  directed  by  Joint  Chiefs of  Staff.  Other  specific  responsibilities  assigned to  the  Navy  are  naval  reconnaissance,  antisub- marine  warfare,  protection  of  shipping,  mine- laying,  and  controlled  minefield  operations.  In conjunction  with  the  other  services,  the  Navy provides  forces  for  the  defense  of  the  United States against air attack. Because  of  the  complexity  of  the  Navy’s function, a massive modernization of Navy ships, aircraft,  and  weapons  has  been  undertaken. Basically,   the   modernization   has   taken   three forms:  (1)  the  speedup  of  research  and  develop- ment  to  develop  new  weapons;  (2)  laying  up  of old  ships  to  save  operating  and  overhauling  costs, thereby directing this money into new construc- tion;  and  (3)  the  “hi-low  balanced  mix”  concept. This hi-low concept is a balance in the purchase of a few highly effective ships and aircraft, such as  CVNs,  SSBNs,  and  F/A-18  aircraft,  with  a concurrent  development  of  new  classes  of  low-cost ships,  such  as  guided-missile  frigates. The Navy has entered a new phase of scientific warfare—one  in  which  nuclear  weapons  and guided  missiles  are  the  primary  destructive weapons.  Conventional  weapons,  of  course,  are still   maintained   and   being   improved.   Such weapons   enable   the   Navy,   with   its   Marine component,  to  deploy  rapidly  and  to  apply  the force  necessary  to  contain  a  limited  war. The Navy’s achievements in the development of  scientific  projects  continue  to  lead  the  world. These achievements range from earth navigation and  communications  satellites  to  the  improvement of nuclear propulsion. The Navy’s Polaris missile, operational  in  nuclear-powered  submarines  at  sea, was the first intermediate-range ballistic missile (IRBM) to be equipped with the solid-propellant motor. The Poseidon and Trident missiles, which have  extended  range  and  multiple  warheads,  were developed  following  the  success  of  the  Polaris missile.  They  have  since  replaced  the  Polaris. Other Navy achievements include pioneering new  developments  in  communications,  naviga- tion, underwater acoustics, oceanography, and a host   of   other   scientific   fields.   One   particular achievement  is  the  successful  pioneering  of  the route from the Pacific to the Atlantic beneath the North  Polar  ice  cap. The  Navy  has  divided  its  mission  into  four functional areas: (1) strategic deterrence, (2) sea control,  (3)  projection  of  power  ashore,  and  (4) naval  presence. Strategic  Deterrence Strategic deterrence has three objectives. The first  of  these  is  to  deter  (prevent  or  discourage) an all-out attack on the United States or its allies. The  second  objective  is  to  cause  any  possible attacker to face an unacceptable risk in the event of  an  attack.  The  final  objective  is  to  keep  the United States and its allies politically stable and secure enough to withstand the threat of attack or   blackmail. How does the Navy accomplish the objectives of strategic deterrence? First, the Navy maintains an   ASSURED   SECOND-STRIKE   CAPABIL- ITY. This means that if an enemy were to launch an all-out attack, the United States could deliver massive retaliation (counterattack) even after the attack.  The  Navy’s  fleet  ballistic  missile  sub- marines  (nuclear)  (SSBNs)  are  the  backbone  of this  tactic  because  of  their  high  probability  of surviving  a  nuclear  attack.  Second,  the  tactic  of CONTROLLED RESPONSE is used. This means that the Navy will respond to a partial attack only to the degree required. This is hoped to prevent a general nuclear war. The SSBN fleet is also the backbone  of  this  tactic. Sea  Control Our   nation’s   definition   of   sea   control   is denying  the  use  of  the  sea  to  our  enemy  and assuring the use of the sea to the United States and  its  allies.  In  today’s  world,  sea  control  can be  exercised  only  over  limited  areas  of  the  sea. Although sea control is accomplished by four tactics, many weapons and weapons systems can be used with these tactics. The correct tactic and weapons  systems  to  be  used  depends  on  the  situa- tion.  The  four  tactics  used  to  accomplish  sea control  are  as  follows: 1.  SORTIE  CONTROL  is  used  to  keep  an enemy  within  ports  and  bases.  As  the  enemy 1-13