The MK 15 Phalanx Close-In Weapons
System (CIWS - pronounced "sea-whiz") is a fast-reaction, rapid-fire
20-millimeter gun system that provides US Navy ships with a terminal
defense against anti-ship missiles that have penetrated other fleet
defenses. Designed to engage anti-ship cruise missiles and fixed-wing
aircraft at short range, Phalanx automatically engages functions usually
performed by separate, independent systems such as search, detection,
threat evaluation, acquisition, track, firing, target destruction, kill
assessment and cease fire.