In the maritime theater of war, one of the greatest threats to vessels tends to be anti-ship missiles and other air-borne payloads. Considering the extremely limited mobility and massive size of naval vessels, one of the only options to counter these threats is to destroy them in air so that the payload is neutralized at a safe distance away from the ship.
The Phalanx CIWS (close in weapons system) was on the pioneers in this domain and continues to push the envelope in terms of accuracy, radar technology and over efficacy. However, as missile propulsion technology continues to evolve and they can perform ever more dexterous motions in midair, the limitations of the gun system (where the system predicts a point in space and attempts to intercept the missile midair) become more and more dramatic. The types of weapons that make this disparity most dramatic are called highly maneuverable standoff weapons (SOWs) which have the ability to quickly alter their direction during an engagement.