'Antisubmarine warfare involves at least four activities that proceed in a logical sequence; intelligence, detection, localization and destruction.

Intelligence includes such information as the number of enemy submarines of each class, for example submarine (SS), nuclear-powered attack submarine (SSN), ballistic-missile-launching submarine (SSB), nuclear-powered ballistic-missile-launching submarine (SSBN) or cruise-missile-launching submarine (SSG or SSGN). Other kinds of information such as the number and range of missiles, number and type of torpedoes, speed and endurance, noise level, and sonar and radar capability is also important.

Detecting a submarine in the immense background of ocean noise requires discrimination or processing gain. The desired source is known to be a point within a few hundred metres of the surface. Moreover, the source can be assumed to have a stationary spectrum in which there are usually strong line components. For decades large cadres of competent technicians have been working on the problems of extracting the submarine's "signal" from the noise in which it is immersed; the result has been a large variety of systems emphasizing different choices of available parameters, guided by operational considerations, analysis or tradition.

After a submarine has been detected in a certain target area, say an area 50 kilometres square, the next step is to pinpoint its position. Localization can be done from the air, from the surface or from below the surface.

The US Navy has two principal weapons for destroying enemy submarines: the lightweight 12-inch Mark 46 active acoustic homing torpedo and the full-size 21-inch Mark 48 active-passive acoustic homing torpedo (which was just coming into service in 1972). The 12-inch torpedo was essentially the only effective antisubmarine weapon available to aircraft and helicopters. The Mark 48 is a long-range torpedo with a large warhead; when launched by a hunter-killer submarine, it can be guided electrically by means of a control wire. Like any other weapon, a homing torpedo will not be perfectly reliable in actual combat, and it may be vulnerable to countermeasures."