Mines may also be described by their actuation, or detonation, methods. This description includes three types of mines: (1) contact mines, (2) controlled mines, and (3) influence mines. The U.S. Navy has no contact or controlled mines in service use. Therefore, the following paragraphs on contact and controlled mines are presented only for information.

CONTACT MINES

Contact mines are actuated by the contact of the mine cases, or their attachments, with a target. They guard a narrower path than the influence mines and are generally more vulnerable to enemy countermeasures. Their principal advantage is logistic, as they can be produced more cheaply than influence mines. Although the U.S. Navy does not use contact mines, they are still used by some nations in situations where the disadvantages are acceptable, as in protective or unprotective minefield.

CONTROLLED MINES

Controlled mines can be rendered safe, or they can be armed or fired at will from a central control station. Control mines, intended for protective use, have a limited operational utility. The U.S. Navy does not use controlled mines, but some nations, particularly those in close proximity to restricted international waterways, retain controlled mines because of the mine's unique advantage of permitting positive target selection.

INFLUENCE MINES

Influence mines are actuated by the effects of targets on the physical environments of the mines. The major operational advantage of the influence mine is that the target need not contact the mine case, thus providing greater actuation range. The U.S. Navy has only influence mines in its arsenal.

MINE PLANTING METHODS

When mines are classified according to the method by which they are delivered, they again fall into three categories: (1) aircraft-laid mines, (2) submarine-laid mines, and (3) surface-laid mines.

AIRCRAFT-LAID MINES

Aircraft carry mines the same way they carry bombs or torpedoes, internally (inside the bomb bay) or externally (on wing stations). The following are some of the advantages of aircraft-laid mines:

*Aircraft can carry mines into enemy-held areas where minefield can be reseeded over a long period of time without danger to the aircraft from previously planted mines.

Aircraft can plant mines in enemy-held shallow coastal waters where other planting methods cannot be used.

*Aircraft mine laying is an effective planting method for blockading enemy shipping lanes. However, a disadvantage is that this type of planting cannot be done in secrecy.