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The first naval mines may have been tried by the English at the Seige of Rochelle in 1627 where they launched "floating petards" unsuccessfully against the French navy.
However, the first practical ones were invented by an American, David Bushnell, for use against the British in the American War of Independence. It was a watertight keg filled with gunpowder and fired by a percussion lock when the keg stuck a ship.
The first successful use occured during the American Civil War, where mines were widely used by both sides. The first ship sunk was USS Cairo in 1863 in the Yazoo River. Rear-Admiral David Farragut's famous quote, "Damn the torpedoes!" refers to a minefield laid at Mobile, Alabama.
In the nineteenth century, mines were universally called torpedoes, a term probably first adopted by Robert Fulton, and named after a fish which can give powerful electric shocks. Only later was it reserved for self-propelled underwater missiles, originally called Whitehead Torpedoes after the inventor. As well as self-propelled torpedoes and fixed mines, there were types of "torpedoes" which were attached to an attacking ship.
A spar torpedo was a mine attached to a long pole and detonated by the ship carrying it ramming another one. Perhaps the best known use was the destruction of USS Housatonic by CSS Hunley on February 17 1864.
A Harvey Torpedo was a type of floating mine which was towed alongside a ship, and was briefly in service in the Royal Navy in the 1870s.
The next major use came in the Russo-Japanese War in 1904, where the Russian battleship Petropavlovsk was sunk, killing most of the crew including the fleet commander, Admiral Makaroff.
The earliest mines were usually of this type. They detonate when a ship comes into physical contact with them. They float just below the surface of the water and are prevented from drifting by cables connecting them to weights on the seabed. The explosive and detonating mechanism is contained in a metal shell which also has a considerable airspace within it to provide buoyancy. The depth below the surface at which the mine floats can sometimes be set so that only large draft vessels such as aircraft carriers or battleships were at risk.
Early mines had mechanical mechanisms to detonate them, but these were superseded in the 1870s by the Hertz Horn which was found to work reliably even after the mine had been in the sea for several years. In this, the top of the mine has hollow studs a few inches long made out of lead. Each of these contains a glass vial filled with sulphuric acid. When a ship strikes the mine, the metal horn is crushed, destroying the vial inside it. The acid then runs down a tube and into a lead-acid battery which until then contains no acid electrolyte. At this point the battey is energised, which detonates the explosive.
During the First World War, the British heavily mined the English Channel and later large areas of the North Sea to prevent German submarines from using it. As the submarine could be at any depth down to the seabed, a US invention, the antenna mine, was widely used. This had a copper wire which the floated on a buoy above the mine, and the top part of the cable connecting it to the weight on the seabed was also made of this metal. It was insulated from the steel cable below it. If a submarine's steel hull touched the copper wire then the slight voltage produced because of the two disimilar metals was amplified and detonated the explosive.
Contact mines can be destroyed by minesweepers. These were small shallow draft ships which operated in pairs a hundred metres or so apart and dragging a serrated wire between them. The wire would slide up to the top of the mooring cable where it touched the mine and cut it free. Once the cable was cut the mine would float to the surface where a rifleman would shoot at it. This would either detonate it, or more often puncture it so that it sank. Some mines (especially antenna mines) might detonate harmlessly underwater just from contact with the dragline. Commandeered trawlers were often used as minesweepers as they were nearly ideal for the task, and usually came with the necessary winches.
The only problem with this technique, apart from the obvious risk from the mines, was the inability of minesweepers to manoeuvre without tangling the cable if they were attacked by aircraft - a major problem in the Second World War. To minimize this risk, one of the minesweepers would be substituted with a paravane, a torpedo-shaped float similar in shape to a Harvey Torpedo and so pulled away sideways from the ship towing it. Some large warships were routinely equipped with paravanes near the bows in case they inadvertently sailed into minefields - the mine would be deflected towards the paravane by the wire instead of towards the ship by its wake.
There were two countermeasures to dragline sweeping. The first was an ingenious mechanism which could be fitted near to the top of the mooring cable. It would allow the cutting wire to pass through it without disconnecting the mine. The other, more effective countermeasure was to have the mined area covered by gunfire or aircraft. This was most effectively done by the Turkish army in the Dardanelles in 1915, where mobile howitzer batteries prevented the British and French from clearing a way through.
Drifting mines were occasionally used, although usually the fear of them was more effective than they were themselves. Admiral Jellicoe's British fleet did not pursue and destroy the outnumbered German High Seas Fleet when it turned away at the Battle of Jutland because he thought they were leading him into a trap. He believed that either the germans were leaving floating mines in their wake, or were drawing him towards submarines. Both dangers were imaginary - the German fleet did not carry any mines.
Churchill promoted "Operation Marine" in 1940 and again in 1944 where floating mines were put into the Rhine in France to float down the river, becoming active after a fixed interval by which time they should have reached German territory.
These are mines which do not need physical contact with the ship to detonate it. The earliest ones were moored mines used in the American Civil war and detonated electrically by observers on the shore. These were seen as superior to contact mines because they only deprived the waterway to the enemy.
More modern ones are self-acting and lie on the seabed, but can only be used in shallow water, otherwise the mine will explode too far away to damage the ship. An exception is the American CAPTOR mine which fires a torpedo. The first self-acting non-contact mines appeared at the end of the First World War and were detonated by the vertical component of the natural magnetic field of a ship passing overhead. They were further developed by the Germans in the Second World War, who introduced other techniques such as using the sound of a ship or the change in seawater pressure to detonate them.
Magnetic mines were largely countered by ships towing floating cables through which high currents were pulsed, creating strong magnetic fields to detonate them. Ships could also be immunised against the mines initially by installing magnetic coils around the hulls to neutralise the magnetic field and later by degaussing, the process of neutralising the field by remagnetising the hull. So effective where these countermeasures that redundant german mines were used as bombs.
Acoustic mines were cleared by towing a noise-making device behind the ship, and pressure sensitive ones were destroyed by tides. However large ships had to travel slowly in waters suspected of containing pressure mines.
Modern non-contact mines are much more sensitive and much harder to sweep. They often contain anti-sweeping mechanisms such as sensitivity only to the noise of certain types of ship or will detonate only after their mechanism has been triggered a set number of times. They may also only arm themselves (or disarm automatically) after a set time. A different type of ship is needed to counter them, known as a mine hunter. A mine hunter may for example carry remotely piloted submersibles which can physically examine suspected mines initially located using sonar.
During the Gulf War, Iraqi naval mines severely damaged USS Princeton (CG-59) and USS Tripoli (LPH-10).
The United States Navy MK56 ASW mine (the oldest still in use by the US) was developed in 1966. Since that time, more advances in technology have given way to the development of the MK60 CAPTOR (short for "encapsulated torpedo"), the MK62 and MK63 Quickstrike and the MK67 SLMM (Submarine Launched Mobile Mine). Most mines in the USN's arsenal today are delivered by aircraft to target.
Early History
Classes
Static mines may be classified into two types.Contact mines
Non-Contact mines
MK67 SLMM Submarine Launched Mobile Mine
The SLMM was developed by the United States as a submarine deployed mine for use in areas inaccessible for other mine deployment techniques or for covert mining of hostile environments. The SLMM is a shallow water mine consisting basically of a modified MK37 torpedo.
General Characteristics
MK65 Quickstrike
The Quickstike is a family of shallow water aircraft laid mines used by the United States primarily against surface craft. The MK65 is a 2,000 lb mine. Other Quickstrike versions (MK62, MK63, and MK64) are converted general purpose bombs of the 500 pound and 1000 pound sizes.
General Characteristics
MK60 CAPTOR
The CAPTOR is the United States Navy's primary anti-submarine weapon. This deep water mine is designed to be laid by aircraft or submarine, and is anchored to the ocean floor. Upon detection of a hostile submarine, the CAPTOR launches a MK46 Mod 4 torpedo.
General Characteristics
MK56
General Characteristics