Editing Naval mine (section)

==== Mine sweeping ====
[[File:MH-53E Sea Dragon towing sled.jpg|thumb|An [[CH-53E Super Stallion|MH-53E]] from [[HM-15]] tows a [[minesweeping]] sled while conducting simulated mine clearing operations]]
[[File:USS Tide sinking.jpg|thumb|[[Minesweeper]] {{USS|Tide|AM-125|6}} after striking a mine off [[Utah Beach]], 7 June 1944. Note her broken back, with white smoke billowing amidships.]]
{{main|Minesweeping}}

A sweep is either a contact sweep, a wire dragged through the water by one or two ships to cut the mooring wire of floating mines, or a distance sweep that mimics a ship to detonate the mines. The sweeps are dragged by [[minesweeper (ship)|minesweeper]]s, either purpose-built military ships or converted [[Commercial trawler|trawlers]]. Each run covers between {{convert|100|and|200|m|ft|spell=in}}, and the ships must move slowly in a straight line, making them vulnerable to enemy fire. This was exploited by the Turkish army in the [[Battle of Gallipoli]] in 1915, when mobile [[howitzer]] batteries prevented the British and French from clearing a way through minefields.

If a contact sweep hits a mine, the wire of the sweep rubs against the mooring wire until it is cut. Sometimes "cutters", explosive devices to cut the mine's wire, are used to lessen the strain on the sweeping wire. Mines cut free are recorded and collected for research or shot with a deck gun.<ref>{{cite web |url=http://www.ussimplicitmso-455.com/Minesweeping.html |archive-url=https://web.archive.org/web/20090402163450/http://www.ussimplicitmso-455.com/Minesweeping.html |archive-date=2009-04-02 |title=Mine Sweeping Operations |work=Minesweeping |publisher=Charles Lees |access-date=2011-12-31 |url-status=dead }}</ref>

Minesweepers protect themselves with an [[Oropesa (minesweeping)|oropesa]] or [[Paravane (weapon)|paravane]] instead of a second minesweeper. These are torpedo-shaped towed bodies, similar in shape to a [[Harvey torpedo]], that are streamed from the sweeping vessel thus keeping the sweep at a determined depth and position. Some large warships were routinely equipped with paravane sweeps 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. More recently, heavy-lift helicopters have dragged minesweeping sleds, as in the 1991 Persian Gulf War.<ref>{{cite web |url=http://www.merriam-webster.com/dictionary/paravane |title=Paravane – Definition and More from the Free Merriam-Webster Dictionary |publisher=Merriam-webster.com |access-date=2011-12-31 |archive-date=28 January 2012 |archive-url=https://web.archive.org/web/20120128171755/http://www.merriam-webster.com/dictionary/paravane |url-status=live }}</ref>

The distance sweep mimics the sound and magnetism of a ship and is pulled behind the sweeper. It has floating coils and large underwater ''drums''. It is the only sweep effective against bottom mines.

During WWII, [[RAF Coastal Command]] used [[Vickers Wellington]] bombers Wellington DW.Mk I fitted with degaussing coils to trigger magnetic mines.<ref>{{cite web |url=http://www.wwiivehicles.com/unitedkingdom/aircraft/bomber/vickers-wellington.asp |title=Britain's Vickers Wellington bomber, 'Wimpey' |work=World War II Vehicles, Tanks, and Airplanes |publisher=Wwiivehicles.com |access-date=2011-12-31 |archive-url=https://web.archive.org/web/20111118105920/http://www.wwiivehicles.com/unitedkingdom/aircraft/bomber/vickers-wellington.asp |archive-date=2011-11-18 |url-status=dead }}</ref> In a parallel development the Luftwaffe adapted some Junkers 52/3m aircraft to also carry a coil operated by electricity supplied from an onboard generator. The Luftwaffe called this adaption ''Minensuch(e)'' (lit. mine-search).{{Sfn|Smith|1966|p=16}} In both cases pilots were required to fly at low altitude (up to about 200 feet above the sea) and at fairly low speeds to be effective.

Modern influence mines are designed to discriminate against false inputs and are, therefore, much harder to sweep. They often contain inherent anti-sweeping mechanisms. For example, they may be programmed to respond to the unique noise of a particular ship-type, its associated magnetic signature and the typical pressure displacement of such a vessel. As a result, a mine-sweeper must accurately mimic the required target signature to trigger detonation. The task is complicated by the fact that an influence mine may have one or more of a hundred different potential target signatures programmed into it.<ref name="ReferenceB">{{cite web |url=https://fas.org/man/dod-101/navy/docs/swos/cmd/miw/Sp6-4-1/sld034.htm |title=Mine Counter-Counter Measures (MCCM) |last=Garrold |first=Tim |work=Mine Warfare Introduction: The Threat |publisher=Surface Warfare Officers School Command, U.S. Navy |date=December 1998 |access-date=2011-12-31 |archive-date=4 March 2016 |archive-url=https://web.archive.org/web/20160304064742/http://fas.org/man/dod-101/navy/docs/swos/cmd/miw/Sp6-4-1/sld034.htm |url-status=live }} Slide 34 of 81. Hosted by Federation of American Scientists.</ref>

Another anti-sweeping mechanism is a ship-counter in the mine fuze. When enabled, this allows detonation only after the mine [[fuze]] has been triggered a pre-set number of times. To further complicate matters, influence mines may be programmed to arm themselves (or disarm automatically—known as ''self-sterilization'') after a pre-set time. During the pre-set arming delay (which could last days or even weeks) the mine would remain dormant and ignore any target stimulus, whether genuine or false.<ref name="ReferenceB"/>

When influence mines are laid in an ocean minefield, they may have various combinations of fuze settings configured. For example, some mines (with the acoustic sensor enabled) may become active within three hours of being laid, others (with the acoustic and magnetic sensors enabled) may become active after two weeks but have the ship-counter mechanism set to ignore the first two trigger events, and still others in the same minefield (with the magnetic and pressure sensors enabled) may not become armed until three weeks have passed. Groups of mines within this mine-field may have different target signatures which may or may not overlap. The fuzes on influence mines allow many different permutations, which complicates the clearance process.<ref name="ReferenceB"/>

Mines with ship-counters, arming delays and highly specific target signatures in mine fuzes can falsely convince a belligerent that a particular area is clear of mines or has been swept effectively because a succession of vessels have already passed through safely.