Minesweeper ( ship ) A minesweeper is a small naval warship designed to counter the threat posed by naval mine s . Minesweepers keep waterways clear for shipping . History . Although naval warfare has a long history , naval mine s were not deployed until 1855 in the Crimean War . The first minesweepers date to that war and consisted of British rowboats trailing grapnel s to snag the mines . Despite the use of mines in the American Civil War , there are no records of effective minesweeping being used . Officials in the Union Army attempted to create the first minesweeper but were plagued by flawed designs and abandoned the project . Minesweeping technology picked up in the Russo - Japanese War , where aging torpedo boats were pressed into sweeping service in 1908 and more boats were purchased for the purpose the following year . In Britain , naval leaders recognized before the outbreak of World War I that the development of sea mines was a threat to the nation ' s shipping and began efforts to counter the threat . Sir Arthur Wilson noted the real threat of the time was blockade aided by mines and not invasion . The function of the fishing fleet ' s trawlers with their trawl gear was recognized as having a natural connection with mine clearance and , among other things , trawlers were used to keep the English Channel clear of mines . A Trawler Section of the Royal Navy Reserve became the predecessor of the mine sweeping forces with specially designed ships and equipment to follow . These reserve Trawler Section fishermen and their trawlers were activated , supplied with mine gear , rifles , uniforms and pay as the first minesweepers . The dedicated , purpose - built minesweeper first appeared during World War I with the Flower - class minesweeping sloop . By the end of the War , naval mine technology had grown beyond the ability of minesweepers to detect and remove . Minesweeping made significant advancements during World War II . Combatant nations quickly adapted ships to the task of minesweeping , including Australia ' s 35 civilian ships that became Auxiliary Minesweepers . Both Allied and Axis countries made heavy use of minesweepers throughout the war . Historian Gordon Williamson wrote that " Germany ' s minesweepers alone formed a massive proportion of its total strength , and are very much the unsung heroes of the Kriegsmarine . " Naval mines remained a threat even after the war ended , and minesweeping crews were still active after VJ Day . After the Second World War , allied countries worked on new classes of minesweepers ranging from 120 ton designs for clearing estuaries to 735 ton ocean going vessels . The United States Navy even used specialized Mechanized Landing Craft to sweep shallow harbors in and around North Korea . , the U . S . Navy had four minesweepers deployed to the Persian Gulf to address regional instabilities . Operation and requirements . Minesweepers are equipped with mechanical or influence sweeps to detonate mines . The modern minesweeper is designed to reduce the chances of it detonating mines itself ; it is soundproofed to reduce its acoustic signature and often constructed using wood , fiberglass or non - ferrous metal , or is degaussed to reduce its magnetic signature . Mechanical sweeps are devices designed to cut the anchoring cables of moored mines , and preferably attach a tag to help the subsequent localization and neutralization . They are towed behind the minesweeper , and use a towed body ( e . g . oropesa , paravane ) to maintain the sweep at the desired depth and position . Influence sweeps are equipment , often towed , that emulate a particular ship signature , thereby causing a mine to detonate . The most common such sweeps are magnetic and acoustic generators . There are two modes of operating an influence sweep : MSM ( mine setting mode ) and TSM ( target simulation mode or target setting mode ) . MSM sweeping is founded on intelligence on a given type of mine , and produces the output required for detonation of this mine . If such intelligence is unavailable , the TSM sweeping instead reproduces the influence of the friendly ship that is about to transit through the area . TSM sweeping thus clears mines directed at this ship without knowledge of the mines . However , mines directed at other ships might remain . The minesweeper differs from a minehunter ; the minehunter actively detects and neutralises individual mines . Minesweepers are in many cases complementary to minehunters , depending on the operation and the environment ; a minesweeper is , in particular , better suited to clearing open - water areas with large numbers of mines . Both kinds of ships are collectively called mine countermeasure vessel s ( MCMV ) , a term also applied to a vessel that combines both roles . The first such ship was HMS " Wilton " , also the first warship to be constructed from fiberglass . Minesweeping aircraft . Aircraft can also be used for minesweeping . During World War II , fifteen British Vickers Wellington bomber s were modified to carry a large magnetic induction loop and an electrical generator . The ' Directional Wireless Installation ' ( DWI ) , a cover story for the true purpose of the magnetic loop , was used successfully on May 10 , 1940 to sweep a path for the escape of the Dutch Royal Family to the UK . The DWI was used most successfully in the Mediterranean theatre , particularly over the Suez Canal and Alexandria Harbour . Their use revealed the limitations of the technique , in that it only works effectively in very shallow water ( such as canals and harbours ) . From about 1943 , German Junkers Ju 52 transports were similarly converted . Blohm & Voss BV 138 MS tri - engine flying boats were also used for this purpose . The MH - 53E Sea Dragon helicopter , which tows a minesweeping sled , is used by the United States Navy for minesweeping