Minesweeping is the practice of the removal of explosive naval mines, usually by a specially designed ship called a minesweeper using various measures to either capture or detonate the mines, but sometimes also with an aircraft made for that purpose. Minesweeping has been practiced since the advent of naval mining in 1855 in the Crimean War. The first minesweepers date to that war and consisted of British rowboats trailing grapnels to snag the mines. By ship 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 minesweepers, either purpose-built military ships or converted trawlers. Each run covers between , 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 path 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. Before the First World War, the Imperial Russian Navy officer Pyotr Kitkin invented "mine protectors" to break a sweeping wire before it could cut the mine's mooring wire. Minesweepers protect themselves with an oropesa or 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. 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 the Second World War, RAF Coastal Command used Vickers Wellington bombers