Clearing a naval minefield can take 200 times longer than laying it
A naval mine can cost as little as 2,000 dollars, and laying one typically costs between 0.5 and 10 percent of removing it. Clearing a minefield may take up to 200 times as long as sowing it, which is why parts of some World War II minefields have never been cleared.
Mines sit in the water until a passing ship triggers them by contact or proximity. Used offensively they bottle up harbours and choke shipping lanes; used defensively they shield coasts and force enemies toward well-guarded waters. An opponent must then sweep at great cost, accept losses, or sail where defenders concentrate their firepower. Because shipowners avoid known minefields, a single well-placed mine can halt traffic for days while an area is swept, and thinly spread fields can suggest danger across huge areas. Minefields work more on minds than on hulls.
The Eighth Hague Convention of 1907 requires nations to announce mining, but not precisely; in World War II Britain simply declared that it had mined the English Channel, the North Sea and the French coast.
Chinese inventors came first. The 14th-century Huolongjing of the Ming officer Jiao Yu describes naval mines, and in the 16th century General Qi Jiguang set timed drifting charges against Japanese pirates. A treatise of 1637 by Song Yingxing shows a mine fired by a ripcord pulled by ambushers on shore, spinning a steel wheel against flint. In the West, Ralph Rabbards pitched a sea mine to Elizabeth I in 1574. During the American Revolution David Bushnell floated gunpowder kegs at HMS Cerberus in 1777, sinking only her tender.
Robert Fulton's devices for the 1804 raid on Boulogne included a low-riding torpedo-catamaran steered by a paddler in dark clothes. In 1812 the Russian engineer Pavel Shilling set off an underwater mine electrically, and in 1842 Samuel Colt demonstrated an electrically fired mine to President John Tyler, only for John Quincy Adams to condemn it as unfair warfare. In the Crimean War Russia laid more than 1,500 mines designed by Moritz von Jacobi and Immanuel Nobel in the Gulf of Finland, prompting the first minesweeping operation, which cleared 33 mines in 72 hours.
Source: Naval mine
