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Mr. Merrill is a frequent co11tribt11or to THE SUBMARINE REVIEW and is a published author of several books a11 the histo1y of undersea technology. He is a retired engineer with lengthy experience at the New London Lab of the Naval Undersea Warfare Center. He currently lives in Waterford, CT.

Sea Mines, The Submarines’ Adversarv and Weapon: 1775 to 1918. Part I appeared in the January 2005 issue.

At the beginning of the new century, the relatively short Russo-Japanese War of 1904-05 brought naval encounters in the northern Pacific that proved costly in lives lost at sea and on land. Some of the losses were due to the defensive and offensive use of sea mines. It was a testing ground for sea mines against modem naval ships. Russian defensive mines prevented the Japanese from attacking Port Arthur, and the Japanese offensive use of mines impeded Russian ship movement to open seas.

Both sides as well as non-belligerents suffered severe losses from mines. In addition, there were self-losses by mining vessels. A further hazard from mines occurs when, due to storms or failure of mooring, the mines become adrift. Drifting mines as a danger continued throughout the century with hundreds of thousands planted in the various oceans.

This 19-month war focused attention to mines as an effective weapon, as can be seen by their broad use in successive wars at sea during the remainder of the 20’h century. Previously, mines were placed in shallow water as an inshore weapon. In this war both sides used the mines in deep water. Russian mines were the cause of the largest number of Japanese ship losses. 22 The successful use of mines by the belligerents signaled mines had become an integral part of naval warfare.

Losses from Mines

The August 1905 peace negotiations held in Portsmouth, New Hampshire, and mediated by President Theodore Roosevelt resolved the conflict. There were additional impacts from the mines used during the war. Non-belligerent merchant ships were destroyed by mines adrift in the Yellow Sea because of poorly designed moorings or displacement by storms. It is interesting to note that no torpedo sinkings occurred during the war.

The Hague International Convention
With 44 nations participating, the Second Hague Peace Conference held from June until October of 1907 addressed the topic of sea mines. Increasing use of mines in wars from the middle of the 191-century and extensive use of mines during the Russo-Japanese War prompted the need for international regulation. Recognition of the efficacy and fear of sea mines is seen in Laws of War: Laying of Automatic Submarine Contact Mines (Hague VIII); October 18, 1907. Not all the participating nations had significant maritime interests. During the meetings, Great Britain was unsuccessful in convincing Germany and Russia to dispense with the use of mines altogether. This lack of agreement, especially between Great Britain and Germany, weakened the outcome of the Convention.

The Convention ended with thirteen agreed-upon provisions. Articles one and five were clear and unequivocal. Austria-Hungary, Japan and the United States ratified the convention unconditionally; France and Germany ratified it except Article 2; Great Britain ratified with a declaration; and Greece, Italy, Portugal, Russia, Spain and the South American Republics did not ratify it at all.

Article 1. It is forbidden-I To lay unanchored automatic contact mines, except when they are to become harmless one hour at most after the person who laid them ceases to control them; 2 To lay anchored automatic contact mines which do not become harmless as soon as they have broken loose from their moorings; 3 To use torpedoes which do not become harmless when they have missed their mark.

Article 2. Which forbids the laying of contact mines off the coast and the ports of the enemy, with the sole object of intercepting commercial shipping, is of limited value, for a belligerent has only to allege that mines were laid for a purpose other than merely intercepting commercial navigation.

Article 5. At the close of the war, the contracting Powers under-take to do their utmost to remove the mines which they have laid, each Power removing its own mines.
As regards anchored automatic contact mines laid by one of the belligerents off the coast of the other, their position must be notified to the other party by the Power which laid them, and each Power must proceed with the least possible delay to remove the mines in its own waters.

It is of interest that in 1907, the significance of sea mines on both navy and commercial navigation was fully sensed. The Articles relating to mines were scheduled to be effective in January of 1910. A second Convention addressing mines was scheduled for 1914, the year that World War I started, with mines becoming a significant weapon. Difficult to enforce, the mine-related Articles had little impact on the development of mines and mine warfare.

After World War I, the drifting contact mine was banned, even if it was occasionally used during World War II. The drifting mines were much harder to remove after the war, and they caused about as much trouble to both sides.

The agreements agreed upon at The Hague were largely unenforceable. From a military standpoint they were impractical if mining was to offer any tactical or strategic advantage. This is borne out by the actions of the belligerents during World War I, when conditions prevented enforcement. The stipulations of the original 1907 Hague Convention were never updated or amended. They remain, for all practical purposes, the basic international agreement on mine warfare in force today.

In summary, “The Hague Convention denied any warship the right to sink an unescorted merchant ship without first sending over a boarding party to decide if its cargo was contraband.

Pre-World War I
At this juncture, US Navy mine warfare capability as a significant weapon was limited both in producing mines as well as mine laying and sweeping mines. Great Britain was the resource for mine development. One of the reasons for the lack of acceptance of mines at this time and continuing into the 2o•h century came from an l 81h century perception of mines. As mines came into use, mine warfare was persistently perceived as a weapon for second-rate nations. It was not considered in line with traditional naval ways of fighting. Over time, this caused a continuing cyclic approach to supporting mines. In wartime, strong interest in all aspects of mines prevailed. Between wars, research, and attention lagged.

As a result of the successful mining in the Russo-Japanese War and the world-wide attention to the 1907 mining discussions at The Hague, the Navy requested Congress in 1907 for funds to convert certain cruisers of the Baltimore class (4500 tons, 20 knots) to mine depot ships. By June 1908, USS SAN FRANCISCO of this class was ordered refitted as a mine vessel and designated as a mine planter.

In 1909 with minimal ability to design and build mines, the U.S. Navy purchased the French-designed and-manufactured Sauter-Harle type designated as the US Naval Defense Mine Mark 2. This spherical mine with a contact inertia exploder and 175 pounds of guncotton came on the scene about 1909. Later in 1913, the French mine was used by the converted cruiser USS SAN FRANCISCO in mine laying and sweeping practice operations. Several years later USS BALTIMORE was modified and by 1915 conducted mining experiments in Chesapeake Bay and along the Atlantic coast. Later in 1918, USS BAL TIM ORE operated as a minelayer for four months in the 250-mile long North Sea barrage between Norway and Scotland.

Technical and chronological details of the evolution of the United States Navy sea mines starting with Mark I is found in Naval Weapons from 1883-to Present ( 1982) by Norman Friedman.

Other countries were following somewhat similar courses of action for mine warfare. France adapted cruisers of its Du Cha/ya class (4000 tons, 20 knots). For mine warfare, England modified the three cruisers Iphigenia, Alatona, and Thetis (3600 tons, 18 knots). Each cruiser was fitted for carrying I 00 mines. 26 Attention to countermeasures were also addressed by Germany, Great Britain, Italy and Austria in the years leading up to the World War I.

Germany was in the forefront of preparing for mine warfare by specially designing, building, and launching the mine depot ship Pelikan (2360 tons, 15 knots) in 1890. Similar Gennan ships, the Namilus and the Albatross, were launched in 1906 and 1907 ( 1970 tons, 20 knots). In 1910, Russia initiated the development of a minelayer submarine called the KRAB, capable of carrying up to 60 mines, and commissioned in 1915. Performance of the mine-laying equipment did not meet expectations.

Germany’s mine laying capability was such that two days after the start of the war, a minefield planted thirty miles off the English coast claimed a brand-new British cruiser. This and other success with mines and torpedoes is said to be attributable to the decade long thorough development and testing by Germany prior to the start of the war.

Mine developments prior to World War I in Europe included initial investigation of the magnetic influence mine. Counter-sweeping devices included mine wire cutters, snags, and explosive moorings.

At the beginning of the war, the U.S. Navy adopted a Vickers mine, the British Elia, licensed from Italy. The mine was equipped with a mechanically-triggered contact consisting of a 3 foot long protruding float and required the target ships to be within a few feet of the mine to be effective. Because of this contact mine’s distance limitation and overall )&ck of reliability, England’s immediate response was to bring 7,500 Russian mines left over from the Russo-Japanese War from the Pacific to the North Sea.

Later in a retrospective article, in June of 1934, the Naval Institute Proceedings commented about the capability of British mines in the early part of World War I. “These (mines) were so defective that German submarines, when pursued, would seek a British minefield and hide under for protection from attacking surface craft.” Mine range and reliability, both elusive requirements, were pursued in the wars of the 201h century.

In September of 1916, an unexploded Gennan E Hertz horn exploder contact mine was safely towed to shore and used for experiment and redesign. Consequently the redesigned British mine called the H2 became available in late 1917 in numbers that permit-ted offensive mining in enemy waters.

Subsequently, England used the first United States-designed mine, the Mark 5, a moored type with Hertz horns weighing a total of 1500 pounds with 500 pounds of TNT. Although the range for damaging enemy shipping was increased it was not an optimum distance. The Mark 5 was long lived and still in use in World War II.

Dardanelles and Gallipoli
A strip of water 38 -miles long by Y4 to I-mile wide is the access to Constantinople and the Black Sea from the Aegean Sea. In 1909, British war planning included strategies for taking control of the Dardanelles and having access to the Turkish capital and beyond.

In the latter part of 1914, Gennan Anny officers and men assisted Turkey in fortifying the waterway with mines and howitzers and gun fortifications. It is of interest that the mines came from diverse sources. Russian mines found floating in the Bosporus were salvaged, refurbished and replanted. While French mines from Smyrna were also used. In addition, Bulgarian mines left over from the second Balkan War in 1913 were sown. With a total of about 300 mines, the defensive mine fields when completed along the Dardanelles included contact and shore detonated mines for miles across the waterway.

A British plan to take control of the waterway was put into operation in March 1915. It envisioned that a naval force would transit the Dardanelles. The intensive mining, combined with the shore batteries and mobile howitzers that could reach the minefields, brought the intrusion to a stalemate. British minesweeping was countered at night by the use of Turkish spotlights and enemy mine reseeding. An early Turkish mining of 20 mines sank the three British battleships OCEAN, BOUVET, and IRRESISTIBLE. In summary, the British battleships were kept at bay by mobile howitzers and the minefield batteries while the contact minefields blocked passage.lo During the following ten months thousands of Allied troops tried unsuccessfully to advance using amphibious assaults along the Gallipoli peninsula with its awkward geography in a battle where relief, supplies or evacuation were impeded by the enemy mines and fortifications. With losses of more than 200,000 lives, British forces left in December. The total losses on both sides exceeded half a million. Integrated defensive mining was effective.

Germany’s Mine Laying Submarines
During the War Germany constructed more than 3 50 submarines. The submarine minelayers are of interest. Naval Institute Proceedings November/December 1915 reported on German submarine mine layers with airtight chambers where mines, primarily contact type, are placed ready to be sown. A delayed rising mine was also used. The stowage chamber is flooded and the mines are released and sink. The 110-foot-long UC-5, an UC-1 type, was one of the 114 minelayers. In a 9-month period on 29 patrols, the UC-5 laid 200 mines and sunk 29 ships before it grounded and was scuttled. The UC-5 ‘s record was characteristic of the minelayers.

World War I German Mine Laying Submarines

After the disaster at Gallipoli, Lord Herbert Kitchener, one of England’s highly-ranked and important Army officers and a significant figure in the struggle on the Turkish peninsula, was dispatched in mid-1916 to go to Russia to encourage that country to persevere in its struggle with Germany. He was en route aboard the cruiser HMS HAMPSHIRE when the naval vessel struck a mine laid by a German submarine and sunk in ten minutes. Kitchener was drowned.

British Mine Laying Submarines
Between 1912-17, the Royal Navy constructed 58 E-class submarines capable of operating in blue water. Six were converted into mine layers. These submarines were responsible for sinking about 100 enemy ships off the German coast. Subsequently, they were used for mine laying in the English Channel.

Responding to Mines
In late September 1914, weeks after the start of the War, England was taken aback by the loss of the three armored cruisers on the same day by a German submarine. This event and an increased sense of the danger from mines formalized England’s War Orders on January l, 1915 to take additional steps to be alerted to the presence of enemy submarines and mines. The orders provided prize money to trawlers and other vessels to report U-boat movements and participate in the capture or sinking of U-boats. Destruction of floating or moored enemy mines brought awards of £5 or £ 10. None of these measures proved effective.33 Early enemy success with mines and submarines was not anticipated. Preparedness for countermining was lacking and in the case of the enemy submarine, there was no antisubmarine device to detect its presence when submerged.

Later in the war, the United States like England would have mines planted by U-boats along some of its seaports to interdict commercial shipping. The ports required mine clearing. As the war began the United States minesweeping force consisted of only three converted fleet tugs and a few fishing trawlers.34 Eventually, defense involved ten tugs on permanent minesweeping. Later the force was augmented by lighter mine sweeping equipment on destroyers and torpedo boats.

After United States entry into the war, a steel net was sunk across the Verrazano Narrows between Brooklyn and Staten Island to keep German submarines out of the inner harbor. German submarines planted mines around Sandy Hook. and 16 tugboats based at Staten Island were turned into minesweepers. “Working in pairs, they swept the ocean every day for I 00 miles out from Sandy Hook, finding and exploding a large number of floating mines.”

Germany’s early, continuing, and expanding submarine successes shifted Allied naval efforts to a stronger defensive role. These efforts bought about the development and implementation of simple hydrophones for submarine detection along with TNT depth charges, sea mines, and, later in the war, broad convoying of merchant ships. Each contributed to eventual victory.

Sea Mines and the North Sea Barrage
Plans for mining the North Sea from Norway to the Orkneys, off Scotland, to deter the U-boats en route to the Atlantic were under consideration as early as 1915. In 1913, a British war plan considered mining the Heligoland Bight off Germany’s North Sea coast and the Strait of Dover with 50,000 mines. This was dropped because of cost. The extreme merchant shipping losses brought it to the fore again in 1917. The ship losses for April 1917 escalated to 900,000 tons.

This was a very critical time, as the German submarine war against unprotected merchant shipping was succeeding. Ventures against the U-boats irrespective of the approach always demanded inordinate support including manpower, equipment, and financing. n the spring of 1917, two concepts, each a huge undertaking, were competing for immediate implementation and support. A consensus for greater support for merchant ship convoying to stem the U-boat was finally reached at this time. The barrage was also approved but with some restraint. Before long, the success of convoy enhancement became evident.

As planned the length of the barrage was 250 miles with a width of 15 to 20 miles. Initial estimate of the number of mines required as 120,000. This required number was substantially reduced with the development of the United States MK 6 (moored contact type mine), designed around a new galvanic firing device. Working at the Naval Torpedo Station in Newport, Rhode Island, Ralph C. Browne invented the mine’s firing device.36 The MK 6, in addition to Hertz horns, was equipped with two 70 foot vertical underwater antennas, one held above the mine by a float and the other the mooring cable below attached to the mine’s anchor. Actual contact of the mine by the enemy vessel was not necessary. Contact by the U-boat with either of the mines vertical antennas produced galvanic action and initiated the explosion.

Enemy vessel contact with the Hertz horns provided an additional opportunity for an explosion.

The MK 6 vertical antennas above and below the mine substantially increased vertical and horizontal coverage and decreased the number of mines needed for a given area. Further, it did not require specialized minelayers and released mine layers for other assignments. The mine with 300 pounds of TNT was dropped from rails off the stern of surface vessel in water 30 to 3000 feet deep. Long-lived it was widely used from 1917 to about 1985. British mine planting began in March and that of the United States in June of 1918 and continued on until October as the war was moving to an armistice. Large mine laying ships could lay 5,000 mines in a four-hour operation.37 Cruisers USS SAN FRANCISCO and USS BALTI-MORE converted to mine laying were both assigned to the North Sea barrage and achieved laying thousands of mines in a few hours, Premature explosions of the MK 6 did not portend success. The United States contracted with automobile manufacturers to manufacture 6,000 mines a week. The United States produced, shipped and planted 56,611 mines and England planted 16,300. An estimate of the ost of the barrage in 1918 dollars was $40 million.

The barrage is deserving of historical attention both as an important high-seas mining operation and an incredible engineering and logistical challenge achieved in a short time. However, as commented in 1966 by Philip K. Lundeberg, “it proved less than an unqualified success.” Mine laying operations started in June 1918 (six months prior to the end of the War). Lack of performance may be attributed to the haste of mine development and manufacture and the results of the barrage on a longer war are unknown.

Another and darker view of the barrage and the uncertainty of its effects was presented by “Submarine Mining, Orphan Child of the Service” Naval Institute Proceedings, 1934. In addition to pointing out the Navy’s cyclic interest in sea mines, the article raised questions regarding the barrage’s overall viability. As noted above, the barrage was only completed a few months before the end of the war and its long-term capability was not tested. From the article.

“It is a fact that only 43 percent of the mines were on duty when, after the war, the mine sweepers cleared the fields and this was only a matter of months after they were laid, whereas they should have stood guard for several years … who classed the venture as “a bluff that worked”.

Magnetic Mines
By 1918, British researchers developed and implemented the magnetic influence mine. The mine, the concrete-cased M-sinkers resting on the bottom, detonated when they sensed a ship’s magnetic signature. A bottom location provided the necessary constant magnetic reference to be able to detect the presence of the magnetic steel hull of a vessel or submarine. Features of the magnetic mines included no requirement for a mooring cable. Further magnetic mines resting on the bottom were difficult to sweep. Magnetic mines introduced late in World War I needed further development. During the inter-war years, enhancements made them a better weapon and both sides in World War II widely and effectively used them.

With the war ending in the first year of deployment, 1918, and the poor reliability of the newly developed magnetic mine, the overall otential of the weapon was not fully understood or appreciated. In October of 1939 the First Sea Lord, Admiral Dudley Pound, wrote regarding the magnetic mine, “It is really the limit that after knowing about magnetic mines since the last war, no practical method of dealing with them had been evolved.”39 During World War JI degaussing (demagnetizing) ships was developed to reduce ship’s magnetic signature and sensitivity to magnetic mines. This counter-measure provided relief at a cost of time and money ($300 million).

The Royal Navy in April 1918, laid early M-sinkers off Zeebrugge, Belgium on the North Sea in conjunction with an attempted destruction of the U-boat pens. The mining at Zeebrugge also involved the British H2 mentioned above, an improved 1917 design based on an successful German contact mine configuration.40 During 1918, 11 of the 31 U-boats lost by the Flanders flotillas were claimed by Channel minefields with a possible additional 11 losses from the same weapon.41

Use of magnetic mine is also cited in an article by Frank Reed Horton who wrote, “During the First World War, I served as an ensign in the United States Navy aboard a minesweeper in the North Sea. Our ship and its partner exploded more than 1,000 magnetic mines.” Magnetic mines, in use late in World War I and requiring improvement, improved during the inter-war years and were widely and effectively used as an important weapon by both sides in World War II.

At the time of the Annistice in November of 1918, the mine was a comparatively inexpensive weapon with a proven success in naval warfare. The mine was responsible for the highest attrition of warships, compared with that of all other surface weapons combined in that war. In World War I, more than 300,000 mines sank or damaged more than 950 Allied and Central Power, warships, merchantmen, and submarines.

Allies lost 586 merchant ships and 87 warships not including I 52 small patrol boats and minesweepers. The Central Powers’ losses to mines included 129 warships, excluding an unknown number of merchant ships and submarines. Once again, the total ship damage in WWI from mines was far greater than that by gunfire and torpedoes.

The effectiveness of the submarine, the torpedo, and the mine almost from the first days of World War I was not anticipated. Countering each became an all-consuming task for both sides for the entire war. In the almost 90 years since the Armistice, means to counter the submarine and the two weapons continues to confound those involved.

A kind of consensus regarding the lack of preparation or anticipation of the submarine’s guerre de course, the mine, and torpedo in some instances was based on the lack of fiscal resources in peacetime to meet the requirements of the military. In the case of Great Britain, attention to preparing for offensive high seas battleship or dread-naught encounter seems to have precluded adequate support for alternative weapons like the mine and torpedo. Throughout the war, the inexpensive mine inhibited battleship maneuvers or even putting to sea in some instances.

Historical evidence shows that sea mines, depth charges and submarines at some point in their introduction received slow acceptance as they were perceived as being a weapon for nations with small or inferior navies. In the l 91h century, acceptance of steam versus sail in the United States Navy was not unanimous.

During most of the first half of the 201h century, the concentration on capital-ship construction with the attendant cost and crew size was often steep competition for small ship needs and attention to new naval technologies. In retrospect, small-specialized ships for convoys, mining and countermining were frequently lacking. However, the role of mines in World War II, the Korean War, the Vietnam War, and the Iraq Wars have each brought careful attention to sea mines and their defensive and offensive roles as the weapons that wait.

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