A Sperrbrecher (German
German language
German is a West Germanic language, related to and classified alongside English and Dutch. With an estimated 90 – 98 million native speakers, German is one of the world's major languages and is the most widely-spoken first language in the European Union....

; informally translated as "pathfinder" but literally meaning "minefield breaker"), was a German
Nazi Germany
Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...

 auxiliary ship
Auxiliary ship
An auxiliary ship is a naval ship which is designed to operate in any number of roles supporting combatant ships and other naval operations. Auxiliaries are not primary combatants, although they may have some limited combat capacity, usually of a self defensive nature.Auxiliaries are extremely...

 of the Second World War that was intended to serve as a type of minesweeper
Minesweeper (ship)
A minesweeper is a small naval warship designed to counter the threat posed by naval mines. Minesweepers generally detect then neutralize mines in advance of other naval operations.-History:...

, by sailing ahead of other vessels through minefields, intending to detonate any mines in their path. Also used as anti-aircraft ships, the Sperrbrecher suffered heavy losses in the war.

Operational history

Officially designated as 'Special Purpose Merchant Ships', although termed by the Royal Air Force
Royal Air Force
The Royal Air Force is the aerial warfare service branch of the British Armed Forces. Formed on 1 April 1918, it is the oldest independent air force in the world...

 as 'Heavy Flak Ships', the Sperrbrecher were converted from merchant ships for their special role, were primarily crewed by merchant seamen, and often had their cargo holds filled with buoyant material to aid in flotation in case of hitting a mine. The bows were also strengthened. Ships converted to the Sperrbrecher type were usually fitted with heavy anti-aircraft armament, and often carried barrage balloons.

The primary use of the Sperrbrecher was to escort other vessels through cleared paths in defensive minefields, for the purpose of detonating any mines that might have strayed into the passageways. In addition, the ships of the Sperrbrecher type would, early in the war, be used to clear suspected enemy minefields by simply sailing through them. Even with the strengthened hull and buoyant material, however, the ships suffered heavy losses in this role, and with the advent of acoustically and magnetically fused mines, this role became ineffective. Later in the war the Sperrbrecher type ships were used to escort U-boat
U-boat is the anglicized version of the German word U-Boot , itself an abbreviation of Unterseeboot , and refers to military submarines operated by Germany, particularly in World War I and World War II...

s in and out of harbour.

Due to their heavy, dual purpose armament and respectable fire control a Sperrbrecher was also a capable surface combattant, significant enough to deter a RN escort destroyer from engaging for fear of "a bloody nose".

In an attempt to counter newer, magnetically fused mines, some ships of the Sperrbrecher were equpped with a large electromagnet
An electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric current. The magnetic field disappears when the current is turned off...

 fitted in their bows. Referred to as the VES system, this was intended to detonate magnetic mines well clear of the vessel, the design specifications calling for a distance of 500 yards (457.2 m) from the hull at detonation. However, careful military intelligence
Military intelligence
Military intelligence is a military discipline that exploits a number of information collection and analysis approaches to provide guidance and direction to commanders in support of their decisions....

 work by the Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

 resulted in a method to defeat this method of minesweeping, sinking several Sperrbrecher through the careful fusing of mines laid as traps, their fuses desensitised to be activated only when the sweeping vessel was directly above them.

Over one hundred vessels, mostly merchant ships of around 5000 tonnes (5,511.6 ST) and larger displacement, were converted to serve in the Sperrbrecher role, and it is estimated that around 50 percent of the vessels converted were lost during the war.

During World War II only one commander received the Knight's Cross of the Iron Cross
Knight's Cross of the Iron Cross
The Knight's Cross of the Iron Cross was a grade of the 1939 version of the 1813 created Iron Cross . The Knight's Cross of the Iron Cross was the highest award of Germany to recognize extreme battlefield bravery or successful military leadership during World War II...

 for services on a Sperrbrecher. Korvettenkapitän of the Reserves
Military reserve force
A military reserve force is a military organization composed of citizens of a country who combine a military role or career with a civilian career. They are not normally kept under arms and their main role is to be available to fight when a nation mobilizes for total war or to defend against invasion...

 Karl Palmgreen
Karl Palmgreen
Karl Palmgreen was a Fregattenkapitän of the Reserves with the Kriegsmarine during World War II and a recipient of the Knight's Cross of the Iron Cross with Oak Leaves...

received the award on 3 August 1941 as commander of Sperrbrecher IX and I.

Following the end of the war, some of the surviving Sperrbrecher were converted back to merchant duties, and some of these vessels continued in their more peaceful service until the 1970s.
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