G7es torpedo
The G7es or Zaunkönig T-5 (wren
The wrens are passerine birds in the mainly New World family Troglodytidae. There are approximately 80 species of true wrens in approximately 20 genera....

in German) was a torpedo
The modern torpedo is a self-propelled missile weapon with an explosive warhead, launched above or below the water surface, propelled underwater towards a target, and designed to detonate either on contact with it or in proximity to it.The term torpedo was originally employed for...

 employed by German
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 U-boats during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. It was known as the GNAT (German Navy Acoustic Torpedo
Acoustic torpedo
An acoustic torpedo is a torpedo that aims itself by listening for characteristic sounds of its target or by searching for it using sonar. Acoustic torpedoes are usually designed for medium-range use, and often fired from a submarine....

) to the British.


The forerunner of the T-5 was the G7e/T4 Falke , codename "Falcon," which was introduced in March 1943, but only fired by three U-boats by September of that year when the G7es (which was faster, had more range, possessed a magnetic fuze
Fuze Beverage, commercially referred to as just Fuze , is a manufacturer of teas and non-carbonated fruit drinks enriched with vitamins. Currently the brand consists of five vitamin-infused lines: Slenderize, Refresh, Tea, Defensify, and Vitalize...

 and could also be equipped with a percussion fuze) became available.

The torpedo was electric and had an effective range of 5700 meters at a speed of 24 knots (44 km/h). This torpedo employed passive acoustic homing to find its target, becoming active after a straight run of 400 meters. The homing mechanism consisted of two hydrophone receivers which sensed the sound waves of ship propellers and altered the direction of the rudder via a electropneumatic device.

There were two main variants:
  • A flat-nosed version which contained two sets of magnetostriction
    Magnetostriction is a property of ferromagnetic materials that causes them to change their shape or dimensions during the process of magnetization. The variation of material's magnetization due to the applied magnetic field changes the magnetostrictive strain until reaching its saturation value, λ...

  • A round-nosed version which contained two magnetostriction hydrophones inside a funnel-shaped baffle.


The 400 meter limit was employed for safety reasons, even though there were at least two instances of U-boats (U-972 in December 1943 and U-377
German submarine U-377
German submarine U-377 was a Type VIIC U-boat of the German Kriegsmarine during World War II. The submarine was laid down on 8 April 1940 at the Howaldtswerke yard at Kiel, launched on 15 August 1941, and commissioned on 2 October 1941 under the command of Kapitänleutnant Otto Köhler.U-377 was...

 in January 1944) sinking after being hit by their own torpedo. This risk was later mitigated by requiring submarines to dive to 60 meters and go completely silent after launching acoustic torpedoes.

The first 80 T-5s were delivered on 1 August 1943, and the weapon was first used in September. Despite some success, in particular sinking destroyers and corvettes, the T-5 often detonated behind the enemy ship because the acoustic steering was very imprecise. This was particularly evident at its first large-scale use from 20 to 24 September 1943 in the attacks on convoy ON-202. The commanders reported a number of torpedo strikes and recorded the sinking of nine commercial steamers and twelve escort ships after the battle. In fact only six merchant ships and 3 escort vessels, a destroyer, a frigate and a corvette were sunk. A total of 640 T-5s were fired in combat, sinking 45 ships. The T-5 was countered by the introduction by the Allies of the Foxer
Foxer, was the codename for a British built acoustic decoy, used to confuse German acoustic homing torpedoes like the G7es torpedo during the Second World War. A US version codenamed FXR was deployed in 1943. A Canadian version was also built called the CAT...

noise maker.

The T-5 was nicknamed Zerstörerknacker (destroyer cracker) by the German submariners, as it was especially used against convoy
A convoy is a group of vehicles, typically motor vehicles or ships, traveling together for mutual support and protection. Often, a convoy is organized with armed defensive support, though it may also be used in a non-military sense, for example when driving through remote areas.-Age of Sail:Naval...


Further reading

  • Valentin Pikool, a Soviet Novelist talked about G7es torpedo in one of his historic novels.

External links

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