The most common U-boat attack during the early years of the war was conducted on the surface and at night. This period, before the Allied forces developed truly effective antisubmarine warfare tactics, which included convoys, was referred to by German submariners as "die glückliche Zeit" or the First Happy Time. The U-boats' main weapon was the torpedo, though mines and deck guns (while surfaced) were also used. By the end of the war, almost 3,000 Allied ships (175 warships; 2,825 merchant ships) were sunk by U-boat torpedoes. Early German World War II torpedoes were straight runners, as opposed to the homing and pattern-running torpedoes that became available later in the war. They were fitted with one of two types of pistol triggers impact, which detonated the warhead upon contact with a solid object, and magnetic, which detonated upon sensing a change in the magnetic field within a few meters. One of the most effective uses of magnetic pistols would be to set the torpedo's depth to just beneath the keel of the target. In this way, even large or heavily armored ships could be sunk or disabled with a single, well-placed hit. Initially, the depth-keeping equipment and magnetic and contact exploders were notoriously unreliable. This was most evident in Operation Weserübung, the invasion of Norway, where various skilled U-boat commanders failed to inflict damage on British transports and warships because of faulty torpedoes. The faults were largely due to a lack of testing. The magnetic detonator was sensitive to mechanical oscillations during the torpedo run, and to fluctuations in the Earth's magnetic field at high latitudes.
These early magnetic detonators were eventually phased out, and the depth-keeping problem was solved by early 1942 with improved technology. Later in the war, Germany developed an acoustic homing torpedo, the G7/T5. It was primarily designed to combat convoy escorts. The acoustic torpedo was designed to run straight to an arming distance of 400 m and then turn toward the loudest noise detected. This sometimes ended up being the U-boat; at least two submarines may have been sunk by their own homing torpedoes.Additionally, these torpedoes were found to be only effective against ships moving at greater than 15 knots (28 km/h). The Allies countered acoustic torpedoes with noisemaker decoys such as Foxer, FXR, CAT and Fanfare. The Germans, in turn, countered this by introducing newer and upgraded versions of the acoustic torpedoes, like the late-war G7es, and the T11.
However, the T11 did not see active service. U-boats also adopted several types of "pattern-running" torpedoes that ran straight out to a preset distance, then traveled in either a circular or ladder-like pattern. When fired at a convoy, this increased the probability of a hit if the weapon missed its primary target.Mint German WWII Kriegsmarine U-boat Torpedo Timer Stop Watch by Hanhart" is in sale since Sunday, April 4, 2021. This item is in the category "Collectibles\Militaria\WW II (1939-45)\Original Period Items\Germany\Personal, Field Gear". The seller is "premierrelics" and is located in Bloomington, Illinois. This item can be shipped worldwide.