The Third Reich had the biggest submarine fleet
during World War II and was a major part of the
Battle of the Atlantic. This was because of the
Treaty of Versailes. which restricted the building
of battleships to six (of less than 10,000 tonnes
each) 12 destroyers and six cruisers.
U-boats were very good in destroying Allied shipping,
from the Atlantic coast of the United States and
Canada to the Gulf of Mexico, and from the Arctic
to the West and Southern African coasts, and as
far East as Penang.
Sir Winston Churchill the United Kingdoms Prime
Minster wrote saying the only thing that really
frightened me during the war was the U-boat peril.
Although later evidence collected showed that 98%
of British ships in the first 28 months of the war
crossed without any damage.
U-boats spent most of their time on the surface
running on diesel engines, as speed and range was
very restricted while underwater as they had to
run on battery power, and only diving when under
attacked or daytime torpedo strikes which was very
rare. Most attacks happened at night and on the
surface until allied forces developed a antisubmarine
warfare tactics known as (ASW) which was very effective
German U-boat commanders called this a happy time.
The U-boat was a sophisticated launch platform for
its main weapon was the torpedo. World War II torpedoes
had many limitations and suffered from this, as
they could only be launched from periscope depth
or on the surface and until later in the war they
were unguided going in straight lines, until it
hit an object or run out of power.
They were fitted with two types of fuses, which
detonated the warhead on impact with a solid object
and the other magnetically sensing a large metal
object.
When using magnetically warhead torpedoes the commander
would know the targets ships draft (how low its
keel sits in the water) and set the torpedoes depth
so that it went just underneath, detonating the
magnetic fuse. The explosion would make a temporary
gas bubble underneath the unsupported keel, which
would then cause a split. As a result large or heavy
-armoured ships could be sank or damaged in one
single hit if hit in the right place. However, in
reality magnetic fuses and depth-keeping equipment
were both very unreliable in the early stages of
the war. Torpedoes would run at wrong depths detonate
early, or bounce harmless off the targets hull.
Commanders lost faith and it took sometime to put
these problems right.
Later on in the war. The Third Reich then designed
and developed an acoustic homing torpedo which run
to an arming distance of 400meters and then zero
in on the loudest noise it heard. This could sometimes
be the U-boat itself, and has at least sunk two
submarines of their own. U-boats also had torpedoes
that had pre-set distance to run and then either
a circular or ladder like pattern, so that when
fired at a convoy this would increase the chances
of a hit in case the torpedo missed the main target.
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