Battle of the atlantic

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Grand Admiral Karl Doenitz had been a U boat
captain in WW1. He masterminded Germanys naval
blockade strategy in the 1930s and urged Hitler
to build a fleet of 300 u boats for future war
against GB. Hitler ignored his advice,
concentrating on the development of bomber fleets
and tanks. This proved to be a strategic mistake
on Hitlers part as U boats were far more precise
and effective than bombers.
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A German U-boat. The technology had not greatly
advanced since WW1.
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Contrary to popular belief, U-boats only dived
during an attack. Most of the time on patrol they
operated on the surface. The diesel engines
needed oxygen. Under water the U-boats operated
on electric power from batteries re-charged by
the diesel engines when on the surface.
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The fall of France in June 1940 was a disaster
for GB as Germany could now use the Atlantic
coast of France to build U boat bases and strike
out in to the sea lanes of the Atlantic.
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The ancient French port of La Rochelle became a
key German U boat base and was heavily bombed by
the RAF (to no effect). The town was restored
after WW2.
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The Germans constructed U boat pens at Lorient
and St Nazaire also. Seen here they featured 7
foot walls and roofs made up reinforced concrete.
RAF bombs merely scratched the surface.
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La Rochelle today
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Inside a U boat pen
Safe from aerial attack U boats could be refitted
and repaired.
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1940-43

• Between 1940-43 the German U-boats became deadly
  effective. British and American shipping losses
  far out-stripped their ability to seek out and
  destroy the U-boats.
• Allied aircraft had limited range over the vast
  expanse of the Atlantic and had only primitive
  detection systems.
• U-boats hunted in packs (known as wolfpacks)
• When a convoy was sighted by one U-boat, the
  position would be transmitted to other U-boats
  which would move in for the kill. This technique
  was extremely effective.
• Britain relied on shipments of food, oil,
  materials and weapons from Canada and the USA.
  The U-boats threatened Britain with starvation.

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Rationing
Imported foodstuffs such as meat, sugar and wheat
were strictly rationed. Tobacco imports were also
considered a matter of national survival in an
era when a majority of the population were
smokers !
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Land girls in Paddock Wood
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Agricultural output was vital.
The WLA was no mere propaganda effort. Boosting
food output required the mobilisation of the
female workforce to free up young men of fighting
age to enlist.
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The food front or kitchen front was rightly
seen as a matter of national survival
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The Convoy system
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One of the most dangerous jobs in World War Two
was that of the merchant seamen. Their survival
chances were slim if their ship went down in the
icy waters of the North Atlantic Ocean.
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A US oil tanker ablaze in 1942
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Defeating the U-boats

• May 1943 was the turning point in the Battle of
  the Atlantic.
• For the first time, German U-boat losses began to
  outstrip Allied shipping losses.
• A number of technological advances made this
  victory possible.

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Breaking the U boats coded messages
In World War Two the German U boats used an
encryption machine called ENIGMA to transmit
messages. It had billions of possible settings
and was seen as unbreakable.
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Alan Turing was a British mathematical genius who
led the code-breaking effort and devised the
first electronic brain to help speed up the
billions of calculations needed to break the
code.
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Station X or Bletchley Park
The British code breakers at Station X built
their own machine to crack the code. Colossus is
seen by some as the worlds first computer
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Station X now a museum.
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The Liberty Ships
American shipyards began to mass produce a bulk
cargo ship named the Liberty Ship. It was
pre-fabricated for quick assembly. American
shipyards could replace them faster than the
U-boats could sink them. This war of industrial
attrition favoured the American economy
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The Ugly Duckling
Simple of design, functional and easy to build
the Liberty Ship was a decisive factor in the
defeat of the U-boats. They did not require
highly skilled workers to build and one ship yard
laid the keel of one ship in a record time of
three days. Only American mass production
techniques could achieve such feats of
productivity.
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American industrialist Henry Kaiser led a group
of six companies which mass produced 2,751
Liberty Ships in just four years.
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Against such odds the German U-boat campaign
began to falter in 1943.
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The Cavity Magnetron
An electronic marvel that allowed for the
development of high frequency and accurate
airborne radar.
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Anti-submarine devices
Exploding under-water bombs or depth charges
were dropped on suspected U-boat
positions. Using better radar detection devices
the use of depth-charges became more effective.
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The Hedgehog (1943)
A highly effective anti-submarine weapon that
laid a ring of explosives around a U-boat,
increasing the chances of a kill.
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The Leighlight, a powerful searchlight fitted to
anti-submarine aircraft in 1942
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The American B24 Liberator bomber
A long range aircraft ideally suited to
anti-submarine warfare.
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US mass-production.
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Grand Slam A bomb large enough to penetrate
the thick concrete roofs of the U-boat pens. Not
used until 1945
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The Farge U boat pen after a direct hit from a
Grand-Slam bomb in early 1945
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Allied shipping losses (tons)
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Defeat of the U boats
Allied shipping losses
May1943tipping point
U-boat losses