could not produce enough food to feed all its people.
needed raw materials from abroad to run its industries.
If the merchant Navy could not bring these things into
Britain by sea, the war would be lost.
fall of France allowed U-Boats to operate far into the
Atlantic from French ports.
Nazi shipyards produced about 20 new U-boats a months,
and British merchant shipping losses grew.
After summer 1940, the U-boats attacked in large
‘wolf-packs’ – when a U-boat came across a convoy, it
would radio its position to a number of other submarines,
which would close in on the convoy.
Then they would wait until nightfall and make surface
attacks in numbers.
On 18 October 1940, a pack of 6 Nazi U-boats attacked
slow convoy SC–7, sinking 15 ships in 6 hours.
Next day, reinforced by three more U-boats, the pack
attacked the 49-ship convoy HX-79, sinking 12 ships in one
The Royal Navy did not have enough ships to protect the
convoys properly. In
November 1940 convoy HX–84 (37 ships escorted only by the
armed merchant cruiser HMS Jervis Bay), was attacked by
the Nazi battleship Admiral Scheer.
Completely outgunned (her shells did not even reach the
Nazi ship) the Jervis Bay attacked the Admiral
Scheer to give the convoy time to escape – the Jervis
Bay and five merchant ships were sunk.
The USA tried to help Britain.
In August 1940 the US gave Britain 50 destroyers in
exchange for Atlantic naval bases, and, after August 1941, by
an agreement called the Atlantic Charter which
Roosevelt made with Churchill, convoys were defended by the US
had little effect.
Losses were huge. The worst period was from the beginning of 1942 to
March 1943 when 7 million tons of merchant shipping was sunk. In July 1942, 143 ships were sunk in a single month,
and in November 1942, 117 ships were lost.
things helped the Allies to stop the U-boat menace.
work of the British codebreakers at Bletchley Park in
deciphering the German Enigma code was vital in
giving the Allied navies the edge in the Battle of the
Atlantic. In February 1942, however, the German code was
improved, resulting in ‘the Drumbeat crisis’ when
shipping losses were their greatest – until March 1943,
when the German code was again broken.
had been invented before World War I, but after 1942 the
US Navy Department developed ‘console sonar’ which
could plot accurate bearings using an echo ‘ping’. Training of sonar operators was also improved.
was improved so that U-boats could even be detected in bad
British developed HF/DF (‘huff-duff’), whereby
U-boats’ positions could be worked out from their radio
aircraft carriers were sent to patrol the Atlantic, and
this extended air cover to the whole route convoys took.
depth-bombs were developed so that planes could attack
U-boats under the water.
called Hedgehog and Squid were developed
which allowed attack ships to catapult depth-charges up to
300 yards in front of the ship.
Allies set up hunter-killer groups of ships, including one
aircraft carrier with a number of destroyer escorts, to
hunt down and sink U-boats.
turning point was slow Convoy ONS–5 (April–May 1943), when
a convoy of 43 merchantmen escorted by 2 destroyers and a
frigate was attacked by a wolf-pack of 30 U-boats.
Although 13 merchant ships were sunk, the U-Boats were
detected by HF/DF, six U-boats were sunk by patrol-boats or
Allied aircraft and – despite a storm which scattered the
convoy – the merchantmen reached the protection of
land-based air cover causing Admiral Dönitz to call off the
It was the end of the U-Boat menace – 37 U-Boats were
lost in May 1943, and 34 in July.
The RAF was able to intercept and sink many U-boats as
they left harbour.
The Nazis gave their U-boats better anti-aircraft guns,
and invented a device called Snorkel (which allowed U-Boats to
refresh their air without surfacing).
‘Bottoming’ tactics allowed U-boats to avoid
detection from sonar and radar.
However, after May 1943, the U-boats were on the
defensive, and Allied shipping losses fell significantly.
Nevertheless, it must be questioned whether the Allies
‘won’ the Battle of the Atlantic – between 1939 and
1945, 2,753 Allied ships were sunk (gross tonnage 14.5
million) at a cost of 783 Nazi U-boats.