The Battle of the Atlantic

26.04.2018 |

Episode #7 of the course Ten turning points of World War II by Patrick Allitt


Britain could not feed itself. Dependence on food imports in peacetime was fine but became dangerous in wartime, especially against an enemy that was powerful at sea.

Germany’s surface fleet could not match Britain’s, but the German navy was strong in submarines. Earlier in the 20th century, during World War I, they had upset the conventional wisdom about naval power, showing that to be small and stealthy could be as deadly as being massive and bristling with big guns. Dozens of submarines could be built for the price of one battleship, and a battleship could be sunk by a skilled and daring sub commander.

Experience in World War I had shown Britain that individual freighters crossing the Atlantic from Canada and the USA were vulnerable. They had switched to a convoy system and took it up once more at the start of World War II. Convoys moved at the speed of the slowest ship, but now the freighters and tankers, bringing food, munitions, and oil to Britain, were surrounded by purpose-built escort ships, which improved as the war went on.

Equipped with ASDIC, an echo-location system, and armed with depth charges that could crush a submarine’s hull when they exploded close by, they improved the defenders’ odds. Forward-firing anti-submarine weapons like “hedgehog” (from 1942) improved the Allies’ countermeasures. First, British and Canadian, then American, captains learned by trial and error how to identify and then intercept the submarines.

On the other hand, the German conquest of France in 1940 enabled Germany to station submarines along the French west coast so they would not have to run the gauntlet of the narrow English Channel at the start and end of each mission. Being several hundred miles further west than German ports, this also meant that they could range further into the Atlantic and stay out on patrol longer. Talented submarine captains sometimes risked night attacks on the surface. The leading submarine “ace,” Otto Kretschmer, sank 47 Allied ships before finally being captured from his sinking ship, U-99, in 1941.

The balance of power between attackers and defenders in the North Atlantic shifted from month to month as the war went on, as each side’s technology improved, as each side broke the other’s codes, and as the Germans worked on sending concentrated “wolf packs” of submarines against convoys. Between mid-1940 and early 1941, the Germans had most of the initiative and struck deadly blows against the convoys, with submarines sinking 60% of the ships in Convoy SC-7, for example, in October 1940.

They also deployed their few battleships against convoys, culminating in the last voyage of the giant Bismarck, which destroyed the British battleship, HMS Hood, but was finally run down and sunk by the Royal Navy in May 1941. Improvements in escort technique swung the convoy battle in the Allies’ favor after that, and German battleships were withdrawn as simply too vulnerable.

Once America joined the war, Germany mounted a damaging new offensive, “Operation Drumbeat.” Submarines stationed just off the US coast attacked freighters that were silhouetted against the bright lights of American cities, sinking over 300 ships in early 1942. The worst time of the entire battle for the Allies came in March of 1943, when they lost 82 ships while destroying only twelve submarines. Britain, short of everything, especially fuel, came to the brink of collapse.

It was able to recover in the following months because of increased long-range air support, more and better escort ships, and new techniques for killing the U-boats. By late 1943, the Allies had regained, and never subsequently lost, the initiative, enabling them to ship the immense quantities of materials to Britain that would be needed for the planned invasion of mainland Europe.

Tomorrow, we will see how the naval balance of power shifted in the Pacific theater of war when the US Navy, recovering from the shock of Pearl Harbor, won a decisive victory in the Battle of Midway. It was the world’s first naval battle dominated by aircraft and aircraft carriers rather than by big ships confronting one another directly.


Recommended book

Bloody Winter by John M. Waters Jr.


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