What image do you have of Winston Churchill as he led Britain during the Second World War? Most people would say positive things like ‘steadfast’, ‘unflinching’, ‘courageous’, etc., few would mention the word ‘afraid’. Yet there was one thing which worried him more than any other, in his own words ‘…the only thing that ever really frightened me during the war was the U-boat peril.’ And Churchill had every right to feel afraid. The route across the Atlantic was Britain’s lifeline, and Germany’s best hope of defeating the island nation would be by winning the Battle of the Atlantic.

Britain relied heavily on merchant ships carrying supplies of raw materials, food, troops, and military equipment from America. If the convoys had failed to get through Britain would most likely have been starved to the brink of surrender; her badly equipped armies, lacking tanks and weapons built in America, would have been overrun; it would have been impossible to transport land forces to North Africa, the Mediterranean, or across the English Channel on D Day; and it would have been impossible for the British to blockade the Axis powers in Europe. In short, if German U-boats had reigned supreme in the Atlantic then Hitler would, in all likelihood, have won the war.

The first phase of the Battle of the Atlantic lasted from the outbreak of war in 1939 until the British retreat from Dunkirk in June 1940. This was a time which saw the British and French with the upper hand, establishing a long-range blockade on German merchant ships. But after the German victories in northern Europe in 1940 and the entry of Italy into the war, Britain lost the support of the French navy. It was a difficult time; as well as the loss of the French ships Britain also suffered losses in the retreats from Norway and Dunkirk, losses which cut the British merchant fleet to almost half of its former size at the critical moment when Germany was acquiring naval bases on the Atlantic coast of France which made it easier for them to attack Allied shipping in the Atlantic; bases such as the one at Saint Nazaire. The attacking forces had the support of long-range Kondor aircraft which carried out reconnaissance for the U-boats and also attacked Allied shipping. Between the fall of France in June 1940 and the end of the year German U-boats sank three million tons of Allied shipping. To make matters worse, the Axis powers in the Mediterranean made the route through the Suez Canal so dangerous that British merchant ships had to take the much longer route around the Cape of Good Hope. The situation, which was so dire for the Allies, appeared more hopeful for the Germans who believed that it would only be a matter of time before they would knock Britain out of the war by attacking her trade. (The Germans estimated that they would have to sink 150 merchant ships a month to starve Britain into submission).

The German U-boats hunted in ‘wolf packs’ which were faster than the convoys and had the advantage of being able to see without being seen. The merchant convoys were relatively safe in either British or American waters where they could receive fighter cover, but were much more vulnerable in the mid-Atlantic where German submarines reigned supreme. During the autumn and winter of 1940-41 German U-boats had great successes supported by surface ships and planes. But Britain hung on with the help of Canadian naval and air forces so that, by May 1941, a system of fully escorted convoys was in place. The position for Britain was eased further with the ‘Destroyers for Bases’ deal in which America, although not yet in the war, provided more than 50 old World War I destroyers in return for 99-year leases for bases in the Caribbean. New lightly-armoured and much faster ships called corvettes began to accompany the convoys; with their ASDIC (which helped them to hear submarines underwater) and their arsenal of depth charges they began to make a difference. Close to shore new planes like the Sunderland were able to give better air cover as a submarine had to be close to the surface to fire its torpedoes and so became a sitting target for the planes. Allied losses began to fall at last, particularly when the convoys sailed during bad weather as the U-boats could not fire their torpedoes in a heavy swell.

Things changed again after Pearl Harbor and America’s entry into the war. US ships were re-deployed to the Pacific to face the Japanese threat, and the Germans found that shipping on the American east coast in early 1942 was unguarded. The situation led to a rise in Allied merchant shipping losses in the first half of 1942 with disastrous results – in those six months more tonnage was lost than in the entire preceding two and a half years. To make matters worse, the U-boat packs were ranging across the South Atlantic as well, targeting the shipping lanes from Asia and the Middle East, while Allied convoys to Russia were also suffering heavy losses.

It was Canada who once again came to the rescue, providing escorts for the North Atlantic convoys while America underwent a huge ship-building programme so that, by the autumn, they had caught up with losses and were increasing their fleet. The Allies were also intercepting German U-boat communications through the Ultra programme which made a real difference. Then, in March 1943, Ultra failed for a short time during which the Germans sighted every single Allied convoy and attacked over half of them. But, finally, the Battle of the Atlantic was turning in the favour of the Allies. Once more able to break the German codes, using more modern radar equipment, with the addition of new aircraft carriers to the escort groups, and more aggressive tactics meant that, by May 1943, the success of the German U-boat fleet in the North Atlantic was severely diminished. For the remainder of the war the Allies had more or less unchallenged control of the Atlantic sea lanes.

The men and women who served with the Army, Royal Air Force and Royal Navy are frequently remembered for their courage, and rightly so. But the men of the merchant navy who sailed the gauntlet of an ocean of hidden submarines to re-supply ‘Fortress Britain’ are often forgotten. Yet their courage and sacrifice under fire was no less heroic, and without them the war might well have been lost.

Allied losses during the Battle of the Atlantic

36,200 sailors killed
36,000 merchant seamen killed
3,500 merchant vessels sunk
175 warships sunk
741 RAF Coastal Command Aircraft lost in anti-submarine sorties

Bibliography

The Battle of the Atlantic by Andrew Williams

Captain Gilbert Roberts RN and the Anti-U-boat School by Mark Williams

In Great Waters: The Epic Story of the Battle of the Atlantic by Spencer Dunmore

The Battle of the Atlantic by Macintyre, Donald.