The Battle of the Atlantic was the longest running campaign of the Second World War. It lasted the full duration of the war in Europe, from 3rd September 1939 until 8th May 1945. The Battle saw the Kriegsmarine U-Boats attempting to sink Allied shipping. With Britain reliant on supplies from overseas, the outcome of the war in Western Europe was reliant upon the Allies managing to overcome the threat posed by the U-Boat fleet. This was done through use of convoys and technological breakthroughs that enabled ASDIC (sonar) and long range air patrols of convoy routes.
Origins of the Battle of the Atlantic
As the Second World War began U-Boats were sent into the North Sea from ports in Germany. This submarine fleet was tasked with attacking the Royal Navy and Merchant Shipping bound for Great Britain. As early as 3rd September 1939 a Liner, the Athenia, was sunk by U-30 off the coast of Ireland. Fearing that unrestricted U-Boat attacks had begun, the British instigated the convoy system. However the sinking of the Athenia had been due to incorrect identification by the U-Boat, for months very little damage was done to shipping due to Hitler’s orders to adhere to International Law on shipping.
The first seven months of the war saw 319 ships sunk by U-Boats in and around British waters. Most of the attacks were in coastal waters or the western approaches. This included ships lost due to striking mines, attack from the air and the neutral vessels that sailed alone. The losses accounted for 883,000 gross tonnage of ships being lost.
… the only thing that ever really frightened me during the war was the U-boat peril. (Winston Churchill)
U-Boat tactics change
As the Wehrmacht launched Blitzkrieg on France and the Low Countries, U-Boat attacks increased. With the capture of ports the U-Boats were able to patrol further. They had additional targets as the fighting led to increased shipping to Great Britain. As troops were evacuated from France, U-Boats and Torpedo boats were able to pick off targets.
Though the number of U-Boats had not increased by June 1940, they were sinking many Allied ships. The tactic was to attack at night from the surface. As so many of the Allied ships were held in British waters in case of an invasion, the convoys were lightly guarded. A wolf pack could approach a convoy, then at night surface to attack. An attack from the surface was likely to be more accurate. The U-Boat was faster on the surface than it is submerged so was able to escape easily. June to December 1940 became known as the “Happy Time” for the U-Boat fleet.
Combatting the U Boat threat in the Atlantic
U Boats caused the most damage when they were able to attack isolated ships, or scatter a convoy. Panic was a weapon that they could use quite effectively. To minimise the risks to shipping the Allies needed to reduce the risk of shipping being isolated and make it easier to counter attack the U Boats. While a U Boat on the surface was faster than the escort ships, they had their weaknesses. U Boats could submerge to evade gunfire. If the location could be identified, they could be attacked underwater, using depth charges. They were unable to submerge to great depths. This meant that even submerged they could possibly be seen from the air. If air cover was possible, the threat was greatly reduced. Of course knowing where the U Boats were would reduce the risk. If the locations of the wolf packs could be established, then convoys could be routed in a way that minimised the risk. This was possible through breaking codes used by U Boat radios, though had to be carefully used so that the Kriegsmarine did not realise that their code was broken.
Improving the Atlantic Convoys
First and foremost the convoys needed to be well protected. The “Happy Time” had happened when many Royal Navy vessels were earmarked for other duties. Convoys had been escorted by fewer vessels than desirable and not always the best ones that the fleet had to offer. As the war progressed more ships were constructed. A Lend Lease agreement was made with the United States that brought additional ships into the Royal Navy. After the US Declaration of War, Liberty Ships were being constructed. These were built using new techniques which improved shipbuilding time from weeks to days.
ASDIC was developed. This was a form of sonar. This sent sound waves underwater that bounced back to the listener. Distances could be gauged using this technique. In the mid Atlantic the only thing that Sonar would pick up was a U Boat or Iceberg. This made it easier to identify where the U Boats were which meant Depth Charges could be deployed to sink them or force them to the surface.
Aircraft Carriers were brought into the Convoy system. With the ability to have patrols over the mid Atlantic the air coverage was much improved. U Boats could be attacked from the air, by bombardment from Destroyers or simply avoided.
Iceland. Iceland is strategically important. It provides the opportunity for land based aircraft to patrol the seas and for smaller, faster, vessels to be launched into the Northern parts of the Atlantic. This means it has the potential to control a large part of the convoy route from Newfoundland to Great Britain. To take advantage of this, the British simply seized the island and asked permission of the Danish rulers later.
Depth Charges. Depth charges were bombs designed to detonate underwater. They exploded at preset depths. They were fired from the sides and rear of ships. They were effective if they exploded near a U Boat but had limitations. Tracking the U Boat was important whilst an attack was underway. Using depth charges had limitations on this as attacking from the side and back reduced the ability to use ASDIC. During the course of the Battle of the Atlantic new forms of depth charge were introduced. These were forward facing that used mortar type technology to fire the charges. These were called Hedgehog (single charge) and Squid (triple charge).
Battle of the Atlantic: Surface Fleet Engagements
The main threat to the convoy system from the German surface fleet came from the large battleship the Bismarck. This was the largest Battleship that the Kriegsmarine put to sea in the Battle of the Atlantic. Bismarck made just one voyage. With orders to break out from German waters into the North Sea then Atlantic, she was intercepted the Royal Navy. The damage to the Bismarck incapacitated her as a fighting vessel and her crew scuttled her in May 1940. Her sister ship, the Tirpitz, along with the Scharnhorst, both posed a threat. These ships did dock in France for a time but due to the risk of being bombed by Allied planes were transferred to Norway. From here they attacked Allied shipping to the Soviet Union. The RAF sank Tirpitz in 1944. Scharnhorst was sunk by the Royal Navy at the Battle of North Cape in 1943.
Links
Naval History – detailed account of the Battle of the Atlantic. Provides a summary of the losses in each month of the campaign.
Imperial War Museum – pages on ‘What you need to know about the Battle of the Atlantic’
Sinking of RMS Lancastria – related material. The Lancastria was sunk off St. Nazaire while evacuating soldiers from France in June 1940.
Operation Outbreak – related material. The British Eastern Fleet operated from the Kenyan Coast. As the Allies began to take a firmer control of the Atlantic extra ships were sent there allowing the formation of the British Pacific Fleet. This Fleet attacked Sumatra on it’s way to joining the US Pacific Fleet for the Battle of Okinawa.
