Within hours of Britain's entry into the Second World War on 3 September 1939, the first engagement had taken place in a battle that would rage for the next six years and cost tens of thousands of lives. A German U-boat commander mistaking the passenger liner SS Athenia for an armed merchant vessel attacked and sank the ship with the loss of more than 100 lives.


Great Britain was a maritime power and relied on the sea for trade and imports of food, equipment and raw materials. The Royal Navy protected its overseas interests and the merchant ships that transported these crucial supplies. During the Second World War, the struggle between the Allies and German submarines - Unterseebootsor boats (U-boats) - became known as the Battle of the Atlantic and was vital to the outcome of the war.

Happy Time

By the summer of 1940, U-boats could operate from bases in occupied Europe which greatly extended their range. With the reintroduction of the convoy system for Allied merchant vessels, the Royal Navy had to provide escorts for increasingly long stretches of their journey. This was a task that began to seriously test the Navy’s resources of ships and manpower.

The U-boat’s effectiveness was enhanced further by the German air force’s use of bases in France and Norway. Long range reconnaissance aircraft could now locate convoys and direct the U-boats to them leading to the development of the 'wolf pack' tactic, whereby a number of U-boats would gather and co-ordinate their attack against a convoy.

The wolf packs would usually attack at night and on the surface, overwhelming the escort ships and largely nullifying the one weapon the escorts had to detect submarines underwater – ASDIC, an early form of sonar. By the end of 1940, hundreds of thousands of tons of Allied shipping had been sunk. The success was referred to by the U-boat crews as ‘The Happy Time.’

During this period, British industry was struggling to replace the lost tonnage, while supplies of basic foods and vital raw materials dwindled significantly. Many goods were severely rationed and would continue to be so throughout the war. In human terms, the men of the Merchant Navy were suffering terrible losses and experienced crews were hard to replace.

Fighting Back

The Royal Navy had to adapt quickly. Improved training for escort crews, better tactics, undersea detection equipment and weapons, including new escort vessels like the corvette, all helped to reduce Allied losses while inflicting heavier punishment on the U-boats. Assistance from the Royal Canadian Navy and the US Navy also helped to reduce the burden. The capture of a German 'Enigma' machine by the crew of HMS Bulldog in May 1941 helped cryptographers to break the German naval codes.

However, one major problem remained for the convoys: the mid-Atlantic Gap. This was a vast area of ocean that could not be reached by Allied aircraft and within which the U-boats could operate at will. The mid-Atlantic Gap was finally closed by using special aircraft carriers in conjunction with new long-rang aircraft, which became available to the Allies in the second half of 1943. They were immediately effective in countering German reconnaissance aircraft, sinking or damaging many U-boats and forcing others to remain submerged.

Turning Point

Despite the many innovations employed by the Allies, U-boats continued to inflict heavy losses on Allied shipping. The U-boats had a second 'Happy Time' just after the US joined the war in December 1941. Initially, the Americans were slow to learn from the experiences of the Commonwealth seamen and in the first few months of 1942 some 200 ships, mostly petrol tankers, were sunk off the United States’ east coast. In June the U-boats sank more than 830,000 tons of shipping, the worst month of the war for the Allies, but in July American industrial might began to have a significant effect on the battle. July 1942 was the first month of the war that replacement shipping began to exceed losses.

The turning point of the Battle of the Atlantic came in May 1943. By this time there were some 200 operational U-boats but, with US production reaching its peak, even this formidable force could not sink enough ships to prevent supplies getting through. Victory for the Allies in the industrial battle coincided with unprecedented success against the U-boats. The new tactics, intelligence, weapons and aircraft meant that in both April and May of 1943 the Germans lost 45 U-boats. More than the loss of the vessels, U-boat crews were hard to train and replace, while the effect on morale was devastating.

On 23 May 1943, the U-boats were called off by the German Naval Command. The battle did not end, but the threat had been greatly diminished. Victory in the Battle of the Atlantic paved the way for the invasion of mainland Europe in 1944 and the ultimate Allied victory.


At the end of the Second World War, Prime Minister Winston Churchill wrote that ‘The only thing that ever really frightened me during the war was the U-boat peril'. In human terms, the Battle of the Atlantic was a cruel and costly campaign that claimed a very high number of casualties on both sides. An estimated 80,000 Allied seamen were lost, while some 28,000 out of 41,000 U-boat crew perished.

related Cemeteries & Memorials

Portsmouth, Plymouth and Chatham naval memorials bear the names of those members of the Royal Navy who have no known grave.

In addition, there are memorials at Lowestoft and Liverpool for members of the Royal Naval Patrol Service and members of the Merchant Navy who died as a result of enemy action while serving with the Royal Navy. The Tower Hill Memorial in London commemorates those members of the Merchant Navy and Fishing Fleets who died as a result of enemy action.

Halifax Memorial, Canada, commemorates the men and women of the Royal Canadian Navy, the Royal Canadian Naval Reserve, the Canadian Merchant Navy and merchant seamen from Newfoundland who died during the Second World War and have no grave but the sea.

Members of the Fleet Air Arm are commemorated on their own memorial at Lee-on-the-Solent and the names of airmen serving with Royal Air Force Coastal Command will be found on the panels of the Air Forces at Runnymede Memorial.