On this day in military history…
On the 3rd of September 1939, just hours after Britain declared war on Germany, the first British ship to fall victim to German naval aggression was the SS Athenia, a civilian passenger liner carrying over 1,100 people, including women and children. Torpedoed by German U-boat U-30 without warning, the attack shocked the world and signaled the beginning of a brutal and protracted naval campaign. Although the German High Command initially tried to deny involvement, the sinking of the Athenia made it clear that Germany’s U-boat fleet would once again be a deadly threat, echoing the devastation caused during the First World War. In response, the British Admiralty immediately began organizing its defenses. The very next day, on 4th September 1939, the long and grueling Battle of the Atlantic began.
The Battle of the Atlantic was not a single engagement but rather a continuous struggle for control over vital shipping routes between North America and Europe. Britain's survival depended on supplies brought by sea—food, fuel, raw materials, and military equipment. German U-boats, operating in coordinated "wolf packs," aimed to cut these lifelines, attempting to strangle Britain into submission through unrestricted submarine warfare. For the Royal Navy, as well as the Merchant Navy and later the Royal Canadian Navy and the United States Navy, the battle was a desperate effort to defend convoys against stealthy and lethal underwater predators.
In the early months of the war, the German U-boat fleet was relatively small, with fewer than 60 operational submarines. Nevertheless, they proved effective, operating mainly in the North Sea and around the British Isles. British countermeasures were initially limited. Convoy systems, which had been successful in World War I, were reinstated, but with insufficient escorts and outdated anti-submarine tactics, losses mounted quickly. The Germans, emboldened by their early success, expanded their operations into the Atlantic proper. They struck not only at military targets but also at neutral and civilian vessels, creating a climate of fear across the sea lanes.
As the war progressed into 1940 and 1941, the U-boat threat grew significantly. Following the fall of France in June 1940, German submarines gained access to Atlantic ports such as Lorient and Brest, allowing them to operate more freely and with greater range. U-boat commanders like Günther Prien and Otto Kretschmer became national heroes in Germany, racking up alarming tallies of ships sunk. British losses soared, especially during what became known as the "First Happy Time" for the U-boats. Ships were going down faster than they could be built, and for a time it seemed as though the balance of power might tip in Germany’s favor.
To counter the growing threat, Britain invested heavily in new technologies and tactics. The introduction of sonar, or ASDIC, allowed escorts to detect submerged submarines, although its effectiveness was limited in poor weather or rough seas. Depth charges became the primary weapon against submarines, though early on they were deployed more in hope than with precision. Escort carriers, long-range patrol aircraft, and improved coordination between Allied forces gradually started to make an impact. Code-breaking, particularly at Bletchley Park, where British cryptanalysts cracked the German Enigma cipher, proved crucial in giving the Allies advanced warning of U-boat positions and intentions.
By 1941, the United States, while not yet formally at war, began to support Allied convoys under the Lend-Lease program, and American warships took up escort duties in the Western Atlantic. After the Japanese attack on Pearl Harbor in December 1941 and Germany’s subsequent declaration of war on the United States, the Battle of the Atlantic entered a new phase. U-boats began attacking the American eastern seaboard in what they called the "Second Happy Time," taking advantage of poorly defended waters and unblackened coastal cities. Losses were catastrophic until the U.S. Navy implemented its own convoy system and improved its anti-submarine defenses.
From 1942 onwards, Allied efforts began to turn the tide. Better radar, high-frequency direction-finding equipment (known as "Huff-Duff"), and air cover from escort carriers and long-range bombers like the B-24 Liberator gradually closed the "air gap" in the mid-Atlantic where U-boats had previously operated with impunity. The development of the Hedgehog anti-submarine mortar allowed for more effective attacks on submerged submarines. In parallel, increased shipbuilding, particularly in American yards, began to outpace the rate of loss, ensuring that vital supplies could still reach Britain.
By mid-1943, the Battle of the Atlantic reached its turning point. In May of that year alone, Germany lost 41 U-boats, prompting Admiral Karl Dönitz, commander of the German submarine fleet, to temporarily withdraw many of his vessels. The Allies had gained the upper hand, and although U-boats continued to pose a threat until the end of the war, their ability to change the course of events had been blunted. German losses became unsustainable, both in men and material. By the time Germany surrendered in May 1945, more than 700 U-boats had been destroyed, and over 30,000 German submariners had lost their lives.
The Battle of the Atlantic was the longest continuous campaign of the Second World War, stretching from the very first days in September 1939 to the final surrender in 1945. It was a battle fought not only with ships and submarines, but with technology, intelligence, and endurance. The cost was enormous: over 3,500 Allied merchant ships and 175 warships were sunk, along with thousands of lives lost on both sides. Yet the victory in the Atlantic ensured that Britain could remain in the war, supplied and connected with her allies across the ocean. It was a victory that laid the foundation for the eventual liberation of Europe, proving that control of the seas remained as vital in the twentieth century as it had ever been before.
