Seventy years ago this day the first Arctic Convoy set off from Scotland en route to Murmansk in Northern Russia. Between August 1941 and May 1945, 78 convoys comprising some 1400 merchant ships completed what Winston Churchill called, “the worst journey in the world” to deliver vital war supplies to Soviet Russia under a lend-lease agreement with the United Kingdom and United States.

The convoys were escorted by the ships of the Royal Navy, supported by units of the Royal Canadian and US navies. Over that period 85 merchant ships were sunk by enemy action, together with 2 Royal Navy cruisers, 6 destroyers and 8 other escort ships. Sinking was almost certainly fatal as life expectancy in the freezing waters of the Norwegian Sea and the Arctic Ocean amounted to a few minutes at best.

Operating under constant threat of air and U-boat attack from occupied Norway the convoys had to operate either in perpetual dark or perpetual light. Moreover, severe weather, fog, strong currents and the mixing of warm and cold waters not only made the use of ASDIC (sonar) difficult, but also greatly complicated convoy cohesion.

Keeping ships together was vital. In July 1942 convoy PQ17 suffered the worst losses of any convoy in World War Two. Fatally, following constant attacks by air and the threat from the German fast battleship Tirpitz (sister ship of the Bismarck), the convoy was ordered to scatter. Only 11 out of 35 ships made it to Archangelsk on Russia’s Arctic coast.

Hitler deemed the convoys to be of such strategic importance that intense efforts were made by the Luftwaffe and the Kriegsmarine to disrupt them, but at an enormous cost to both services. On December 26, 1943 Admiral Sir Bruce Fraser, flying his flag in the battleship HMS Duke of York and supported by the cruisers HMS Belfast, HMS Jamaica, HMS Norfolk and HMS Sheffield, trapped and sank the German battle-cruiser Scharnhorst by employing for the first time radar-controlled gunnery. In the Arctic twilight Duke of York straddled Scharnhorst with the first salvo from her 14 inch guns. On 12 November 1944 32 Royal Air Force Lancasters from Nos 9 and 617 (Dambusters) squadrons dropped the massive Tallboy bombs on the Tirpitz as she sat in Norway’s Tromso Fjord. She rolled over and sank within minutes. In all the Germans lost 2 battleships, 3 destroyers and some 30 U-boats in addition to many aircraft.

The convoys provided essential support to a hard-pressed Soviet Union, particularly during the siege of Leningrad in 1941 and 1942 by delivering critical food and ammunition supplies. As the war moved towards its conclusion the Soviets insisted the convoys continue, mainly for symbolic reasons. In the end the Arctic Convoys proved a decisive victory for the Allies, but at an enormous cost in lives and ships.

Vital to that success was ULTRA intelligence gained as a result of the cracking of the German Enigma code at Bletchley Park in southern England. This enabled the Royal Navy not only to make the best use of its forces, but also provided the forewarning to route convoys around U-boat wolf packs and German surface raiders.

Seventy years on from what was an epic struggle which claimed the lives of thousands of men on both sides it is right that we pause and remember their sacrifice.

Professor Julian Lindley-French, a member of the Atlantic Council Strategic Advisor’s Group, is Special Professor of Strategic Studies, University of Leiden, Netherlands and Associate Fellow of the Royal Institute of International Affairs, London. This essay first appeared on his personal blog, Lindley-French’s Blog Blast. Photo credit: RBTH.