Mediterranean and Middle East. At its core was the Allied naval blockade of Germany , announced the day after the declaration of war, and Germany's subsequent counter-blockade. The campaign peaked from mid to the end of Convoys , coming mainly from North America and predominantly going to the United Kingdom and the Soviet Union , were protected for the most part by the British and Canadian navies and air forces. These forces were aided by ships and aircraft of the United States beginning on 13 September As an island country, the United Kingdom was highly dependent on imported goods.
Britain required more than a million tons of imported material per week in order to survive and fight. The Battle of the Atlantic involved a tonnage war ; the Allied struggle to supply Britain, and the Axis attempt to stem the flow of merchant shipping that enabled Britain to keep fighting.
Rationing in the United Kingdom was also used with the aim of reducing demand, by reducing wastage and increasing domestic production and equality of distribution. From onwards, the Axis also sought to prevent the build-up of Allied supplies and equipment in the UK in preparation for the invasion of occupied Europe. The defeat of the U-boat threat was a prerequisite for pushing back the Axis in Western Europe. The outcome of the battle was a strategic victory for the Alliesβthe German tonnage war failedβbut at great cost: 3, merchant ships and warships were sunk in the Atlantic for the loss of U-boats and 47 German surface warships, including 4 battleships Bismarck , Scharnhorst , Gneisenau , and Tirpitz , 9 cruisers, 7 raiders, and 27 destroyers.
This front ended up being highly significant for the German war effort: Germany spent more money on producing naval vessels than it did every type of ground vehicle combined, including tanks. In addition, the Germans attributed GRTs sunk to ships with or without cargo aboard, to passenger and troop ships, and to warships.
Thus, measurements of GRT sunk each month had no relationship to shipments and was not limited to merchant freighters.
