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Unrestricted Warfare in the Atlantic - The U-boat threat - The First World War

U-boats had already shown their capabilities in the First World War, having caused outrage in the united States following the sinking of the Lusitania early in the war. Now, eager to bring the British people to their knees, the German High Command calculated that lifting all restrictions placed on their U-boat commanders would result in victory.

German submariners had, since the sinking of the Lusitania, been under orders to only engage warships. Unrestricted warfare quite simply meant that any vessel they came across was a legitimate target. This led to U-boats quickly wreaking havoc amongst the merchant navies of Britain, Canada and the United States. Shipping losses rocketed with over 500,000 tonnes of shipping lost in march, over 800,000 tonnes in April and 600,000 tonnes in May.

The results were crippling for the British. The lifting of restrictions on the U-boats meant shortages of food and essential supplies. The response of the Allied fleets was to create convoys. A large number of merchant ships would sail across the Atlantic together, with a naval escort to deter U-boats. Loss of ships still occurred, but the number of boats reaching their final destination rose steadily as the U-boats were detected quickly and forced to make a hasty exit from the scene.

Another result of the unrestricted attacks on shipping was the declaration of war on Germany by the United States government.

Read about other aspects of the War at Sea.