U-boat campaign

U-boat campaign
Part of the naval theatre of World War I
A German postcard depicting the U-boat SM U-20 sinking RMS Lusitania
Date 28 July 1914 – 11 November 1918 (4 years, 3 months and 2 weeks) Location Atlantic Ocean, North Sea, Mediterranean Sea, Black Sea Result Allied victory
Belligerents
Royal Navy Royal Canadian Navy  French Navy  Regia Marina  United States Navy  Imperial Japanese Navy  Brazilian Navy  Imperial Russian Navy  Royal Romanian Navy	Imperial German Navy  Austro-Hungarian Navy  Bulgarian Navy
Commanders and leaders
Lord Fisher Sir Henry Jackson Sir John Jellicoe Sir Rosslyn Wemyss	Hugo von Pohl Gustav Bachmann Henning von Holtzendorff Reinhard Scheer
Strength
~500 Royal Navy destroyers[1] ~250 US destroyers[2] Various armed trawlers and smaller vessels Defensively armed merchant ships 366 Q-ships	351 U-boats
Casualties and losses
5,000 merchant ships sunk[3] 15,000 merchant sailors killed 104 warships sunk[4] 42 warships damaged 61 Q-ships sunk[5]	217 U-boats lost to all causes 6,000 sailors killed

The U-boat campaign from 1914 to 1918 was the World War I naval campaign fought by German U-boats against the trade routes of the Allies, largely in the seas around the British Isles and in the Mediterranean, as part of a mutual blockade between the German Empire and the United Kingdom.

Both Germany and Britain relied on food and fertilizer imports to feed their populations, and raw materials to supply their war industry. The British Royal Navy was superior in numbers and could operate on most of the world's oceans because of the British Empire, whereas the Imperial German Navy surface fleet was mainly restricted to the German Bight, and used commerce raiders and submarine warfare to operate elsewhere.

German U-boats sank almost 5,000 ships with over 12 million gross register tonnage, losing 178 boats and about 5,000 men in combat.^[6] U-boats operated in the Atlantic and the Mediterranean, and to a lesser degree in both the Far East and South East Asia, and the Indian Ocean. However, the Allies were able to keep a fairly constant tonnage of shipping available, due to a combination of ship construction and countermeasures, particularly the introduction of convoys.^[7]