During World War I, the most hazardous place to be, relatively speaking, was not on the battlefield, but inside a German U-boat.
![This map indicates the location of ships sunk by U-boat activity in the Mediterranean, the Atlantic, and the North Sea, specifically within those areas open to unrestricted warfare. The total was roughly 7,500 vessels. Die Schiffsversenkungen unserer U-Boote : nach Lage und Zahl dargestellt auf Grund amtlichen Materials mit Seeschlachten, Sperrgebieten, Landfronten, Land-Gewinn und -Verlust / redigiert von Prof. Dr. J.I. Kettler. (Berlin und Glogau: Carl Flemming AG, [1918]). Scale 1:7,500,000. LC call number G5701.S65 1918 .C2](http://blogs.loc.gov/maps/files/2019/10/default.jpg)
This map indicates the location of ships sunk by U-boat activity in the Mediterranean, the Atlantic, and the North Sea, specifically within those areas open to unrestricted warfare. The total was roughly 7,500 vessels. Die Schiffsversenkungen unserer U-Boote : nach Lage und Zahl dargestellt auf Grund amtlichen Materials mit Seeschlachten, Sperrgebieten, Landfronten, Land-Gewinn und -Verlust / redigiert von Prof. Dr. J.I. Kettler. (Berlin und Glogau: Carl Flemming AG, [1918]). Scale 1:7,500,000. LC call number G5701.S65 1918 .C2
By the beginning of 1917, Germany’s economy had become beleaguered by blockaded ports and its war effort threatened by American munitions shipments. In response, it resumed its policy of unrestricted submarine warfare on Allied merchant ships on February 1, 1917.
The renewed German practice proved successful, accounting for just over 3,700 vessels sunk, damaged, disabled, or captured in 1917 alone, and included ships of all types and sizes, from trawlers to military transports to luxury liners. Generally unable to dive more than fifty meters or remain submerged for more than two hours, U-boats sunk enemy ships by firing surface torpedoes or laying mines.
![U-Bootswirkung im Mittelmeer. / 12 Monate uneingeschrankten U-Bootskrieges auf dem Mittelmeer-Kriegsschauplatz. ([Berlin]: Gedruckt im Admiralstab der Marine, [1918]). Scale 1:5,400,000. Geography and Map Division. Europe – Mediterranean – War / World War I – 1917 – 1:5,400,000 – Adm. der. Marine](http://blogs.loc.gov/maps/files/2019/10/Untitled.jpg)
U-Bootswirkung im Mittelmeer. / 12 Monate uneingeschrankten U-Bootskrieges auf dem Mittelmeer-Kriegsschauplatz. ([Berlin]: Gedruckt im Admiralstab der Marine, [1918]). Scale 1:5,400,000. Geography and Map Division. Europe – Mediterranean – War / World War I – 1917 – 1:5,400,000 – Adm. der. Marine
Sailing out of an Austro-Hungarian naval base, such as the one at Kotor in modern-day Montenegro, the twenty-three-or-so U-boats assigned to the Mediterranean terrorized the region and the Luso-Hispanic coast. Who were the likely victims of unrestricted submarine warfare in those areas? Among them could have been Greek and Italian fishing boats, a Portuguese anchovy trawler, a Spanish yacht, a North African dhow, an American munitions transport, a French cruiser, or a British hospital ship.
![The frightfulness of German submarine warfare, especially its toll on non-combatants, is illustrated in a wartime editorial cartoon. [Toll of German subs sinking ships in Mediterranean]. Lute Pease. [between 1914 and 1918]. Drawing. Print and Photographs Division.](http://blogs.loc.gov/maps/files/2019/10/2a10828r.jpg)
The frightfulness of German submarine warfare, especially its toll on non-combatants, is illustrated in a wartime editorial cartoon. [Toll of German subs sinking ships in Mediterranean]. Lute Pease. [between 1914 and 1918]. Drawing. Print and Photographs Division.
![The map indicates areas prowled by U-boats during the war. It also includes cross-sections of nine segments of vessels in the U-139 and U141 classes, in addition to exposed views of their sides and four decks, and an index of their features. Sperrgebiete um Europa und Afrika / Geograph. Anstalt von Wagner & Debes in Leipzig. (Leipzig: Verlag von K.F. Koehler, [1925]). Scale ca. 1:24,000,000. Geography and Map Division. LC call number G5701.S65 1925 .W2](http://blogs.loc.gov/maps/files/2019/10/selection.jpg)
The map indicates areas prowled by U-boats during the war. It also includes cross-sections of nine segments of vessels in the U-139 and U141 classes, in addition to exposed views of their sides and four decks, as well as an index of their features. Sperrgebiete um Europa und Afrika / Geograph. Anstalt von Wagner & Debes in Leipzig. (Leipzig: Verlag von K.F. Koehler, [1925]). Scale ca. 1:24,000,000. Geography and Map Division. LC call number G5701.S65 1925 .W2
One Internet-based resource with much helpful information on WWI U-boats, including a list of all U-boats commissioned before the end of the War, is uboat.net https://uboat.net/wwi/.