Devastation Wrought by U-Boats in WWI

Germany's use of unrestricted submarine warfare, where U-boat submarines were used to sink both military and merchant ships without warning, was very controversial and provocative. Smithsonian Magazine and GIS-mapping company Esri have created an interactive map of the attacks by German U-boats during WWI. The accompanying article by Li Zhou details Germany's decision to use this type of warfare and how it forever changed the rules of war.