Unrestricted submarine warfare
Unrestricted submarine warfare is a type of naval warfare in which submarines sink merchant ships such as freighters and tankers without warning. The use of unrestricted submarine warfare has had significant impacts on international relations in regards to both the First World War and the Second World War. Its history has been dominated by German decision making.
German U-boat U-14 (early 1910s)
German art of the sinking of the Linda Blanche on 30 January 1915 by SM U-21. Passengers and crew are being allowed to disembark into lifeboats, as per cruiser rules.
American cartoon by Oscar Cesare showing the sinking of the Lusitania. Sinkings of passenger vessels without warning incensed neutral opinion.
A submarine is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely operated vehicles and robots, as well as medium-sized or smaller vessels, such as the midget submarine and the wet sub. Submarines are referred to as boats rather than ships irrespective of their size.
US Virginia-class submarine underway in Groton, Connecticut, July 2004
Russian Akula-class submarine of the Northern Fleet, in 2008
An early submersible craft, built by Cornelis Drebbel, propelled by oars
1806 illustration by Robert Fulton showing a "plunging boat"