Technological advances had made possible submarines armed with self-propelled torpedoes. In 1914, the British Royal Navy was the largest in the world, with 73 submarines; Germany had 31. The SM U 16 was a German Type 16 submarine. Submarines were given the designation “U” for Unterseeboot (submarine).

Osborne, Eric W. “Naval Warfare.” In 1914–1918–online. International Encyclopedia of the First World War, edited by Ute Daniel, Peter Gatrell, Oliver Janz, Heather Jones, Jennifer Keene, Alan Kramer, and Bill Nasson. Freie Universität Berlin, 2014–. Article published October 8, 2014. https://encyclopedia.1914-1918-online.net/article/naval_warfare.

Early in the war, Germany pursued a combined arms strategy of complementing unrestricted submarine warfare, aimed at interdicting maritime supplies and retaliating against the British naval blockade, with strategic aerial bombing carried out by Zeppelins, eventually “bombing London and introducing total war against civilians.” Zeppelins, named after their German inventor Ferdinand Zeppelin (1838–1917), were long-range airships with a metal frame. Germany was the first country to use them as a strategic weapon; they carried machine guns and high explosive and incendiary bombs. Zeppelins were given the designation “LZ” for Luftschiff Zeppelin (Airship Zeppelin).

Dusch, Charles: “Zeppelin (Airship).” In 1914–1918–online. International Encyclopedia of the First World War, edited by Ute Daniel, Peter Gatrell, Oliver Janz, Heather Jones, Jennifer Keene, Alan Kramer, and Bill Nasson. Freie Universität Berlin, 2014–. Article published January 25, 2019. https://encyclopedia.1914-1918-online.net/article/zeppelin_airship.

“Zeppelin, Ferdinand, Count von.” In World Encyclopedia. Philip’s, 2014. https://www.oxfordreference.com/view/10.1093/acref/9780199546091.001.0001/acref-9780199546091-e-12829.

The HMS Cressy, HMS Hogue, and HMS Aboukir were old and slow armoured British cruisers patrolling a stretch of the North Sea along the Dutch coast on the morning of September 22, 1914, when all three were sunk in just over an hour by a single German submarine, U 9, under the command of Otto Weddigen (1882–1915). The cruisers were named after British military victories against the French. The Battle of Crécy (1346) was the first major English victory on land in the Hundred Years War (1337-1453). The Battle of La Hogue (1692) restored English control of the Channel, and in the naval battle off Aboukir Bay (1798), the British defeated the French fleet.

Massie, Robert K. Castles of Steel: Britain, Germany, and the Winning of the Great War at Sea. New York: Ballantine Books, 2003, 128–39.

Jones, Mark. “Weddigen, Otto Eduard.” In 1914–1918–online. International Encyclopedia of the First World War, edited by Ute Daniel, Peter Gatrell, Oliver Janz, Heather Jones, Jennifer Keene, Alan Kramer, and Bill Nasson. Freie Universität Berlin, 2014–. Article published June 9, 2016. https://encyclopedia.1914-1918-online.net/article/weddigen_otto_eduard.