Editing Electrical telegraph (section)

===Second World War===
[[File:Lorenz SZ42.jpg|thumb|German Lorenz SZ42 teleprinter attachment (left) and Lorenz military teleprinter (right) at [[The National Museum of Computing]] on [[Bletchley Park]], England]]
[[World War II]] revived the 'cable war' of 1914–1918. In 1939, German-owned cables across the Atlantic were cut once again, and, in 1940, Italian cables to South America and Spain were cut in retaliation for Italian action against two of the five British cables linking Gibraltar and Malta. [[Electra House]], Cable & Wireless's head office and central cable station, was damaged by German bombing in 1941.

[[Resistance during World War II|Resistance movements]] in occupied Europe sabotaged communications facilities such as telegraph lines,<ref>{{Citation |title=World War II: German-occupied Europe |publisher=Encyclopaedia Britannica |url=https://www.britannica.com/event/World-War-II/German-occupied-Europe}}</ref> forcing the Germans to use [[wireless telegraphy]], which could then be [[Y-stations|intercepted]] by Britain.
The Germans developed a highly complex teleprinter attachment (German: ''Schlüssel-Zusatz'', "cipher attachment") that was used for enciphering telegrams, using the [[Lorenz cipher]], between German High Command ([[Oberkommando der Wehrmacht|OKW]]) and the army groups in the field. These contained situation reports, battle plans, and discussions of strategy and tactics. Britain intercepted these signals, diagnosed how the encrypting machine worked, and [[Cryptanalysis of the Lorenz cipher|decrypted]] a large amount of teleprinter traffic.{{sfn|Copeland|2006|pp=1–6}}