Battles & Wars › Revolutions & Napoleon
Electric telegraph and Morse code
1837 (Cooke–Wheatstone; Morse); Morse's line 1844· Invention or discovery· Technology, codes & intelligence
Well documentedSolid records, physical evidence or scientific consensus.
Sending messages as electric pulses over wire, in Morse's dot-and-dash code, made distant communication nearly instant.
See it on the Battles & Wars map →What happened
In 1837 William Cooke and Charles Wheatstone patented a needle telegraph in Britain, first used along a railway. In the US, Samuel Morse, a painter, and Alfred Vail built a simpler system and a code of dots and dashes. Congress funded a Washington–Baltimore line; on May 24, 1844 it carried 'What hath God wrought.' Wires followed railways across continents, and a lasting transatlantic cable worked from 1866. Messages that had taken weeks now took minutes.
Why it matters
Governments could direct distant armies, newspapers could report wars within a day, and empires ran on cable. It began electrical communication, leading to radio and today's networks.
How we know
Patents, surviving instruments, the paper tape of Morse's 1844 message at the Library of Congress, and telegraph company and military records.
Still debated
Credit is disputed: Joseph Henry's electromagnet work and German and Russian experimenters of the early 1830s came first with parts of the idea.
Inside this (2)
Connections (6)
▸Optical telegraph (Chappe semaphore) was replaced by the Electric telegraph and Morse codeWell documented
The connection
The electric telegraph worked at night and in fog, far faster and with fewer operators. France, which had the largest optical network, was slow to switch, but from the mid-1840s electric lines replaced the towers, and the last Chappe lines closed in the 1850s. Most towers were abandoned; a few survive restored.
When and how
France, Britain and elsewhere, 1840s–1850s; France's first electric telegraphs, from 1845, even displayed the old Chappe arm positions.
How we know
Government decisions and network records document the changeover in detail.
Debates and open questions
Why France kept its optical system so long, partly to keep state control of messages, is debated.
▸Electric telegraph and Morse code first linked generals to home capitals in the Crimean WarMostly agreed
The connection
In 1855 British engineers laid an undersea cable across the Black Sea from Varna, in today's Bulgaria, to the Crimea, joining Europe's networks. London and Paris could now message their commanders in under a day instead of weeks. Generals found themselves second-guessed: Napoleon III's telegraphed instructions contributed to the French commander Canrobert's resignation.
When and how
Black Sea and Crimea, April 1855; British and French commanders before Sevastopol, linked to London and Paris.
How sure are we?
Telegraph company and government records, and commanders' complaints in their letters, document the link; its exact effect on decisions is less clear.
Debates and open questions
Whether faster contact improved strategy or mostly caused meddling is debated; the American Civil War, a few years later, used telegraphs far more widely.
▸Electric telegraph and Morse code let Lincoln follow battles in the American Civil WarWell documented
The connection
The Union's U.S. Military Telegraph strung about 15,000 miles of line and handled millions of messages. Lincoln spent long hours in the War Department telegraph office, reading reports from the front and wiring generals directly, sometimes within hours of a battle. Field crews ran wires to headquarters, and both sides tapped each other's lines.
When and how
Washington and the war's fronts, 1861–65; Lincoln, Secretary of War Edwin Stanton, and telegraph chiefs such as Anson Stager and Thomas Eckert.
How we know
Lincoln's surviving telegrams, the telegraph office's records, and operators' memoirs, such as David Homer Bates's 'Lincoln in the Telegraph Office' (1907).
Debates and open questions
Historians debate whether Lincoln's close monitoring helped by prodding slow generals or hurt by encouraging political meddling in operations.
▸Electric telegraph and Morse code was one of the three pillars of Railways, rifled muskets and the telegraphWell documented
The connection
Railways and the telegraph grew up together: wires ran beside tracks, and dispatchers used them to schedule trains on single-track lines. In war the pairing let commanders order troops forward and know where they were. Together with rifled muskets it changed war in the 1850s–60s, and Prussia's Moltke used it to win in 1866 and 1870.
When and how
US, Britain and Prussia, 1840s–1870; the Union's military railroads and telegraph, and Moltke's Prussian general staff.
How we know
Railway and military records show telegraph dispatching of troop trains; the pairing is standard in histories of 19th-century war.
Debates and open questions
How far this industrial trio changed outcomes, compared with numbers and leadership, is debated among military historians.
▸Electric telegraph and Morse code went wireless as Radio (wireless telegraphy)Well documented
The connection
Wires carried Morse code across continents from the 1840s but could not reach ships at sea or fast-moving armies. Marconi's radio sent the same dots and dashes through the air on electromagnetic waves. Navies were the first big buyers; Britain's Royal Navy ordered Marconi sets in 1900, and soon fleets could be commanded beyond sight of land.
When and how
Bologna, Italy, 1895; Britain, 1896–97 (patent and demonstrations); first transatlantic signal, December 12, 1901; Royal Navy orders from 1900.
How we know
Marconi's patents and demonstration records, navy contracts, and the use of Morse code over radio by ships until the 1990s.
Debates and open questions
How much Marconi invented, rather than combining others' discoveries such as Hertz's waves and Édouard Branly's detector, is still argued.
▸Electric telegraph and Morse code carried, by undersea cable, the Zimmermann Telegram (broken by Room 40)Well documented
The connection
In August 1914 Britain cut Germany's undersea cables, so Germany had to send overseas messages through other countries' lines. The Zimmermann message went by the American diplomatic cable, which President Wilson had let Germany use for peace talks, and by a Swedish route. Both passed through Britain, where Room 40 copied and decrypted it.
When and how
English Channel, August 1914 (cable ship Alert); Berlin and London, January 16–17, 1917; Room 40 codebreakers Nigel de Grey and William Montgomery, under Admiral William Hall.
How we know
British Admiralty files and the decrypt itself, now in the UK National Archives, and US State Department records of the diplomatic cable.
Debates and open questions
Which route Room 40 first read the message from was long kept secret, and historians still disagree on the details.