Armies in the First World War were vast compared with armies in preceding wars. The telephone, telegraph and the appearance of effective wireless radio sets were replacing older communication methods. The article in Scientific American from March 17, 1917, says:
“With an army strung out over miles of irregular trenches prompt communication by the older method is obviously impossible, although special instructions carried by fast motorcycles have been found greatly superior to the old horse-mounted messengers; but where rapid communication with the commanders of long lines of trenches, and numerous widely scattered batteries of guns, is necessary something vastly more prompt and certain is required, and in this emergency recourse is had to the telephone, which has proved to be indispensable. By means of telephones, operated through heavily insulated wires that can be run rapidly from point to point, resting directly upon the ground without any supports or elaborate fixtures, orders may be transmitted along miles of trenches within a few minutes, where flags could not be seen, and where messengers even on the fastest motorcycles would require hours, even if they got through safely at all, thus enabling rapid cooperative action to be taken, or special advances organized and properly supported both by troops and guns.”
Artillery, though, frequently cut telephone wires, so “runners” carrying messages back and forth were widely used. As warfare became more mobile late in the war, static telephone lines became less useful, while radios were becoming more portable. (Carrier pigeons, it should be noted, remained useful until well after the Second World War.)
The views expressed are those of the author and are not necessarily those of Scientific American.
Our full archive of the war, called Scientific American Chronicles: World War I, has many articles from 1914–1918 on communication during the First World War. It is available for purchase at www.scientificamerican.com/products/world-war-i/