Shortly after the invention of the telephone attempts were made to adapt the technology for military use. Telephones were already being used to support military campaigns in British India and in British colonies in Africa in the late 1870s and early 1880s. In the United States telephone lines connected fortresses with each other and with army headquarters. They were also used for fire control at fixed coastal defence installations. The first telephone for use in the field was developed in the United States in 1889 but it was too expensive for mass production. Subsequent developments in several countries made the field telephone more practicable. The wire material was changed from iron to copper, devices for laying wire in the field were developed and systems with both battery-operated sets for command posts and hand generator sets for use in the field were developed. The first purposely-designed field telephones were used by the British in the Second Boer War.Sterling, Christopher H.; Military Communications: From Ancient Times to the 21st Century (2008). Santa Barbara: ABC-CLIO. p. 444. They were used more extensively in the Russo-Japanese War, where all infantry regiments and artillery divisions on both sides were equipped with telephone sets.Ivanov, Alexei and Philipp S. Jowett; The Russo-Japanese War 1904-1905 (2004). Oxford: Osprey Publishing. p. 11. By the First World War the use of field telephones was widespread.Sterling p. 445.
Field telephones operate over telephone line, sometimes commandeering civilian circuits when available, but often using wires strung in combat conditions. An account of line stringing in WW II At least as of World War II, wire communications were the preferred method for the U.S. Army, with radio use only when needed, e.g. to communicate with mobile units, or until wires could be set up. Field phones could operate point to point or via a switchboard at a command post. Signal Operations in the Corps and Army, FM 11-22, U.S. War Department, January 1945 A variety of wire types are used, ranging from light weight "assault wire," e.g. W-130 —— with a talking range about , to heavier cable with multiple pairs. Equipment for laying the wire ranges from reels on backpacks to trucks equipped with plows to bury lines. Wire and Cable Equipment, World War II
Torture of POWs
According to the Army's Vietnam War Crimes Working Group Files, field telephones were sometimes used in Vietnam to torture POWs with electric shocks during .
Field telephones of the Soviet Union
Field telephones used by the Royal Norwegian Defence Forces
Field telephones used by the Finnish Defence Forces