Signals intelligence in modern history

Before the development of radar and other electronics techniques, signals intelligence (SIGINT) and communications intelligence (COMINT) were essentially synonymous. Sir Francis Walsingham ran a postal interception bureau with some cryptanalytic capability during the reign of Elizabeth I, but the technology was only slightly less advanced than men with shotguns, during World War I, who jammed pigeon post communications and intercepted the messages carried. Flag signals were sometimes intercepted, and efforts to impede them made the occupation of the signaller one of the most dangerous on the battlefield. The middle 19th century rise of the telegraph allowed more scope for interception and spoofing of signals, as shown at Chancellorsville. Signals intelligence became far more central to military (and to some extent diplomatic) intelligence generally with the mechanization of armies, development of blitzkrieg tactics, use of submarine and commerce raiders warfare, and the development of practicable radio communications. Even measurement and signature intelligence (MASINT) preceded electronic intelligence (ELINT), with sound ranging techniques for artillery location. SIGINT is the analysis of intentional signals for both communications and non-communications (e.g., radar) systems, while MASINT is the analysis of unintentional information, including, but not limited to, the electromagnetic signals that are the main interest in SIGINT.

Origins

Electronic interception appeared as early as 1900, during the Boer Wars. The Royal Navy had installed wireless sets produced by Marconi on board their ships in the late 1890s and some limited wireless signalling was used by the British Army. Some wireless sets were captured by the Boers, and were used to make vital transmissions. Since the British were the only people transmitting at the time, no special interpretation of the signals was necessary. The Imperial Russian Navy also experimented with wireless communications under the guidance of Alexander Popov, who first installed a wireless set on a grounded battleship in 1900. The birth of signals intelligence in a modern sense dates to the Russo-Japanese War. As the Russian fleet prepared for conflict with Japan in 1904, the British ship HMS Diana stationed in the Suez canal was able to intercept Russian naval wireless signals being sent out for the mobilization of the fleet, for the first time in history. "An intelligence report on signals intercepted by HMS Diana at Suez shows that the rate of working was extremely slow by British standards, while the Royal Navy interpreters were particularly critical of the poor standard of grammar and spelling among the Russian operators". The Japanese also developed a wireless interception capability and succeeded in listening in to the then primitive Russian communications. Their successes emphasized the importance of this new source of military intelligence, and facilities for the exploitation of this information resource were established by all the major powers in the following years. The Austro-Hungarian Evidenzbureau was able to comprehensively monitor the progress of the Italian army during the Italo-Turkish War of 1911 by monitoring the signals that were sent by a series of relay stations from Tripoli to Rome. In France, Deuxième Bureau of the Military General Staff was tasked with radio interception.

World War I It was over the course of the War that the new method of intelligence collection - signals intelligence - reached maturity. The British in particular built up great expertise in the newly emerging field of signals intelligence and codebreaking. Failure to properly protect its communications fatally compromised the Russian Army in its advance early in World War I and led to their disastrous defeat by the Germans under Ludendorff and Hindenburg at the Battle of Tannenberg. France had significant signals intelligence in World War I. Commandant Cartier developed a system of wireless masts, including one on the Eiffel Tower to intercept German communications. The first such station was built as early as 1908, although was destroyed by flooding a few years afterward. In the early stages of the war, French intercepts were invaluable for military planning and provided the crucial intelligence to commander-in-chief Joseph Joffre that enabled him to carry out the successful counterattack against the Germans at the Marne in September 1914. In 1918, French intercept personnel captured a message written in the new ADFGVX cipher, which was cryptanalyzed by Georges Painvin. This gave the Allies advance warning of the German 1918 Spring Offensive. US communications monitoring of naval signals started in 1918, but was used first as an aid to naval and merchant navigation. In October 1918, just before the end of the war, the US Navy installed its first DF installation at its station at Bar Harbor, Maine, soon joined by five other Atlantic coast stations, and then a second group of 14 installations. These stations, after the end of World War I, were not used immediately for intelligence. While there were 52 Navy medium wave (MF) DF stations in 1924, most of them had deteriorated.

Cracking the German naval codes

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