Signals Intelligence in Modern History - World War I

World War I

Radio communications were fairly new at this time. At the strategic level, nations gained access to commercial undersea communication cable traffic. Tactically, wired telephones were in wide use, and techniques of intercepting them through ground returns were developed. These intercept techniques have had a resurgence in later wars, where radio was less available or impractical. On the declaration of war, one of Britain's first acts was to cut German undersea cables, forcing them to use radio, which the British could intercept. The destruction of more secure wired communications, to improve the intelligence take, has been a regular practice since then. While one side may be able to jam the other's radio communications, the intelligence value of poorly secured radio may be so high that there is a deliberate decision not to interfere with enemy transmissions.

Russia, when preparing for the Russo-Japanese War in 1904, had established a tradition of poor communications that would last well after the fall of the Romanovs. The success of this and related salvage and rescue work persuaded the Russian Navy to install wireless sets on many of its ships. In early 1904, the Russian fleet prepared for war with Japan. The British almost immediately began to intercept their communications, with the complaint “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.” After such an embarrassing start, the great Russian mathematical tradition, and probably the national passion for chess, has made Russia, regardless of other shortages, a great innovator in communications and cryptology.

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. Similarly, the interception and decryption of the Zimmerman telegram was an important factor in the US decision to enter the War.

Radio researchers at the British Marconi Company realized that strange signals they were receiving were German naval communications, and brought them to the Admiralty. Soon, the British were operating a network of listening posts called "Y-stations", with Admiralty Room 40 doing the traffic analysis and cryptanalysis. In World War II, the British referred to their traffic analysis function as the "Y service".

In contrast, battles have been lost, or not fought, when senior commanders asked the traffic analysts and direction finders the wrong question. In World War I, someone at the admiralty knew a little too much detail about SIGINT without fully understanding it. He asked the analysts where call sign "DK" was located, which was that used by the German commander when in harbour. The analysts answered his question precisely, telling him that it was "in the Jade River". Unfortunately the High Seas Fleet commander used a different identifier when at sea, going so far as to transfer the same wireless operator ashore so the messages from the harbour would sound the same. The misinformation was passed to Jellicoe commanding the British fleet, who acted accordingly and proceeded at a slower speed to preserve fuel. The battle of Jutland was eventually fought but its lateness in the day allowed the enemy to escape.

Jellicoe's faith in cryptographic intelligence was also shaken by a decrypted report that placed the German cruiser SMS Regensburg near him, during the Battle of Jutland. It turned out that the navigator on the Ravensburg was off by 10 miles (16 km) in his position calculation. During Jutland, there was limited use of direction finding on fleet vessels, but most information came from shore stations. A whole string of messages were intercepted during the night indicating with high reliability how the German fleet intended to make good its escape, but the brief summary which was passed to Jellicoe failed to convince him of its accuracy in light of the other failures during the day.

France had significant signals intelligence in World War I. While the key intelligence achievement in blunting the German drive on Paris in June 1918 was the cryptanalysis of Georges Painvin, had French intercept personnel not captured the message in the ADFGVX cipher, there would have been nothing to cryptanalyze.