Also of great significance during World War I was the Russian failure to distribute "cryptosystems" to some army units in 1914. The messages that the Germans intercepted were thus uncoded. The Germans used them to encircle and destroy a Russian army at the Battle of Tannenberg (August 25–30). Although the Russians later enciphered their messages, the Germans easily solved them, greatly contributing to Germany's defeat of czarist Russia. Thus German signals intelligence helped deliver Russia to the Bolsheviks.
During World War II massive cryptanalysis of German military and naval cryptograms helped the Allies win that conflict. Solutions of German naval messages that were enciphered using the cipher machine Enigma revealed orders to and reports from U-boats at sea. This intelligence enabled convoys traveling from America to Britain to detour around the "wolf packs" (groups of submarines that made coordinated attacks on shipping). Later it permitted Allied warships to pinpoint the submarines in the vastness of the ocean and sink them.
In the land campaigns in North Africa and Europe, the breaking of German Air Force and Army messages enciphered in Enigma, among other systems, prepared the Allies to win many battles. In Normandy on Aug. 6, 1944, for example, a decoded message revealed that the Germans would soon launch a heavy attack from around Mortain with fighter plane protection. Owing in part to this warning, the U.S. 30th Infantry Division repelled the onslaught.
Likewise, American "codebreakers" significantly shortened World War II in the Pacific Ocean. The reading of coded Japanese naval messages told the Americans as much about some Japanese plans as the captains of Japanese naval vessels knew and enabled them to ambush the Japanese fleet at Midway Island in the central Pacific on June 4, 1942. The battle there turned the tide of the war in the Pacific. Other solutions facilitated American submarines' sinking of Japanese cargo ships, bringing the island empire to the verge of collapse.
While the solution of the chief Japanese diplomatic cipher machine, called PURPLE by the Americans, did not avert the surprise of Pearl Harbor -because no messages even hinting at the attack ever went to the diplomats- it contributed enormously to wartime intelligence through the reading of reports sent home by Japanese diplomats in Berlin. These revealed Adolf Hitler's thoughts and plans. The Soviet Union, too, broke this machine. Its solutions disclosed time and again that Japan was not planning to attack the USSR from the rear, thus easing Joseph Stalin's decision making.
The value of cryptanalysis during World War II was summarized in 1944 by U.S. Army chief of staff Gen. George C. Marshall: "The conduct of General Eisenhower's campaign [in Europe] and of all operations in the Pacific are closely related in conception and timing to the information we secretly obtain through these intercepted codes. They contribute greatly to the victory."
During the Korean and Vietnamese conflicts, U.S. signals intelligence was responsible for reducing American casualties. And at least once during Operation "Desert Storm" in 1991, intercepted Iraqi communications were sent to U.S. tanks in time to warn of Iraqi artillery that was about to target them, enabling them not only to take evasive action but also to counterattack. More generally, signals intelligence played a considerable part in the victory of the United States and its allies.
Communications intelligence also helps in peacetime. During the naval disarmament conference held in Washington in 1921 and 1922, American solution of Japanese diplomatic cablegrams helped U.S. diplomats to compel Japan to accept the equivalent of a battleship and a half less than it wanted. During the tense American-Japanese negotiations in the spring of 1995 over automobile imports, American interception of telephone conversations between the executives of Toyota and Nissan and Japan's trade minister told the United States trade representative and his staff how far the Japanese could be pressed and helped bring about an accord. By warning of possible hostile actions, cryptanalysts continue to give policymakers time to plan actions and thus figure importantly in stabilizing the international system.
