The United States Coast Guard Unit 387 became the official cryptanalytic unit of the Coast Guard collecting communications intelligence for Coast Guard, U.S. Department of Defense, and the Federal Bureau of Investigation (FBI) in 1931. Prior to becoming official, the Unit worked under the U.S. Treasury Department intercepting communications during the prohibition. The Unit was briefly absorbed into the U.S. Navy in 1941 during World War II (WWII) before returning to be a Coast Guard unit again following the war. The Unit contributed to significant success in deciphering rum runner codes during the prohibition and later Axis agent codes during WWII, leading to the breaking of several code systems including the Green and Red Enigma machines.
The Rise of Unit 387 The U.S. Coast Guard (USCG) Unit 387 was established in the 1920s as a small embedded unit of the USCG. It did not become an officially named unit until 1931, when it was named the USCG Unit 387 by Elizebeth Friedman. The United States government established this code-communications unit to intercept ship communications and track down prohibition law breakers because “rum runners” were increasingly using radio and code systems for communication. There was an increasing need for code-breaking and encoding capabilities to counter the rum runners, as they were sophisticated criminals attempting to intercept government communications as well. By 1927, the USCG intercepted hundreds of messages but lacked the resources and personnel needed for codebreaking. Therefore, the U.S. Treasury Department appointed William and Elizebeth Friedman, a couple famous for cryptology, to create new code systems for the USCG operations against the prohibition violators and to decrypt the messages accumulating. The Friedmans were famous cryptographers with expansive careers in Washington DC for the U.S. army, navy, Treasury and Justice Departments throughout WWI and WWII. In 1927, the rum runners commonly used two coding systems, switching them every six months. By mid-1930, rum runners significantly increased their coding abilities having virtually every rum boat use its own coding system. From April 1929 to January 1930, the San Francisco intelligence collection station alone intercepted 3,300 messages and discovered approximately 50 distinct secret coding systems which varied with up to five subsystems of codes and ciphers used by the rum runners. Between 1927 and 1928, the USCG unit successfully reduced the flow of illegal smuggling by 60 percent, from 14 million gallons of liquor to 5 million, by breaking these coding systems. An example of their successes took place on 29 September 1930, when the unit intercepted a message sent by a shore station in Vancouver, British Columbia intended for a rum runner operating in the Gulf of Mexico. The coded message contained five columns of 3-4 words each. When decoded by the unit, the message read “Henry cannot take goods now. Proceed 50 miles east Briton Island and give to Louis when he comes.” Their successes were in part due to the USCG interception and decryption capabilities, and their innovation in fusing together all-source intelligence such as human intelligence (HUMINT), imagery intelligence (IMINT) and communications intelligence (COMINT). The cryptanalytic unit used USCG patrol boats with high-frequency direction finding gear (HFDF, also nicknamed “Huff Duff”) created by William Friedman, and Elizebeth's code-breaking expertise to locate illicit radio stations and rum runners at sea. The USCG today credits these operations as the first tactical law enforcement use of COMINT in U.S. history. Elizebeth alone decrypted approximately 12,000 messages between rum runner networks over a three-year time span. The unit decrypted a total of approximately 25,000 messages per year during prohibition. Following this success, the USCG requested that Elizebeth contribute more to their expanding operations, including codebreaking smugglers’ communications and aiding USCG partners such as the Customs Bureau and Secret Service. The U.S. Treasury Department officially transferred her to the Coast Guard in June 1931 to work as a cryptanalyst and to build up a new, official cryptanalytic unit within the Coast Guard. She began hiring and training young professionals to be cryptanalysts, women with expertise in stenography and men with backgrounds in physics, chemistry, or math. These young professionals trained in cryptanalysis officially became USCG Unit 387. The successful techniques in codebreaking and use of HFDF technology were later used by the unit in its clandestine operations in WWII, collecting information in Central and South America.
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