Since its founding in 1790, the U.S. Coast Guard fought in many of our major conflicts, provided vital search and rescue services, and protected our nation’s shores from smugglers and terrorists. One of that service’s epic battles began just over 100 years ago with the passage of the 18th Amendment.

Popularly known as Prohibition, the new law forbade the import or manufacture of alcoholic beverages in the U.S. Predictable results followed its opening kickoff. British and Canadian distilleries ramped up to full production and the smuggling race was on.

Motherships ran blacked out and anchored just outside territorial waters.

Seagoing smugglers loaded up motherships for rendezvous with small speedboats just outside U.S. territorial waters. Coast Guard’s task was a daunting one. A limited number of cutters had to cover thousands of miles of coastline. And modern navigation aids were virtually nonexistent. No GPS, no LORAN, no radar … just celestial and DR (dead reckoning). Busts were almost a matter of chance encounter.

Initially, smugglers were small groups of opportunists. By the late 1920s, large criminal syndicates had recognized the huge potential profits and had virtually taken over. A corresponding orchestra of radio messages hit the ether [1] as they coordinated shipment and rendezvous.

Small speedboats dashed out to the motherships to load up.

Coast Guard astutely recognized the mob’s new orchestra as a potential achilles heel and began working with labs and industry to develop a new series of direction finders.

Coast Guard Type X portable direction finder.

What followed was a series of shore based coastal DF sites along with a variety of portable units. Impressive, considering that direction finding was still in its infancy.

Some of the first smuggler shore stations tried to pass themselves off as amateur radio operators. They used amateur like callsigns and procedures on air. Some even had neatly arranged home stations complete with QSL cards on the wall [2]. I didn’t find any info on whether real hams were involved. I did find, however, that the bad guys were paying their head radio op $10,000 a year, a huge sum in 1930. With the Depression in full swing, you can imagine the level of temptation.

Law enforcement teams with their new portable direction finders hustled to locate and bust shore stations when they were active. If you’ve ever tried mobile HF hunting, you know this is no small task …

75 ft patrol boat like the one used for HFDF trials.

Meanwhile, shore based DF sites went after the motherships, hoping to achieve a fix and vector the nearest cutter to the scene in time for a bust. Another innovation from the team, shipboard DF, improved their odds significantly. Coast Guard managed to “borrow” Army civilian William Friedman and installed a DF system aboard one of their 75 foot patrol boats. Results were impressive. Shipboard DF offered both cutoff bearings to the shore sites and the ability to follow a bearing to a bust. (Friedman is better known as leader of the Army Signal Intelligence Service (SIS) team which solved the WWII Japanese diplomatic cipher machine and later as an NSA plank owner.)

For a successful bust, the Coast Guard cutter still needed to be close enough to the DF fix to catch the speedboats loading before they dashed to shore to unload. What if they could obtain advance knowledge of the rendezvous and set up an ambush? Doing so would require breaking the rum runners’ codes.

As the rum running syndicates grew in size and sophistication, so did their encryption, progressing from simple substitution to more advanced ciphers with different keys for each group. Hundreds of daily intercepts soon overloaded Coast Guard’s few self-taught cryptanalysts. Army’s SIS turned down a request for assistance, wary of being a military outfit drawn into civilian law enforcement.

Elizebeth Friedman

Enter Elizebeth Friedman, wife of William Friedman and top notch cryptanalyst. Brought onboard in a civil service position, she and her team soon achieved remarkable success. Her courtroom testimony was instrumental in convicting senior syndicate members. And her response to scrutiny by one of Washington’s infamous bean counters was legendary. Pointing out her team’s successes, she coolly noted that her entire annual budget was less than the price of one tank of fuel for a Coast Guard cutter.

Washington finally threw in the towel on Prohibition in December of 1933. But Coast Guard’s effort was hardly wasted. As the first hint of war clouds gathered over Europe and Asia, Navy inherited a number of the well calibrated and smoothly functioning shore based DF sites. And the lessons learned from portable direction finders would prove valuable in chasing Axis agents. When war broke out, Coast Guard became part of the Navy and its well trained team continued its cryptanalysis efforts.

Elizebeth and William Friedman were honored by induction into NSA’s Cryptologic Hall of Honor, along with Coast Guard cryptologist Captain Leonard Jones. And the Friedman’s each have an auditorium named in their honor – Elizebeth at ATF (Alcohol Tobacco and Firearms) and William at NSA. Coast Guard once again acknowledged the importance of its cryptologic mission with establishment of Coast Guard Cryptologic Group in 2007.

References and further reading:

1. Bowdoin, Charles: Waterways of Innovation: The Marine Technological Advancements of America’s Prohibition Era Thesis, Master of Arts in Maritime Science January 2016 East Carolina University Institutional Repository:

2. Lee, Bartholomew KV6EE: Radio Spies – Episodes in the Ether Wars California Historical Radio Society 2002, 2006:

3. Ensign, Eric LT, USCG: Intelligence in the Rum War at Sea 1920-1933 Joint Military Intelligence College 2001:

4. Mowry, David: Listening to the Rumrunners: Radio Intelligence During Prohibition: National Security Agency Center for Cryptologic History 2014

By Mr. Jeff Fuller