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World War 2 Wireless Intercept – Reading the Mail

world war 2 wireless intercept

World War 2 Wireless Intercept is the story of the people and technologies that fought our first electronic war, and took signals intelligence to a whole new level. 

People became aware of World War 2 wireless intercept with publication of The Ultra Secret in 1974. Since then, much has been written about the Bletchley Park code-breakers, and the importance of Ultra. Secrecy had lasted over 30 years. Now, you can read dozens of books, and watch many television shows and movies about decoding Enigma.

Revealing the Ultra Secret was sensational. According to an article in the Journal of the U.S. Army War College: “It was sweeping, especially, in the sense of seeming to demand immediate and wholesale revision of historical assumptions about virtually all that determined the course of World War II in the Atlantic sector. It astonishes one to reflect on how little speculation there had been hitherto about the extent of code breaking on the part of the Western Allies and how few pressures there had been on governments to answer perplexing questions.”

But as you think about the genius of Alan Turing and his colleagues in Hut 8, consider this question: Who provided the millions of intercepted messages to Bletchley Park in the first place?

The Y Service provided these messages. Y is short for “wireless intercept”. World War 2 wireless intercept is the other half of the SIGINT story, about which nearly nothing has been written. I will change that with a series of articles digging into how the technical side of radio interception worked. Sort of the boiler room which provided material to the scientists and soldiers.

World War 2 Wireless Intercept – A Look Ahead

Between 1939-1945, tens of thousands of soldiers, civilians and volunteers spent around a billion hours monitoring radios. Some sat in their homes listening to ham receivers. Some were located in fixed monitoring stations along English and American coast lines, as well as places as far away as Bangalore and Winnipeg. Many were in field listening posts close to the front lines, aboard ships or in the air.

The British and Germans were most advanced in SIGINT and the U.S. caught up quickly. Radio was the life blood of military command and control, across the total spectrum of radio frequencies. World War 2 could not have been fought without the span of distance and force mobility provided by wireless. It could not have been won without the benefits of interception.

Now, get this. Decoding encrypted messages is only a small (albeit important) part of signals intelligence. Of equal value were techniques such as traffic analysis and direction finding. Even encrypted messages provide information if you know how to study the people and processes that transmit them.

Radio listeners typically did not know what they were hearing, unless in plain text or low-grade codes. But they logged these messages in detail. Analyzing the logs, even without decryption, provided tactical and operational intelligence that made a huge difference in the war effort. And that is the story we shall tell in future articles.

World War 2 Wireless Intercept – Other Sources

To get started, watch this rare BBC documentary The Secret Listeners from 1979.

Three books have been written on this subject. These include The Searchers: Radio Interception in Two World Wars in 2003 and The Secret Listeners in 2012. The Searchers is good from a military historian’s perspective. Secret Listeners is a story about the people involved. Neither is very technical, but worth reading. On the German Side, you might enjoy German Radio Intelligence, an online history provided by Lieutenant-General Albert Praun.

Stay tuned…

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