Role and effectiveness of signals intelligence during World War II

Signals intelligence (SIGINT) made a decisive contribution to the successful outcome of World War II for the Allies. SIGINT featured prominently across both the European and Pacific theatres.

This series of short narratives (PDF) demonstrates the important role and level of effectiveness of SIGINT for the Allies during World War II. SIGINT contributed to successes such as the:

  • Battle of Midway Island
  • tactical air raid warnings in the South-West Pacific
  • Battle of the Atlantic
  • ability of Allied forces to significantly impact the effectiveness of the Japanese Army Air Force in New Guinea and Japanese merchant shipping.

SIGINT contributed to Allied planning for the Normandy landings and the Battle of France, revealed details of German scientific weapons and apparatus, and was a critical capability in the Battle of Cape Matapan, the Balkans and Crete campaigns, the war in North Africa, and the closing phases of the Nazi defeat.

The second document in this series is a signal message (PDF) intercepted by 6 Wireless Unit (6WU) on 6 January 1945. The message is from a Japanese pilot warning the Japanese higher command of the sighting of Allied shipping, believed to be the Lingayen invasion fleet.

The invasion of Lingayen Gulf between 6–9 January 1945 was an Allied amphibious operation in the Philippines during World War II.


Role and effectiveness of Signals Intelligence in World War II (PDF)

6 Wireless Unit signal sighting of Allied shipping, 6 January 1945 (PDF)

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Acknowledgement of Country

We acknowledge the Traditional Owners and Custodians of Country throughout Australia and their continuing connections to land, sea and communities. We pay our respects to them, their cultures and their Elders; past, present and emerging. We also recognise Australia's First Peoples' enduring contribution to Australia's national security.

Authorised by the Australian Government, Canberra