Skip to main content

Role and effectiveness of signals intelligence during World War II

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

This series of short narratives (PDF) demonstrates the important role and level of effectiveness that SIGINT provided 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
  • the Battle of the Atlantic
  • the 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 who is 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)