On July 9, 1941, British cryptologists help break the secret code used by the German army to direct ground-to-air operations on the Eastern front.

When did Enigma get declassified?

The story of Enigma (declassified in the 1970s) is well known, but the story of Tunny, Germany's top-secret cipher machine, was only declassified in the 2000s. Most of the cryptographers in the Testery died before they could tell their stories.

When was Alan Turing's work declassified?

The actual techniques Turing used to decrypt the messages weren't declassified until 2013, when two of his papers from Bletchley Park were released to the British National Archives.