For thirty years after the Second World War, historians said very little about the role of signals intelligence in the Battle of the Atlantic—because either they did not know about the Allies’ remarkable code-breaking successes, or they could not write about what they did know. That changed in 1974, when revelations about ULTRA exposed the full extent of the Allied penetration of Germany’s sig- nals. Unfortunately, in the subsequent rush to rewrite the history books to in- clude ULTRA, its significance was fre- quently inflated.
"Decoding History: The Battle of the Atlantic and Ultra,,"
Naval War College Review: Vol. 54
, Article 26.
Available at: https://digital-commons.usnwc.edu/nwc-review/vol54/iss3/26