Another interesting code breaker during WWII was the Swede Arne Beurling (https://en.wikipedia.org/wiki/Arne_Beurling https://en.wikipedia.org/wiki/Arne_Beurlin

Another interesting code breaker during WWII was the Swede Arne Beurling (https://en.wikipedia.org/wiki/Arne_Beurling https://en.wikipedia.org/wiki/Arne_Beurling). He reverse-engineered the Sturgeon cipher from intercepted enrypted texts using pen and paper only, enabling Sweden to break the cipher systematically. On the other hand, this had little impact on WWII as a whole, so it is not as important as the code breaking done at Bletchley park.