The men at Station HYPO under Joseph Rochefort are the ones who deserve the most credit. They broke JN-25. Thanks to them we knew the Japs were going to attack at Midway on 4 June with Kaga, Akagi, Hiryu and Soryu.
The Japanese had every inking that we had broken their code during the war, but were too racist to believe that Caucasians could do this.