History
Codebreakers let the US Navy ambush Japan's fleet at Midway
In June 1942, US Navy cryptanalysts had partly broken Japan's naval code and correctly worked out that Midway Atoll was Japan's next target, letting Admiral Chester Nimitz position his carriers in wait. Over four days, Japan lost all four carriers it had sent — Akagi, Kaga, Sōryū and Hiryū — along with their veteran aircrews, ending Japan's naval expansion and handing the Pacific's strategic initiative to the United States.