Im reading this currently: https://m.usni.org/magazines/navalhistory/2009-12/how-japanese-did-it https://m.usni.org/magazines/navalhistory/2009-12/how-japane...

Im reading this currently: https://m.usni.org/magazines/navalhistory/2009-12/how-japanese-did-it https://m.usni.org/magazines/navalhistory/2009-12/how-japane... According to this, their crypto was not completely broken, and the Japanese were very careful in shrouding their shift in strategy and attack plan from both the radios and other forms of communications.