Why did German and Japanese leaders fail to realize that their codes were compromised?
Short answerIt was a mixture of leadership, organizational, and cultural failure reinforced by confidence that mathematically difficult systems were unbreakable.
NotesNo single cause explains why German and Japanese leaders failed to recognize compromised codes. Leadership, organization, and culture all contributed. Codebreaking was an active contest throughout the war, but non-specialists often believed a system was unbreakable because its mathematics appeared formidable. Confidence in the technology and in expert assurances therefore discouraged commanders from treating enemy foreknowledge as evidence of a security failure.