A counterintelligence example describes British knowledge that Germany had broken a British code. The response was to leave that code unchanged for roughly three months. An immediate change could have revealed that the German success had been detected. The particular code and dates are not supplied, so the example supports the concealment rationale without establishing a precise chronology.
Notable Point · 1:32:43-1:33:15
Delaying a code change to conceal an intelligence success
An unspecified compromised British code illustrates why an immediate security response could reveal knowledge to the enemy.