The impact on the war
Germany used the Enigma machine for all sorts of communications. This included secret information about its military plans. Cracking the Enigma codes meant the British military could keep British ships away from German ships, and predict where German planes might bomb. Information gathered from these codes was nicknamed Ultra, and was top secret. However, not every German attack could be prevented, because then the Germans might guess that their codes has been cracked. As a result, some attacks that could have been prevented still went ahead.
Winston Churchill (left), the UK’s wartime leader, in 1940.