Code-breakers kept detailed lists, including, names of enemy ships and personnel. They used this information to help decipher codes. Codes had to be broken twice. The code-breakers would form an assembly line of girls to do this.
Female code breakers. Daily Press.Unknown.
Female Code breakers at work. WashingtonPost. Unknown.
When a code was broken it could be used for two different things, gaining information and sending a fake message in place of the code they just broke. Using the information gathered from these decoded messages was a balancing act. If they used too much of the information, like stopping a lot regarding ships, planes, or troops, the Axis powers would know the code-breakers had the key.