Why did Enigma’s rotating wheels make its messages difficult to decipher?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Ultra The British government established a code-breaking effort, known as Ultra, at Bletchley Park in Buckinghamshire, England, during World War II.

The Enigma machine’s rotating wheels made its messages difficult to decipher because they created an ever-changing pattern of electrical connections. As a cipher clerk typed a message, the internal wiring passed through these rotating wheels, which shifted positions with each keystroke.1

This mechanism meant that the same letter typed repeatedly—such as "AAAA"—would result in a different output letter each time, such as "WMEV". Because the connections were constantly altering as the wheels moved, the machine produced a complex, shifting cipher that was extremely challenging to break. Furthermore, the difficulty was compounded by the vast number of permutations available, as operators regularly changed the machine's wheel and plugboard settings based on daily orders.12