// The /fun Collection · Signals War //
Enigma_
Press a key and a different letter lights up. Press the same key again and yet another lights, because the rotors turned between the two. This is a working Enigma I with the real rotor wirings. The diagram at the bottom shows the thing the operators never saw: the current itself, threading the maze.
Opening the case… ▊
Why it fell
The machine offered around 159 quintillion daily settings, and the Wehrmacht believed that ended the argument. But the reflector that made the machine self-inverse also guaranteed no letter could ever encrypt to itself, and operators fell into habits: repeated headers, predictable weather reports, the same greeting every morning. Polish mathematicians broke the machine first in 1932 and handed Britain their work as the war opened. At Bletchley Park, Turing's bombes turned those flaws into a daily harvest the Germans never suspected.
Try it above: type any letter over and over and watch it never come back as itself. That absence, a letter that refuses to be itself, was a crack wide enough to drive a war through.
Sources
A /fun project. More machines in the collection: SAGE · Nike Missile Explorer · Thirteen Days