During World War II Nazi Germany primarily encoded its messages through the use of what was known as the "Enigma" machine. Enigma’s use by the Wehrmacht stretched back to the early 1930s and originated from a design created by Hugo Alexander Koch in the Netherlands.
Although heavily modified prior to the Second World War’s onset, the Enigma machines used in 1939-1945 remained similar to Koch’s prototypes from two decades prior. For a variety of reasons the Enigma machine was extraordinarily difficult to crack.
One of the great Allied advantages over Nazi Germany during World War II was their ability to regularly intercept and read otherwise encoded German communications. Though this capability was not comprehensive, with changes to the German code settings throwing the Allies off at repeated times during the war, it proved of significant assistance to the Allied war effort. Some believe Allied code-breaking efforts were so consequential as to have decisively altered the course of the war.
The central location for Allied code breaking efforts was at Bletchley Park, northwest of London.
