The Nazis' secret weapon: Incredibly rare Enigma machine built AFTER Alan Turing's Bletchley Park experts cracked original code

Daily Mail​

2 days ago

An incredibly rare four rotor Enigma machine used by the Nazis during the Second World War has emerged for sale for £300,000.
The Nazis sent coded messages through the cipher machines to their ships and U-boats to plan devastating attacks on Allied shipping.
The British codebreakers at Bletchley Park, led by Alan Turing, cracked the original three rotor Enigma machines in 1941.
A subsequent dramatic fall in the number of Allied ships being sunk led the Germans to suspect the Enigma had been compromised.
As a result, in February 1942, they introduced a new fourth rotor wheel which multiplied the number of available settings another 26 times.
But the codebreakers at Bletchley were again able to crack it, enabling them to decipher a staggering 84,000 German messages a month.
Some experts believe their work may have shortened the war by up to two years.
Since the Nazi high command ordered the Enigma machines be destroyed towards the end of the war to prevent them falling into enemy hands, surviving examples are extremely scarce.
The rare surviving example of the improved M4 cipher machine is going under the hammer at auctioneers Bonhams, of Knightsbridge, London.
The machine - which measures 6ins by 11ins by 14ins - has three moving wired rotors, a fixed reflector and a plug board located behind a wooden flap at the front.
A Bonhams spokesperson said: 'The M4 differs from other models in that it has a fourth, additional but non-rotating and non-interchangeable rotor that increased the complexity of the enciphering process.
'It was the fourth naval model and was particularly intended for use by the U-boat division.
'Production of this model began in late 1941 and it was introduced early into 1942.
'With the increased complexity introduced by this model, the M4 came as a shock to Allied codebreakers and went unbroken for nine months, until the capture of important key sheets aboard the U-559 by British sailors in October 1942.
'Traffic enciphered by the M4 was codenamed SHARK by Allied codebreakers and this eventual breach of this communications channel played an important role in the Battle of the Atlantic.
'The German High Command ordered that Enigma machines be destroyed in the event that capture by Allied forces was imminent, so few survive today.
'The M4 is rarer than its Army counterpart, the Enigma I, with just 70-80 surviving examples of the M4 recorded worldwide, of which only about half are in private hands.
'The M4 offered by Bonhams is a very fine, well-preserved example.'
The sale takes place on September 9.
Turing remains the most high-profile of the Bletchley Park codebreakers, in large part because of his incredible feats and subsequent tragic fate.
The genius, who was gay at a time when homosexual relations were illegal, was convicted of gross indecency with a man in 1952.
He chose to be chemically castrated over going to prison and took his life just two years later aged 41.