It was in 1944 when Colossus officially came into operation, considered the first large-scale electronic computer. And he did it at a turbulent moment, in the middle of a World War that had already caused millions of deaths around the world, in order to read German encrypted communications using Enigma (transmitted in Morse code), and thus try to at least increase the chances of winning the war.
According to Winston Churchill , British Prime Minister, the arrival of this computer to the war allowed the war to be shortened by 18 months , since it offered the possibility of knowing details about the status of the enemy’s supplies, ammunition, the movement of troops, the number of soldiers killed, etc. It was capable of processing 5000 characters per second, an amount that was considered “colossal” for that time.
It was based on the idea of universality of the Turing machine , and was composed of more than 1500 vacuum tubes. Data entry was carried out using punch cards, and the results were temporarily stored on relays until they were output through a typewriter. It was 2.25 meters high, 3 meters long and 1.20 meters wide, and it was fully automatic.
Although it took around 10 months to build (from February to December 1943), it was at the beginning of World War II, in 1939, that the British Government decided to bring together some of the best scientists in Bletchley Park to help decipher the messages of the Germans.
Among them was Alan Turing , considered one of the biggest promoters of the project. In fact, it took care of, among other things, the logic functions of the machine. While the engineer Thomas H. Flowers was in charge of redesigning the machine’s counter by proposing that the data be stored in vacuum tubes.
His goal was to remove a first layer of encryption from the German message , comparing two data streams, and counting each match based on a Boolean programmable function. That encrypted message was read at high speed through a paper tape, and the other data stream was generated internally. From there, it offered the possibility for experts to more easily decipher the messages. In this way, the original role of Colossus was to perform calculations until reaching an intermediate point , since it was not able to perform a total decryption of the messages.
The result? It took the Allies barely four hours to decipher a message . In fact, such was its speed for the time that historians believe that the deciphered messages were read by the Allies before they actually reached the German military high command. And around 550 people were actively working to make this possible.
Thanks to its construction, the allies were able to find out that Germany expected the invasion of Europe through the Pas de Calais or Pas de Calés and not by Normandy, which allowed to validate the invasion plan through Normandy, which took place on June 6, 1944.
Once built, production accelerated rapidly, and the Birmingham Post factory manufactured the later Mark II Colossi, a new version capable of five times the processing power of the computer. But it also had a breakthrough: it eliminated the final manual step, so it was able to fully decrypt messages .
