Bletchley Park - Second World War

Second World War

The first wave of the Government Code and Cypher School (GC&CS) moved to Bletchley Park on 15 August 1939. The main body of GC&CS, including its Naval, Military and Air Sections, was on the ground floor of the mansion, together with a telephone exchange, a teleprinter room, a kitchen and a dining room. The top floor was allocated to MI6. The prefabricated wooden huts were still being erected, and initially the entire "shooting party" was crowded into the mansion, its stables and cottages. These were too small, so Elmers School, a neighbouring boys' boarding school, was acquired for the Commercial and Diplomatic Sections.

Both of the two German electro-mechanical rotor machines whose signals were decrypted at Bletchley Park, Enigma and the Lorenz Cipher', were virtually unbreakable if properly used. It was poor operational procedures and sloppy operator behaviour that allowed the GC&CS cryptanalysts to find ways to read them.

The intelligence produced from decrypts at Bletchley was code-named "Ultra". It contributed greatly to Allied success in defeating the U-boats in the Battle of the Atlantic, and to the British naval victories in the Battle of Cape Matapan and the Battle of North Cape. In 1941, Ultra exerted a powerful effect on the North African desert campaign, against the German army, under General Erwin Rommel. General Sir Claude Auchinleck stated that, but for Ultra - "Rommel would have certainly got through to Cairo". Prior to the Normandy landings on D-Day in June 1944, the Allies knew the locations of all but two of the 58 German divisions on the Western front. Churchill referred to the Bletchley staff as "The geese that laid the golden eggs and never cackled".

When the United States joined the war, Churchill and Roosevelt agreed to pool resources. A number of American cryptographers were posted to Bletchley Park and were inducted and then integrated into the Ultra structure, being stationed in Hut 3. From May 1943 onwards there was very close cooperation between the British and American military intelligence organisations. Conversely, the existence of Bletchley Park, and of the decrypting achievements there, was never officially shared with the Soviet Union, whose war effort would have greatly benefited from regular decrypting of German messages relating to the Eastern Front. This reflected Churchill's concern with security, and his distrust of and hostility to communism, even during the alliance imposed on him by the Nazi threat.

The only direct enemy action that the site experienced was when 3 bombs, thought to have been intended for Bletchley railway station, were dropped on 20–21 November 1940. One exploded next to the despatch riders' entrance, shifting the rear end of Hut 4 (the Naval Intelligence hut) two feet on its base. As the huts stood on brick pillars, workmen just winched it back into position while work continued inside.