Communications without secrets. Activities of Spanish listening and cipher services during two wars (1939–1945)

The appearance of radio communications supposed a revolution in the commercial field and also in the military field. Problems for information coordination and distribution disappeared due to the great simplicity of the wireless telegraphy. Moreover it was possible to avoid rigid and costly infrastructures that limited, in many cases, the correct use of communications. However the flexibility and the independence of a tangible physical media represented a potential danger: the capture and use of this information by non authorized people or organizations (so called illegal listening or eavesdropping). Spanish civil war and World War II showed the great importance of the eavesdropping services, used by all the contenders and by third countries interested in the Spanish situation. Some of these third countries were also interested in using Spain for their spying networks. Many historians said that Spanish war was a test field. If this is true, the German and soviet eavesdropping services were good pupils, although possibly the Italian services were the most active and useful. The Spanish services were excellent pupils obtaining a very high technical competence, even worthier thinking in the null technical knowledge at the beginning of the war. In fields as cryptanalysis, Spanish services were better many times than their supposedly teachers, allowing the rebel camp to be perfectly informed of the international situation once finished the Spanish war. During World War II the foreign eavesdropping services at Spain, mainly German and Italian, followed their work, sometimes collaborating with their Spanish counterparts. The ciphering services tried to reduce the danger associated with these eavesdropping, an objective not always got. This work aims to offer a broad view of the conduct of the eavesdropping, ciphering and cryptanalytic services, Spanish and foreign, during this period. Also we analyze their organization, effectiveness and achievements and failures during the tumultuous years since 1936 until 1945.