Early 20th century communications interception in Spain: a historical perspective

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COMINT (communications intelligence) activities involving the interception and surveillance of Spanish communications from the British colonial outpost of Gibraltar have been an integral part of British intelligence activities for centuries, particularly during the 1st and 2nd world wars, and the Spanish Civil War. In spite of Spain's neutral stance during World Wars I and II and its lack of prominence in world affairs, a chapter written by Arturo Quirantes Sierra in the book "Libertad Vigilada", published in 2003 by the journalist Nacho García Mostazo, which is based on documentation from the British Public Records Office, claims that Spain's "geographic location, its importance as a regional power and the upheavals that it experienced both within and outside its frontiers made Spain an important target for the surveillance of telecommunications". The importance of "secondary countries" in COMINT activities has been described as a "window effect", which provides a "stepping stone to get to know the movements and strategies of the leaders of other powers". This process would become particularly intense during World War II, due to the close relations between General Franco's regime and the Third Reich.

After noting that as far back as the late 16th century British agents were already intercepting and decoding messages between the Spanish emperor Felipe II and Don Juan of Austria, the Spanish governor of the Netherlands, alerting them of the emperor's belligerent intentions - thus contributing to the defeat of the Spanish Armada by the British - Quirantes documents the extent of British surveillance activities targeting Spanish communications in the early 20th century. During the first world war, the interception of coded diplomatic correspondence concerning reparations to be paid to Spain by Germany for commercial losses resulting from the submarine war declared by Germany in response to a British blockade of Germany, between the Spanish monarch Alfonso XIII and the Spanish embassy in Berlin, gave Britain access to privileged information. In this instance, the information included German plans to intensify its submarine warfare operations, and other issues including the loss and retrieval of documents from a German submarine in the south-eastern port of Cartagena, the possibility of Spain selling ships to countries involved in the war, and German concerns over the treatment of its POWs in France.

Other facets of British surveillance activities in the Iberian peninsula included the monitoring of Spanish-Portuguese relations (Portugal being a longstanding British ally in the region) and the interception of Spanish communications concerning North Africa, which gave British agents an idea about the intentions of France, its traditional colonial adversary, as well as a military advantage, as they included Spanish reservations concerning the presence and position of the British and French naval fleets in the Mediterranean. The Spanish Civil War was another conflict that attracted the interest of the British intelligence services, with the British obtaining "detailed daily updates on the situation in the conflict". Quirantes describes the breadth of information received by the RAF (Royal Air Force) alone as "encyclopaedic", including exhaustive knowledge of the location and contents of the main arsenals and bases, down to the last bomb, airplane or cartridge. The importance of these intelligence activities was heightened by the fact that the Spanish Civil War proved an important testing ground for weapons and tactics that were later to be used in World War II. For example, a message intercepted on 27 October 1936 ordered the urgent delivery of gas masks from the Nationalist Air Force General Command to the airfield in Talavera, in the province of Toledo.

The main interception centre for Spain was in Gibraltar, and it was the critical site for surveillance of Spanish communications. Communications between Ceuta (in north Afric

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