Beckman, Bengt. Tr., Kjell-Ove Widman. Codebreakers: Arne Beurling and the Swedish Crypto Program during World War II. Providence, RI: American Mathematical Society, 2002.

Kruh, Cryptologia 27.3: "A magnificent accomplishment in the history of cryptography occurred in 1940 when a Swedish mathematician [Arne Beurling] broke the German cipher used for strategic military communications [Geheimschreiber].... This book provides a valuable contribution to the history of cryptology with much new information and added respect for the cryptanalytical achievements of Sweden's signal intelligence agency."

For Beard, I&NS 18.4, this work "is a more personal, and far more Swedish, companion" to Beckman and C.G. McKay's Swedish Signal Intelligence 1900-1945. (2002). One problem with the work is that "there is simply no political context" for the interception and decoding work.

Jörgensen, Christer. Spying for the Führer: Hitler's Espionage Machine. Minneapolis, MN: Chartwell Books, 2014.

For Peake, Studies 59.1 (Mar. 2015), this book offers "a broad overview of the German intelligence services from WW I to the end of WW II." It also discusses "Sweden's role in the war, including its secret attempts to broker peace."

McKay, Craig Graham. From Information to Intrigue: Studies in Secret Service Based on the Swedish Experience, 1939-1945. London: Frank Cass, 1993.

Herman, FILS 12.5, says that this "admirable book" looks at "Sweden as an intelligence battle ground and listening post" and at the "wartime development of Swedish cryptanalysis." It serves as an "introduction to an underestimated intelligence community in World War II." For Kruh, Cryptologia 18.2, "the major thrust of this excellent work ... is the variety of clandestine activities by foreign embassies and their intelligence staffs in Stockholm and the interplay between each other and their host.... With almost 600 footnotes and an extensive bibliography, this book is an excellent source for further research or reading."

According to Surveillant 3.4/5, From Information to Intrigue is an "illuminating and reliable account of some of the key activities of the Allied secret services and of their German counterparts in Sweden.... New light is shed on Siegfried Ascher, the spy in the Vatican.... Well documented and with an extensive bibliography."

Watt, I&NS 9.2, calls McKay an "assiduous comber-through of the open British and German materials.... But he has also used the published Swedish materials, and ... had access to Swedish archival materials, including ... some originating with the Swedish Security services.... [He] has [also] been able to tap a number of private sources.... [This is] one of the most useful and important books yet to appear on intelligence."

McKay, Craig Graham. "German Teleprinter Traffic and Swedish Wartime Intelligence." In Colossus: The Secrets of Bletchley Park's Codebreaking Computers, eds. B. Jack Copeland, et al., 328-336. Oxford & New York: Oxford University Press, 2006.

McKay, Craig Graham. "The Krämer Case: A Study in Three Dimensions." Intelligence and National Security 4, no. 2 (Apr. 1989): 268-294.

The author looks at the work of Karl-Heinz Krämer, of Abwehr Air Intelligence, in Stockholm from May 1941 to May 1945. The three dimensions used in surveying the activities of Krämer represent the German, British, and Swedish perspectives. McKay argues that Krämer "supplied various German central intelligence organs with a continuous flow of information."

McKay, Craig G., and Bengt Beckman. Swedish Signal Intelligence 1900-1945. London: Frank Cass, 2002.

Hess, JIH 3.1, calls this "an important account about ... Sigint as it developed in a medium-sized, neutral country of Europe.... This definitive, exhaustive and illuminating account draws on the official archives notably from Sweden and provides new and surprising results.... The centrepiece of the study ... is the Sigint contribution to Sweden's neutrality in two world wars, particularly in the second.... [T]he book is well presented and thoroughly edited."

For Van Nederveen, Air & Space Power Journal 17.3 (Fall 2003), this "first authoritative account of Sweden’s SIGINT [is] both valuable and unique.... The authors are to be commended for their detailed, up-front explanation of SIGINT: how radio and telegraph coding was used between various countries and their diplomatic missions, what kinds of transmissions third parties could intercept, and the numerous tasks involved in decoding that data.... SIGINT books are rare, and this one is a must-read for intelligence professionals.... Historians interested in World War II may even have to reconsider some events of that war after reading this book."

Kruh, Cryptologia 27.2, calls this work "a definitive account of the evolution of Swedish signal intelligence between 1900 and 1945.... It is an interesting and surprisingly revealing source of European cryptology in the first half of the twentieth century." To Erskine, I&NS 18.3, the authors "have researched their subject thoroughly and know it well." The work "deals mainly with the collection and breaking of messages and the establishment and organisation of the various bodies which were responsible for Sigint. It contains comparatively little on analysing the resulting intelligence, or how it was used by policy makers."

Molander, Pia. "Intelligence, Diplomacy and the Swedish Dilemma: The Special Operations Executive in Neutral Sweden, 1939-45." Intelligence and National Security 22, no. 5 (Oct. 2007): 722-744.

"SOE's organization in Sweden had a dual mandate, as much political as operational. Its primary function was to serve as an instrument for the use of regional SOE headquarters, and as a conduit for operations into Germany and axis-occupied territory.... [I]n the end it was decided the British diplomatic mission in Sweden was too important to be jeopardized by unrestricted espionage."

Olsson, Simon. "Beyond Diplomacy: German Military Intelligence in Sweden 1939-1945." International Journal of Intelligence and Counterintelligence 24, no. 2 (Summer 2011): 338-351.

"At the outbreak of the war in 1939, the Abwehr was well prepared..., with a network of informants all over Sweden. The results during the war would, however, be mixed."

Tennant, Peter.

1. "Swedish Intelligence in the Second World War." Intelligence and National Security 2, no. 3 (Apr. 1987): 354-361.

2. Touchlines of War. Hull: University of Hull Press, 1992. Boston: Park & Co., 1992.

Ulfving, Lars, and Frode Weierud. "The Geheimschreiber Secret: Arne Beurling and the Success of Swedish Signals Intelligence." At:

In World War II, "the breaking of the cipher from the German Enigma machines and the Japanese Purple machines [footnote omitted] was of crucial importance. The considerably greater intellectual effort needed to break the Geheimschreiber messages, which was accomplished in Sweden, did not in any way have the same decisive significance for the war. Therefore this accomplishment has not been so well known. However, from a Swedish perspective, it was of considerable importance as it actively contributed to keep Sweden out of the war."

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