Wennerström was born on 22 August 1906 in Stockholm, Sweden, the son of major Gustaf Wennerström and his wife Ester Berggren. He passed studentexamen in 1926 and became fänrik in the Swedish Navy in 1929 and conducted flight training from 1931 to 1932. Wennerström was promoted to löjtnant in the Swedish Air Force in 1936 and completed the Royal Swedish Naval Staff College's staff school from 1936 to 1937. He was aide-de-camp to Prince Gustaf Adolf, Duke of Västerbotten from 1938 to 1947 and was promoted to captain in 1939 and served as air attaché in Moscow from 1940 to 1941. Wennerström was promoted to major in 1944 and to lieutenant colonel in 1946. He was a teacher at the Royal Swedish Air Force Staff College from 1946 to 1948 and was again air attaché in Moscow from 1949 to 1952. Wennerström was promoted to colonel in 1951 and served as air attaché in Washington, D.C. from 1952 to 1957. He was section chief at the Military Office of the Minister of Defence from 1957 to 1961. During the 1950s, Wennerström leaked Swedish air defence plans and the entire Saab Draken fighter jet project to the Soviet Union. When working as an air attaché in Washington, D.C., he was very useful to the Soviet military intelligence agency, the GRU. As early as 1943, the Swedish Security Service, suspected that Wennerström was working for Germany and in 1947 there were indications that he had connections with the Soviet Union, but the suspicions couldn't be proven. The counterintelligence operation centred on him was intensified towards the end of the 1950s and his household maid was recruited by SÄPO. In June 1963, the maid reported that she had found some film rolls hidden in his attic. The films contained photographs of secret documents.
Arrest and conviction
In the morning of 30 June 1963, Wennerström was on his way to his work at the Ministry for Foreign Affairs in central Stockholm. Just as he passed the Riksbron Bridge, three people from SÄPO came up behind Wennerström and arrested him. After his arrest, Wennerström was brought to SÄPO's premises on Bergsgatan in Kungsholmen, where the hearings began immediately. At the same time, Wennerström's house on Skirnervägen 20 in Djursholm was locked for a search warrant that would take almost a week. Initially, Wennerström denied the charges. At the same time, SÄPO failed to develop the film rolls containing Wennerström's photographs of secret documents. An expert was called in, and after three and a half days, found the right method. When the photographed documents were displayed to Wennerström, he confessed, but at the same time denied that his spying had been directed against Sweden. Soon, however, he was convinced. During the six years prior to his arrest, Wennerström is believed to have handed over 20,000 pages of secret documents about the Swedish defences. The documents contained information about the Swedish Air Force's strategy, secret military bases, and radar defense and mobilization plans. Wennerström was initially sentenced to life in prison, the most severe peacetime sentence. In 1972 the Swedish government commuted the sentence to 20 years, despite the Supreme Commander, GeneralStig Synnergren, still considering him to be a high security risk. He was paroled in 1974 after serving a total of 10 years; the norm in Sweden at the time was to release prisoners after they had served half their sentences.
Personal life
In 1939 he married Ulla-Greta Carlsson, the daughter of consul Eric Carlsson and Helga Andersson. He had two daughters. Wennerström died on 21 March 2006 at the retirement home Tallgården in Enebyberg, north of Stockholm. The funeral took place on 28 March 2006 at Altorp's Cemetery Chapel in Djursholm and he was buried on 3 May 2006 at Djursholm's Cemetery.
