At the beginning of World War II, he was in Paris, studying the viola with the French violist Maurice Vieux. Pettersson won the Jenny Lind scholarship prize in 1938, using it to study abroad. Later life During the 1940s he worked as a violist in the Stockholm Concert Society (later the Royal Stockholm Philharmonic Orchestra). He also studied composition with the composer and conductor Karl-Birger Blomdahl, orchestration with the conductor Tor Mann, and counterpoint with organist and composer Otto Olsson. In 1943, he married a physiotherapist, Gudrun Tyra Charlotta Gustafsson (1921–2017). In September 1951, he went to Paris to study composition and was a student of composers René Leibowitz, Arthur Honegger, Olivier Messiaen, and Darius Milhaud. Pettersson returned to Sweden at the end of 1952. In the early 1950s, he was diagnosed with rheumatoid arthritis. He gave up playing the viola and began devoting his life to composition. In 1954, Pettersson received an annual state composition grant for his first time. By the time of his Symphony No. 5, completed in 1962, his mobility and health were compromised considerably. In 1964, the government granted him a lifelong guaranteed income. His greatest success came a few years later with his (1966), which premiered on 13 October 1968 in Stockholm Concert Hall with Antal Doráti conducting the Stockholm Philharmonic Orchestra. A recording of his seventh symphony, with the same conductor and orchestra, was released in 1969. It was a breakthrough, establishing his international reputation, and he received two Swedish Grammis in 1970. The conductors Antal Doráti and Sergiu Comissiona premiered and made first recordings of several of Pettersson's symphonies and contributed to his rise to fame during the 1970s. Pettersson was hospitalized for nine months in 1970, soon after the composition of his Symphony No. 9, his longest symphony. He began writing the condensed Symphony No. 10 (1972) from his sickbed. Pettersson was admitted to Karolinska Hospital, because of a life-threatening kidney ailment. He recovered, but rheumatoid arthritis confined him most of the time to his fourth-floor apartment in a building with no elevator. In 1975, after a dispute about a change in a concert program for an American tour, the Stockholm Philharmonic was forbidden to perform works by Pettersson "for all time". The ban was lifted in 1976. Pettersson was awarded the Litteris et Artibus, a Swedish royal medal established in 1853, in 1977. In autumn 1978, he moved to a