Larsson was born on 14 September 1934 in Lund City Parish (Lunds stadsförsamling), Sweden,[1] the son of Lennart Larsson, a farmer, and his wife Kristina (née Bengtsson).
Larsson served in South Scanian Regiment from 1976 to 1977 and in the Southern Military District from 1977 to 1979 and then attended the Swedish National Defence College in 1979.
[2] In 1983, Larsson attended a staff course in Monterey, California, United States and at the Swedish National Defence College.
He served in this position for five years before being head of the Swedish National Defence College from 1988 to 1994.
[2] Larsson was an expert in the Swedish Armed Forces Management Investigation (Försvarets ledningsutredning, FLU 74) and in the 1979 Materiel Procurement Commission (1979 års materielanskaffningskommission), chairman of the Swedish Pistol Shooting Association (Svenska pistolskytteförbundet) from 1984 to 1989, chairman of the Swedish Military Sports Association (Sveriges militära idrottsförbund) from 1984, and a board member of the Swedish Ancestry Research Association (Sveriges Släktforskarförbund).