Born Oct. 28, 1899, in Malmberget, in the Iän (county) of Norrbotten. Figure in the Swedish working-class movement.
The son of a worker, Hagberg worked in the iron mines of Kiruna from 1912 to 1929. He joined the Social Democratic Party of Sweden in 1914 and the Left Social Democratic Party of Sweden in 1917; from 1921 to 1967 the latter was called the Communist Party of Sweden (CPS). From 1930 to 1967, Hagberg was a member of the Central Committee of the CPS, renamed the Administrative Board in 1964. From 1933 to 1967 he was a member of the Politburo of the Central Committee of the CPS, renamed the Executive Committee of the CPS in 1964. Hagberg was acting chairman of the CPS in 1949 and 1950 and chairman from 1951 to 1964. From 1943 to 1945 he was political editor of the central organ of the CPS, the newspaper Ny dag. He served as a deputy to the Riksdag from 1933 to 1964. Hagberg was a delegate to the Fourth Congress of the Profintern, held in 1928, and to the Seventh Congress of the Comintern, held in 1935.