Hakkila was elected into Parliament for terms of 1919–1945 and 1948–1958. He was deputy speaker from 1929 to 1932 and speaker of the Parliament from 1936 to 1945, including wartime period. He was Minister of Justice in the Tanner Cabinet from 1926 to 1927 and the first Social Democratic municipality mayor of Tampere for more than thirty years, 1920–1952.
Hakkila, as one of the victims of Lapua Movement, was kidnapped and beaten in July 1930.
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