Socialist Workers' Party of Germany
He was originally a member of the SPD, but in the 1930s, he became a member of the Socialist Workers' Party of Germany, the Young Communist League of Germany and the Communist Party of Germany. During the Nazi era, he was active in the anti-Nazi resistance, and was imprisoned from 1936 to 1939 as a political prisoner. In 1942, he was conscripted into the 999th Light Afrika Division, a penal military unit. He was taken prisoner of war by the Americans in 1943 and repatriated in 1946. After the war, he became a member of the SPD again and became active in the IG Metall union. He was elected chair of the works council of AG Weser, his employer, in 1951, and served in this capacity until 1979. The election of Böhrnsen, a social democrat, to this position, meant the communists were finally ousted from influence in the works council.