Researching Hans Koster

De Koster attended a Gymnasium in Leiden from May 1927 until June 1933 and applied at the University of Amsterdam in June 1933 majoring in Economics obtaining an Bachelor of Economics degree in June 1935. De Koster worked as a corporate director for the flour manufacturer De Koster & Co in Leiden from April 1937 until May 1940. On 10 May 1940 Nazi Germany invaded the Netherlands and the government fled to London to escape the German occupation. De Koster joined the Dutch resistance against the German occupiers and founded and led the resistance cell Peggy. Following the end of World War II De Koster worked as a civil servant for the Diplomatic service of the Ministry of Foreign Affairs as an Attaché at the League of Nations in New York from June 1945 until April 1946. De Koster again worked as a corporate director for the flour manufacturer De Koster & Co from April 1946 until February 1967 and was Chief executive officer (CEO) from January 1947 until September 1964. De Koster also worked as a trade association executive for the Industry and Employers' association (VNO) from April 1956 until February 1967 and served as Vice Chairman of the Executive Board from 12 March 1958 until 18 May 1961 and as Chairman of the Executive Board from 18 May 1961 until 12 June 1967 and served as a Member of the Social and Economic Council from 1 April 1958 until 23 February 1967. De Koster also served as President of the Confederation of European Business from 1 May 1962 until 12 June 1967.

De Koster was elected as a Member of the House of Representatives after the election of 1967, taking office on 23 February 1967. Following the cabinet formation of 1967 De Koster was appointed as State Secretary for Foreign Affairs in the Cabinet De Jong, taking office on 12 June 1967. After the election of 1971 De Koster returned as a Member of the House of Representatives, taking office on 11 May 1971. Following the cabinet formation of 1971 De Koster was appointed as Minister of Defence in the Cabinet Biesheuvel I, taking office on 6 July 1971. The Cabinet Biesheuvel I fell just one year later on 19 July 1972 and continued to serve in a demissionary capacity until the first cabinet formation of 1972 when it was replaced by the caretaker Cabinet Biesheuvel II with De Koster continuing as Minister of Defence, taking office on 9 August 1972. After the election of 1972 De Koster again returned as a Member of the House of Representatives, taking office on 1 February 1973 but he was still serving in the cabinet and because of dualism customs in the constitutional convention of Dutch politics he couldn't serve a dual mandate he subsequently resigned as a Member of the House of Representatives on 1 May 1973. The Cabinet Biesheuvel II was replaced by the Cabinet Den Uyl following the second cabinet formation of 1972 on 11 May 1973 and he subsequently returned as Member of the House of Representatives, taking office on 28 May 1973 serving as a frontbencher and spokesperson for Foreign Affairs, European Affairs, NATO and Defence. De Koster also served as President of the Benelux Parliament from 1 January 1975 until 1 January 1976. In April 1977 De Koster announced that he wouldn't stand for the election of 1977 but wanted to run for the Senate and continued to serve until the end of the parliamentary term on 8 June 1977. De Koster was elected as a Member of the Senate after the Senate election of 1977, taking office on 20 September 1977 serving as a frontbencher chairing the parliamentary committee for Foreign Affairs and spokesperson for Foreign Affairs, European Affairs, NATO, Benelux, Defence and Veterans' affairs. De Koster also served as President of the Parliamentary Assembly of the Council of Europe from 1 January 1978 until 1 January 1981. In April 1980 De Koster was nominated as Extraordinary Member of the Council of State, he resigned as a Member of the Senate the same day he was installed as a Member of the Council of State, serving from 16 May 1980 until 16 May 1985.

De Koster retired after spending 18 years in national politics and became active in the private sector and public sector and occupied numerous seats as a corporate director and nonprofit director on several boards of directors and supervisory boards (Randstad Holding, Douwe Egberts, ASML Holding and the Atlantic Association) and serves on several state commissions and councils on behalf of the government (Advisory Council for Foreign Affairs) and as an diplomat and lobbyist for several economic delegations on behalf of the government and as an advocate for European integration.