In 1936, Klaus married Ernestine Seywald (2 April 1914 – 1 January 2001).[3] During World War II he served in the German Wehrmacht, temporarily as a staff member for General Heinz Guderian, as well as in campaigns in Poland, France, Finland and Russia. He was captured in early 1945 and held in a POW camp. After the war he worked as a lawyer in Hallein; in 1948 he became chairman of the regional ÖVP section Hallein District and pursued his political career.
Klaus was elected governor of the Austrian state of Salzburg in 1949. Re-elected twice in 1954 and 1959, he rose to a leading member of the ÖVP. When his party colleague, Chancellor Julius Raab, finally resigned in 1961, Klaus' influence as a representative of the "young reformers" grew. He became Minister of Finance under Raab's successor Alfons Gorbach, whom he succeeded as ÖVP party chairman on 20 September 1963. When Gorbach resigned on 25 February 1964, Klaus also followed him as Chancellor.
In office from 2 April 1964, Klaus initially continued the grand coalition with the Socialists under Vice-Chancellor Bruno Pittermann according to the Proporz system that had governed Austria since 1945. He led the ÖVP into the 1966 legislative election, during which he called for an end to the coalition. At that election, the ÖVP won a three-seat majority, theoretically leaving Klaus free to break off the coalition. However, reversing himself, Klaus proposed new coalition terms to Pittermann's successor as Socialist leader, Bruno Kreisky. Talks broke down when the Socialist rank and file balked at the proposed terms. [4] Klaus then formed an exclusively ÖVP cabinet, the first one-party government of the Second Republic.[5] In June first steps were agreed on joining the European Economic Community which in the long run finally led to Austria joining the European Union in 1995.
Klaus started many reforms and is remembered for his effective stewardship of the government, but he lost the 1970 election to Kreisky's Socialists. Klaus might have been able to continue by entering into a coalition with the Freedom Party of Austria (FPÖ), but immediately resigned after losing the elections.
Despite his "hard image", Klaus was celebrated at his 90th birthday all over the country. In September 1971 he published his memoirs "Macht und Ohnmacht in Österreich", and up to 1995 he frequently led seminars on political and social themes.
