Born in Kötschach-Mauthen, Carinthia, the son of a master baker, Klaus attended the Catholicjunior seminary in Klagenfurt. He studied law at the University of Vienna, where he joined the Cartellverband of Catholic male student fraternities. He obtained his doctorate in 1934 and worked in the legal department of the Chamber of Labour which at that time was integrated into the Austrofascist unitary trade union centres by the government of the Federal State of Austria. When the Chamber organisation finally was liquidated after the 1938 Anschluss annexation by Nazi Germany, Klaus changed to the private sector. In 1936, Klaus married Ernestine Seywald. 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. After 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. In the 1966 legislative election, the ÖVP under Klaus won an absolute majority. Despite this, memories of the factionalism that had plagued the First Republic were still strong enough that Klaus initially tried to continue the grand coalition. However, when talks with Pittermann's successor as Socialist leader, Bruno Kreisky, failed, Klaus formed the first one-party government of the Second Republic. 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, 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.
