Because of Kiesinger's involvement in the Nazi Party, the Allies interned him for eighteen months after the German surrender in 1945. In 1947, however, he was allowed to establish himself as a solicitor in Tübingen, where he joined the Christian Democratic Union (CDU). He was elected to the Bundestag in 1949 and was one of the earliest supporters of European integration, subsequently driving the integration of West Germany into the Western alliance. During 1958–1966, he served as minister president of Baden-Württemberg.
On 1 December 1966 Kiesinger succeeded Ludwig Erhard as chancellor, forming a coalition of West Germany's major parties. As chancellor, he committed himself to restructuring the federal budget and proposed a draft for a national emergency law, aimed at improving national security, that was passed by the Bundestag in 1968. His strong support of this hotly debated law was certainly a reaction to the student protests of 1967–1968 and the so-called extraparliamentary opposition, which he regarded as a threat to the state. It was also a clear sign of his conservatism. In foreign affairs, Kiesinger and foreign minister Willy Brandt took the lead in applying the Hallstein Doctrine with more flexibility.
Despite opposition from some hard-liners inside his own cabinet, Kiesinger followed Brandt's policy prescriptions. This was most clearly indicated in Kiesinger's Bundestag speech of 12 April 1967, when the chancellor addressed delegates of the Socialist Unity Party (SED) congress, an unthinkable action for his predecessors Konrad Adenauer or Erhard, who had never mentioned the German Democratic Republic (GDR, East Germany) so directly in an official speech. When Brandt became chancellor in October 1969, Kiesinger became CDU opposition leader until 1971. He remained in the Bundestag until 1980. Kiesinger died in Tübingen, Germany, on 9 March 1988.
Nicholls, Anthony James. The Bonn Republic: West German Democracy, 1945–1990. London and New York: Longman, 1997.; O'Dochartaigh, Pól. Germany since 1945. Houndsmill, UK, and New York: Palgrave Macmillan, 2004.