Immediately following the collapse of the Nazi dictatorship at the end of World War II, the need for a new political order in Germany was paramount. Simultaneous yet unrelated meetings began occurring throughout Germany, each with the intention of planning a "Christian-democratic party". The "Christlich-Demokratische Union" was established in Berlin on 26 June 1945, and in Rheinland and Westfalen in September of the same year.
The founding members of the CDU consisted primarily of former members of the Centre Party, German Democratic Party, German National People's Party, and German People's Party. Many of these individuals, including CDU-Berlin founder Andreas Hermes and future chancellor of Germany Konrad Adenauer, were imprisoned for the involvement in the German Resistance during the Nazi dictatorship. In the Cold War years, after World War II up to the 1960s, the CDU also attracted conservative, anti-Communist former Nazis and Nazi collaborators into its higher ranks (like Hans Globke and Theodor Oberländer). A prominent anti-Nazi member was theologian Eugen Gerstenmaier who became Acting Chairman of the Foreign Board (1949-1969).
One of the lessons learned from the failure of the Weimar Republic was that disunity among the democratic parties ultimately allowed for the rise of the Nazi Party. It was therefore crucial to create a unified party of Christian Democrats – a Christian Democratic "Union". The result of these meetings was the establishment of an inter-confessional (Catholic and Protestant alike) party influenced heavily by the political tradition of liberal conservatism. The CDU experienced considerable success gaining support from the time of its creation in Berlin on 26 June 1945 until its first convention on 21 October 1950, at which Chancellor Adenauer was named the first Chairman of the party.
In the beginning, it was not clear which party would be favored by the victors of the Second World War, but by the end of the 1940s, the governments of the United States and of Britain began to lean toward the CDU and away from the Social Democratic Party of Germany (SPD). The latter was more nationalist and sought German reunification, even at the expense of concessions to the Soviet Union, depicting Adenauer as an instrument of both the Americans and the Vatican. The Western powers appreciated the CDU's moderation, its economic flexibility and its value as an oppositional force to the Communists, which appealed to European voters at the time. Also, Adenauer was trusted by the British.
The party was split over issues of rearmament within the Western alliance and German unification as a neutral state. Adenauer staunchly defended his pro-Western position and outmanoeuvred some of his opponents. He also refused to consider the SPD as a party of the coalition until he felt sure that they shared his anti-Communist position. The principled rejection of a reunification that would alienate Germany from the Western alliance made it harder to attract Protestant voters to the party, as most refugees from the former German territories east of the Oder were of that faith, as were the majority of the inhabitants of East Germany.
The CDU was the dominant party for the first two decades following the establishment of West Germany in 1949. Konrad Adenauer remained the party’s leader until 1963, at which point the former minister of economics Ludwig Erhard replaced him. As the Free Democratic Party (FDP) withdrew from the governing coalition in 1966 due to disagreements over fiscal and economic policy, Erhard was forced to resign. Consequently, a grand coalition with the SPD took over government under CDU Chancellor Kurt Georg Kiesinger.