Within the CDU he became a major rival of Konrad Adenauer , the party leader .
In 1948 Kaiser was forced to leave East Berlin and he went to West Berlin where he joined the West German Christian Democratic Union ( CDU ) .
Within the CDU Kaiser became a major rival of Konrad Adenauer , the party leader .
In 1948 Kaiser was forced to leave East Berlin and he went to West Berlin where he joined the West German Christian Democratic Union ( CDU ) .