Bonhoeffer's promising academic and ecclesiastical career was dramatically altered with the Nazi ascension to power on 30 January 1933. He was a determined opponent of the regime from its first days. Two days after Hitler was installed as Chancellor, Bonhoeffer delivered a radio address in which he attacked Hitler and warned Germany against slipping into an idolatrous cult of the Führer (leader), who could very well turn out to be Verführer (misleader, or seducer). He was cut off the air in the middle of a sentence, though it is unclear whether the newly elected Nazi regime was responsible. In April 1933, Bonhoeffer raised the first voice for church resistance to Hitler's persecution of Jews, declaring that the church must not simply "bandage the victims under the wheel, but jam a spoke in the wheel itself."
In opposition to Nazification, Bonhoeffer urged an interdict upon all pastoral services (baptisms, weddings, funerals, etc.), but Karl Barth and others advised against such a radical proposal. In August 1933, Bonhoeffer and Hermann Sasse were deputized by opposition church leaders to draft the Bethel Confession, a new statement of faith in opposition to the Deutsche Christen movement. Notable for affirming God's fidelity to Jews as His chosen people, the Bethel Confession was so watered down to make it more palatable that Bonhoeffer ultimately refused to sign it.
In September 1933, the national church synod at Wittenberg voluntarily passed a resolution to apply the Aryan paragraph within the church, meaning that pastors and church officials of Jewish descent were to be removed from their posts. Regarding this as an affront to the principle of baptism, Martin Niemöller founded the Pfarrernotbund (Pastors' Emergency League). In November, a rally of 20,000 Deutsche Christens demanded the removal of the Old Testament from the Bible, which was seen by many as heresy, further swelling the ranks of the Emergency League.