How can the compulsory element of power be united with love? Nobody felt the weight of this question more than Luther, who had to combine his highly spiritual ethics of love with his highly realistic politics of absolutistic power. Luther answered with the statement that compulsion is the strange work of love. Sweetness, self-surrender and mercy are, according to him, the proper work of love, bitterness, killing, and condemnation are its strange work, but both are works of love. What he meant could be expressed in the statement that it is the strange work of love to destroy what is against love. This, however, presupposes the unity of love and power. Love, in order to exercise its proper works, namely charity and forgiveness, must provide for a place on which this can be done, through its strange work of judging and punishing. In order to destroy what is against love, love must be united with power, and not only with power, but also with compulsory power….Love, through compulsory power, must destroy what is against love. But love cannot destroy him who acts against love. Even when destroying his work it does not destroy him. It tries to save and fulfill him by destroying in him what is against love.
–Paul Tillich, Love, Power, and Justice: Ontological Analyses and Ethical Applications, Oxford University Press, 1954