The Lutheran Church in Germany divided into pro and anti-regime factions, with the anti-regime faction taking on the name of the "Confessing Church."

I can't speak much to specifics, but I can point you to Biographies of Karl Barth and Dietrich Bonhoeffer who were both prominent figures in the Confessing Church. To my mind Bonhoeffer is the more compelling figure. Barth fled to Switzerland and worked to support the Church in exile, but Bonhoeffer was imprisoned and Martyred. Both were prolific writers and are worth looking at.