I just received a book I ordered, Dietrich Bonhoeffer: Theological Education: 1937-1940. It is from a series, Dietrich Bonhoeffer Works, Vol. 15. The book, tome really, is filled with letters by Bonhoeffer to his Finkenwalde students after the seminaries were closed by the Gestapo. There are Bible study outlines, sermon notes, and so many letters as well as studies on such words as joy and temptation. And temptation is one of the important subjects in the letters written at the time. As the editor to the English Edition points out, the former students of Finkenwalde and other Confessing seminaries were deeply bothered by temptation.
The seminaries were developed by the Confessing Churches and their Councils of Brethren to help those called to ministry receive a proper education without being infected by the German Christians who at the time had taken over the official seminaries. But even at the beginning there were problems. The seminarians knew that they could not be ordained in the proper way. So they would have to rely on the Council of Brethren to ordain them and the Confessing Churches to use and pay them. And then the German Christians stepped in with the larger temptation. They would ordain them if they would come under the official consistories and take the exams given by the German Christians.
The temptation became greater when the Gestapo closed the Confessing Seminaries. Afterwards to be an unofficial pastor meant great risk. The first letter from Bonhoeffer that one reads to the former students mentions that four of them were in prison. Some of them stood strong. But not all.