Taken to Tegel Prison, Bonhoeffer began what would ultimately be the most prolific part of his life.
Already a respected author, The Cost of Discipleship became an apt title for his new life as a prisoner of the Third Reich. The central theme of that 1939 book - true Christians must do all they can to follow Christ - must have resonated through Bonhoeffer as he lived his life in Cell 92.
By July 1944, many high-ranking government officials had long been convinced that Hitler and his cohorts were leading Germany down a path of ultimate destruction. Even though economic conditions in Germany had improved under Hitler's regime, his opponents could see the future with Hitler. It was a terrible vision.
Germans were upset with the way the victors of World War I had dealt with their country at the end of the war. The Nazis capitalized on this smoldering resentment. The Treaty of Versailles (ending WWI) had required Germany to give up some of its territories. Germans wanted that land back.
Hitler saw an opportunity. By playing into the fears of the German people, Hitler had used his considerable oratory skills to convince many individuals that he and his party were the best thing for the country. But some of the military commanders who originally thought Hitler could help Germany realized he had to go.
The only way to get rid of him - in the minds of many high-ranking people - was to assassinate him.
Members of Bonhoeffer's resistance group and German officers with access to Hitler - like Colonel Claus von Stauffenberg - took part in the plot to assassinate the Fuhrer. The plan had been years in the making.
The plot came to fruition while Bonhoeffer was already in prison for smuggling Jews out of the country. On July 20, 1944, Colonel von Stauffenberg left a briefcase bomb in Hitler's heavily fortified planning room at Wolf's Lair (in East Prussia, now Poland). The bomb exploded but Hitler, shaken, survived the attempt.
The Nazis shot Von Stauffenberg the same evening in Berlin.
Two days after the assassination attempt, the Nazi Party's newspaper demanded that Germans make even-greater sacrifices and give absolute obedience to the party and to government leaders. Officials in charge of trials, orchestrated to condemn the plot's leaders, had one object in mind: demonstrate their own loyalty to Hitler.
Rules required for just trials were completely ignored.
The Nazis implicated thousands of people in the assassination plot, including Bonhoeffer and three members of his immediate family (his brother Klaus and two brothers-in-law). The Gestapo had found Incriminating documents, hidden by his sister's husband Hans von Dohnanyi.
Although he did not-yet realize the secret papers were in the hands of his enemies, Bonhoeffer was a condemned man.
Transferred to the Berlin Gestapo Prison in February 1945, Bonhoeffer knew he would be executed. His correspondence from prison - smuggled out and published as Letters and Papers From Prison - reflect the knowledge of his impending death. Few martyrs have so vividly painted a picture of events leading to their final act of courage.
But prison was not the end for Dietrich Bonhoeffer. The Gestapo had other, more brutal plans in store for him.
He was transferred to Buchenwald, the infamous concentration camp.