What is The Abwehr?

The Abwehr was, for several years before and during World War II, a government secret service organization in Germany with a rivalry with the more violent, and the more friendly to Hitler, SS (short for "Schutzstaffel"). For several years, Bonhoeffer was a member of the Abwehr, essentially a double agent reporting the organization's activities back to his comrades in the conspiracy to kill Hitler and bring down the Nazi regime.