Answer
Bonhoeffer was imprisoned at Tegel Prison for one and a half years. He was first arrested in April 1943, and was held in solitary confinement for most of his time there. During his imprisonment, Bonhoeffer continued to write and work on theological projects. He also engaged in correspondence with other prisoners and with his family. Bonhoeffer was executed in April 1945, shortly before the end of World War II.