Jürgen Stroop, the Nazi commander who led the killing of more than 50,000 Jews, was sitting in a cell in Warsaw awaiting his own execution. Before he met the gallows, Stroop described in unrepentant detail his ascent as a Nazi, his destruction of the Warsaw Ghetto and his daily prosecution of mass murder. He gave his account to Kazimierz Moczarski, the journalist, Polish resistance leader and veteran of the Warsaw Uprising who shared Stroop’s c…