Leipzig  ( subcamp of Buchenwald ),  Mülsen  ( subcamp of Flossenbürg ),  Flossenbürg , and  Regensburg  (subcamp of Flossenbürg). In Mülsen, on May 1, 1944,  Soviet  prisoners staged an uprising and mass escape attempt from the camp, which was located in the cellars of an arms factory. They set their bunks