The mass arrests of Aktion Gitter were neither unprecedented nor a spontaneous government response to the assassination attempt of July 1944, but the working through of long-standing policies. Leading politicians from the Weimar years had been identified on a so-called government "A-list" as early as 1935/36, divided into sub-categories A-1, A-2 and A-3. At the outbreak of the Second World War in 1939 the Gestapo had arrested between 2,000 and 4,000 people whose names appeared on List A-1. These were identified as "enemies of the state" and placed in "protective custody", in most cases in the Buchenwald concentration camp. However, most of these had been released by the summer of 1940. Nevertheless, Hitler gave notice in April 1942 that "if a mutiny were to break out today somewhere in the country", it would meet with an immediate response ("Sofortmaßnahmen"). Directly following the outbreak of civil arrest or similar disturbances, all leading men from the [left-wing] opposition, and indeed also those from the Catholic political tradition would be arrested, removed from their homes and sent for execution. Additionally all concentration camp inmates would be shot along with all criminals, whether they were in state detention or at liberty at the time.