When military authorities were in complete control, they
applied martial law firmly but reasonably. Captured opponents
to their regime were tried as spies. Sometimes they were executed
by firing-squads; more often they were imprisoned. The hostage
system - the custom of punishing the innocent when the guilty
parties could not be found -did much to further tarnish then
image. But the military governments were mild compared with
the SS, which gradually infiltrated everywhere. 8 Once the invasion
of Soviet Russia was under way, the Wehrmacht was
forced to hand over the SS responsibility for 'keeping order'
behind the front lines.
In December 1941, Field-Marshal Keitel issued an enabling
decree entitled 'Night and Fog', which authorized the SS to assume
arbitrary powers. From that date, summary executions of
communists, Jews and real or imagined enemies multiplied.
The SS also carried out group massacres, razings of whole
villages, pitiless deportations of populations.
Their systematic reign of terror was introduced into western
Europe in 1943. Persons suspected of committing acts of violence
against the occupying forces were tortured.