He joined the Gestapo and was sent to Paris in September 1940 where he headed its Jewish Bureau. Over the next two years he had the task of arranging for Jews in France to be deported to Auschwitz and other concentration camps in Eastern Europe.
In 1943 Dannecker was transferred to Bulgaria where he was ordered to implement the Final Solution. The following year he organized the rounding up of Jews in Italy and Hungary.
At the end of the Second World War Dannecker was arrested by Allied troops and committed suicide on 10th December 1945, while in an American prison camp.