Wikipedia
During World War II, the Nazi German were a sub-group of five mobile killing squads (term used by Holocaust historians) – up to 3,000 men total – usually composed of 500–1,000 functionaries of the SS and Gestapo, whose mission was to exterminate Jews, Polish intellectuals, Romani, Homosexuals, communists and the NKVD collaborators in the captured territories often far behind the advancing German front. After the outbreak of war with the Soviet Union known as Operation Barbarossa, the Red Army began to retreat so rapidly that the large Einsatzgruppen had to be split into dozens of smaller commandos (Einsatzkommandos), responsible for systematically killing Jews and, among others, alleged Soviet partisans behind the Wehrmacht lines. Several Einsatzkommando officers were tried, convicted of war crimes and hanged after the war (see Einsatzgruppen Trial).
As a military term, the German Einsatzkommando (Operational Command) is roughly equivalent to the English task force and is still in use for German paramilitary organizations, such as SEK and Einsatzkommando Cobra.