SD(Sicherheitsdienst des Reichsfuehrers-SS), SS security and intelligence service. The SD played an important role in carrying out the Final Solution.
SD officers served in Einsatzgruppen, police and other security units. It was established in 1932 under Reinhard Heydrich and in 1938 incorporated into the Reichssicherheitshauptamt (Reich Security Main Office, RSHA).
Sources: Encyclopedia of the Holocaust; Historical Atlas of the Holocaust.