The Schutzstaffel (SS, "Protection Squad") is created out of Adolf Hitler's personal bodyguard. The SS is originally a branch of the SA (Sturmabteilung, "Brownshirts" or Stormtroopers), but the SA is somewhat independent of Hitler and thus perceived as a potential threat.
The SS is created to have an armed paramilitary organization that is personally loyal to Adolf Hitler and no one else.
By the end of World War II, the SS will have almost a million members, many in military units fighting in the field. The SS will be responsible for the vast majority of the war crimes committed under the Nazi regime, including most of what happens during the Holocaust.