's Commando Order (Kommandobefehl in German) that was secretly distributed to high command, ordering that all irregulars (ie. commandos) captured be handed over to the Sicherheitsdienst (SD: intelligence arm of the SS) for interrogation and execution.
Used in common speech as a reference to eradicating a group of (usually valiant) people.
It has recently surfaced in popular culture in the George Lucas
film Star Wars Episode III: Revenge of the Sith, when Emperor Palpatine orders his Stormtroopers to "execute order 66", which is the instruction to kill all Jedi.