Operation Valkyrie was the official code-name for an emergency contingency plan designed to protect the Nazi regime against the potential threat of serious internal disturbances or uprisings during World War II. The presence of millions of foreign workers, compelled to work as forced laborers, was the most likely reason for such concern on Hitler's part.
Valkyrie was the brainchild of General Friedrich Olbricht who served under Home Army Commander General Friedrich Fromm. What Hitler did not know was that Olbricht and later Home Army Chief of Staff Colonel Claus von Stauffenberg were secretly transforming Valkyrie into an elaborate coup d'etat plan to overthrow the Nazi regime.
Source: Joric Center