Long Screwdriver Meaning

(idiomatic) Interference (usually in military matters) by politicians.

Example: 2009, Richard Holmes, Churchill's Bunker: The Cabinet War Rooms and the Culture of Secrecy in Wartime London, Yale University Press:
  The telegraph, telephone, and then radio made it easier for governments to intervene in the conduct of military operations, inserting that 'long screwdriver' so resented by modern commanders.