"Operation Greif" . . "Operation Greif" . . . "use of American uniforms in infiltrating American lines" . . . . "disguised as Americans" . . . "disguised themselves as Americans" . . . "German soldier who has infiltrated the American lines" . . . . . "German soldiers attempting to infiltrate American ranks" . . "Greif" . "are dropped behind American lines" . . "Operation Griffin" . . . . .