Operation Retrieve was the code name of a mission proposed by Starfleet Colonel Patrick West upon the arrest of Captain James T. Kirk and Doctor Leonard McCoy for the assassination of Chancellor Gorkon in 2293. It was devised, in light of increasing tensions between the United Federation of Planets and the Klingon Empire, to extricate the officers from their captivity by military force.
The details of the operation involved a direct incursion by several starships launched from Starbase 24 to the penal world of Rura Penthe, well within Klingon territory, and was expected to last no more than 24 hours with an acceptable loss to equipment and manpower. The Starfleet Marine Corps was also to have landed troops on Rura Penthe in a direct assault on the prison complex.
The plan was mooted by the Federation President and was subsequently proven to be unnecessary following the escape of Kirk and McCoy from their own imprisonment and the rescue of them by Kirk's own vessel, the USS Enterprise-A. (TOS movie: The Undiscovered Country)