Palpatine has just crushed the Jedi, ended the Clone Wars, and declared himself Emperor. We see him standing on the bridge of a Star Destroyer, apparently conversing with Governor Tarkin, when Vader approaches and Tarkin is dismissed by the Emperor.

We know that by the time of the Battle of Yavin(ANH), Tarkin had been awarded the title of Grand Moff. He was given the title because of his unwavering service to Palpatine. He was given the position because he was probably the only governor that the Empire could trust to carry out the heinous policies of the Empire. Ironically enough, it was Tarkin himself that drafted the cornerstone policies that created the laws under which the galaxy would be brought into order. And that brings us to the Tarkin Doctrine, which was given to Palpatine sometime relatively soon after the events of Episode 3 passed.

Imperial Communique #0010044.92v: The Tarkin Doctrine

- Establish "Oversectors" to monitor and react to rebellious activities within tumultuous systems. Oversectors will receive more forces than other regions of the Empire, and this Imperial presence is designed to stop small Rebel factions before they become a larger threat.

- Assign command of each Oversector to a single individual who reports directly to the Emperor.

- Improve communication resources and Imperial response time by placing modified Holonet Transceivers aboard each flagship of every Sector Group within an Oversector command. Similar facilities have also been established aboard the Emperor's flagship and on Coruscant.

- Control unruly portions of the Galaxy through a fear of force, rather than actual force itself. Possibly the most integral aspect of the Tarkin Doctrine, this measure encourages the Empire to display its power and weaponry through potent symbols such as the Star Destroyer.

- Continue to research and develop new and more powerful starships and weapons designed to inspire fear in resistant systems.