Mark Mazetti’s The Way of the Knife: The CIA, a Secret Army, and a War at the Ends of the Earth explains that Obama’s expansion of drone war is linked with his opposition to black sites and Bushian enhanced interrogation. The TNR reviewer writes:

“To John Rizzo, the carryover general counsel at the CIA, the new administration chose targeted killing because that was ‘all that was left’ once it eliminated the interrogation option. Mazzetti puts the point in political terms. The’political conditions were set for an escalation of the secret wars,’ he maintains, because interrogation and detention were so controversial, and because no prominent Democrat had opposed drone strikes and the Republicans wouldn’t oppose Obama ‘for fighting too aggressive a campaign against terrorists.’ And so Barack Obama greatly expanded the secret war that George W. Bush began.”