Barack Obama campaigned on a promise of change from George W. Bush's "global war on terror." Yet from indefinite detention and drone strikes to surveillance and military tribunals, Obama ended up continuing-and in some cases expanding-many policies he inherited. What happened?

In Power Wars, Charlie Savage looks inside the Obama administration's national security legal and policy team in a way that no one has before. Based on exclusive interviews with more than 150 current and former officials and access to previously unreported documents, he lays bare their internal deliberations, including emotional debates over the fates of detainees held on torture-tainted evidence and acts of war that lacked congressional authorization. He tells the inside stories of how Obama came to order the killing of an American citizen, preside over an unprecedented crackdown on leaks, and keep a then-secret National Security Agency program that collected records of every American's phone calls.

Savage also pieces together the first comprehensive history of how American surveillance secretly developed over the past thirty-five years, synthesizing recent revelations and filling in gaps with new reporting. And he provides lucid explanations of legal dilemmas in a way that non-lawyers can understand. Highlighted by new information about the pivotal aftermath to the failed Christmas underwear bombing and the planning for the Osama bin Laden raid, Savage's own eyewitness reporting at Guantánamo, and detailed accounts of closed-door meetings at the highest levels of government, Power Wars equips readers to understand the legacy of Obama's presidency.