Mr. Obama has placed himself at the helm of a top secret nominations" process to designate terrorists for kill or capture, of which the capture part has become largely theoretical. Mr. Obama ... insisted on approving every new name on an expanding "kill list," poring over terrorist suspects' biographies. When a rare opportunity for a drone strike at a top terrorist arises -- but his family is with him -- it is the president who has reserved to himself the final moral calculation. In interviews with The New York Times, three dozen of his current and former advisers described Mr. Obama's evolution since taking on the role, without precedent in presidential history, of personally overseeing the shadow war. They describe a paradoxical leader who shunned the legislative deal-making required to close the detention facility at Guantnamo Bay in Cuba, but approves lethal action without hand-wringing. When he applies his lawyering skills to counterterrorism, it is usually to enable, not constrain, his ferocious campaign ... even when it comes to killing an American cleric in Yemen, a decision that Mr. Obama told colleagues was "an easy one." Beside the president at every step is his counterterrorism adviser, John O. Brennan, who is variously compared by colleagues to a dogged police detective, tracking terrorists from his cavelike office in the White House basement, or a priest whose blessing has become indispensable to Mr. Obama, echoing the president's attempt to apply the "just war" theories of Christian philosophers to a brutal modern conflict.