In “Hard Choices,” Clinton, a former secretary of state and former U.S. senator who is exploring a 2016 presidential campaign, writes: “[M]any Senators came to wish they had voted against the resolution. I was one of them. As the war dragged on, with every letter I sent to a family in New York who had lost a son or daughter, a father or mother, my mistake become (sic) more painful.”

Clinton continues, “I thought I had acted in good faith and made the best decision I could with the information I had. And I wasn’t alone in getting it wrong. But I still got it wrong. Plain and simple.”