David H. Petraeus, the best-known military commander of his generation, has reached a plea deal with the Justice Department and admitted providing his highly classified journals to a mistress when he was the director of the C.I.A. Mr. Petraeus has agreed to plead guilty to one count of unauthorized removal and retention of classified material, a misdemeanor. He is eligible for up to one year in prison but prosecutors will recommend a sentence of probation for two years and a $40,000 fine. The plea deal completes a spectacular fall for Mr. Petraeus, a retired four-star general who was once discussed...