Seymour Hersh has been the premier American investigative reporter of the last half-century. In the late 1960s his articles helped inspire a partly successful campaign to abolish America’s arsenal of chemical and biological weapons. His 1969 exposé of the My Lai massacre revealed the savagery of the Vietnam War. He provided the first comprehensive account of President Richard Nixon’s secret bombing of Cambodia. His disclosure in 1974 that the CIA had spied on antiwar activists prompted the creation of two congressional investigating committees. He led the effort to unearth American dirty tricks in the early 1970s against Chile’s democratic socialist president, Salvador Allende. After September 11, he warned that US intelligence was being manipulated to justify an invasion of Iraq, and in 2004 he brought to light the abuses at the Abu Ghraib prison. Hersh has also been dogged by criticism, some of it legitimate. He has bullied sources, lashed out at colleagues, succumbed to hoaxes, and destroyed the reputation of at least one blameless person.