William Beecher, who as a reporter for The New York Times revealed President Richard M. Nixon’s secret bombing campaign over Cambodia during the Vietnam War, and who later won a Pulitzer Prize at The Boston Globe, died on Feb. 9 at his home in Wilmington, N.C. He was 90. His daughter, Lori Beecher, and son-in-law, Marc Burstein, confirmed the death. President Nixon ordered the bombings, code-named Operation Menu, in March 1969 in response to stepped-up attacks by the North Vietnamese Army and South Vietnamese guerrillas based in Cambodia, a neutral country. The campaign was so secret that even William P....