Stanley Karnow, a journalist most famous for covering the entirety of the Vietnam War, has died at the age of 87.

According to an Associated Press report, Karnow died in his sleep on January 27 at his home in Potomac, Maryland. Karnow died of congestive heart failure.

Karnow served in the U.S. Army Air Forces during World War II before beginning his career as a reporter. He soon after began reporting for Time, and briefly served as the magazine’s North African Bureau chief. Starting in 1959, Karnow became Time‘s Asia correspondent. He was present during the first American deaths in Vietnam that year.

Karnow covered the war until its end in 1974. His reports were eventually used to write his most famous book, Vietnam: A History. In addition to that definitive take on the Vietnam conflict, Karnow authored several other books such as In Our Image: America’s Empire in the Philippines and Mao and China: From Revolution to Revolution.

As recently as the year 2000, Karnow wrote a piece on the Vietnam War for Salon, calling the war ” a tragedy of epic dimensions for the United States as well as for Vietnam, where at least 3 million people, both soldiers and civilians, lost their lives.” Karnow was writing against modern arguments that sought to portray the Vietnam conflict as just and winnable.