Koning was a Dutch novelist who played an active part in the anti-fascist resistance during World War II, and subsequently emmigrated to the USA. Author of several novels including The Revolutionary and De witt's War, he also wrote a "groundbreaking" book on Christopher Columbus: Columbus: His Enterprise: Exploding the Myth (1976) and a sequel The Conquest of America: How the Indian Nations Lost Their Continent (1993). He played an active part in opposition to the Vietnam War and was one of the founders of the anti-war group Resist.
There is a good overview of his life on InterActivist Info Exhange:
and an obituary in the New York Times: