His first major publication, The Warriors: Reflections on Men in Battle, is a philosophical memoir of his years as a counter-intelligence officer near the battle lines in Italy during World War II inspired by Gray’s opposition to war.
Immediately after this, Gray spent four years in the United States Army, becoming a second lieutenant.
As a long-time professor at Colorado College, Gray obtained fellowships from the Ford Foundation, John Simon Guggenheim Memorial Foundation, and the National Council on the Arts and Humanities.
As a general editor for Harper & Row, Gray supervised work for the publisher on translations of the German philosopher Martin Heidegger, with whom he formed a personal association, and was among his earliest champions in the United States.
Colleagues at Colorado College and elsewhere compiled a collection of essays, entitled Something of Great Constancy, in honor of Gray.