McGuire then earned a scholarship to Yale University, where he worked at the Forest Service research facility on the campus while pursuing his M.F., awarded in 1941.

[1] During World War II, McGuire served with the United States Army in the Pacific, rising to the rank of major and commanding officer of the Eighth Engineers, which was part of the first American forces to occupy Manila and Tokyo.

[3] During his tenure as chief the service modified and integrated its methods of land management and weathered the attacks of some environmental critics.

McGuire worked to balance the needs of the lumber industry, the concerns of environmentalists and average citizens who might be shocked by the aesthetic result of the cutting.

He also served as Chairman of the U.S. delegation to the Eighth World Forestry Congress in Indonesia, and was a member of the Boone and Crockett Club.