Born Sept. 1, 1927, in Muskegon, Mich., Dunning spent most of his childhood in Gettysburg, Pa. He attended Mercersburg Academy, served in the Navy near the end of World War II, and after graduating from Princeton, earned master’s and Ph.D. degrees at Yale.
Between Princeton and Yale he was a National Park ranger on Mt. Rainier. He and his wife, Mary, were married for 61 years and raised two sons.
Dunning was on staff at the CIA from 1956 until retirement in 1986. There he supervised analyses of the Vietnam War and for a period, prepared the daily intelligence briefing for President Ronald Reagan.
A lifelong mountaineer, from his Princeton years until age 86, he climbed in the Tetons, Pike’s Peak, and Mt. Whitney. In Europe he climbed the Matterhorn and elsewhere in the Alps.
Since 1989 his family has lived in Colorado Springs, Colo. Dunning died June 8, 2018, at age 90. He is survived by Mary, sons Dunning V and Winthrop, a nephew, a niece, and three grandchildren.