He served as an officer in the United States Air Force, reaching the rank of lieutenant colonel.

Edmondson played a key role in Bobby Fischer's path to the World Chess Champion in 1972.

He asked Pal Benko, who had qualified for the 1970 Interzonal, to yield his spot to Fischer.

[2] Benko realized that Fischer had a much greater chance of winning and agreed, receiving a fee of $2,000.

[3] Edmondson served as Fischer's manager during the 1970 Interzonal, and during his winning 1971 Candidates Tournament' matches against Mark Taimanov, Bent Larsen, and Tigran Petrosian.