Born in Scranton on August 27, 1884, Duffy became Chief of the Electrical Department of the Delaware, Lackawanna and Western Railroad, and President of the Engineer's Society of Northeastern Pennsylvania.
He enlisted in the U.S. Army in 1917, was promoted to Lt. Col. on April 3, 1918 and commanded the 2nd Battalion, 103rd Engineers, which was part of the 28th Infantry. Dubbed the "Iron Division" by General John J. Pershing, Commander and Chief of the American Expeditionary Forces, the 28th Infantry occupied an area near Chateau-Thierry, France.
On August 17, 1918, Lt. Col. Duffy and his motorcycle driver, PFC Frank Fiore, also from Scranton, were killed by enemy mortar fire. Lt. Col. Duffy is the highest ranking officer from Lackawanna County killed in action during the Great War.
Duffy is buried near Chateau-Thierry at Oise-Aisne American Cemetery. His comrades proudly nicknamed him The Fighting Colonel. Indeed, it was widely remarked at the time of his death that Duffy's superior officers considered "the Fighting Colonel" worth 500 men!
The historical notes of the 28th Division state: "In his death the Division and Regiment lost a splendid soldier, an efficient officer and a man whose leadership had been an inspiration to the Command."