Fighting Father Duffy is a biography by Jim Bishop, first published in 1956 as part of the Vision Books series for young readers. It tells the life story of Francis P. Duffy, the legendary Catholic chaplain of the "Fighting 69th" (federalized as the 165th Infantry Regiment) during World War I. 

Synopsis

The book follows Duffy from his youth in Cobourg, Ontario, through his education and priesthood in New York, and culminates in his service with the famous Irish-American regiment on the Western Front.

It covers:

• His childhood and decision to become a Catholic priest.
• Service as a teacher and parish priest in New York.
• Appointment as chaplain to the 69th Infantry Regiment (New York), known as the "Fighting 69th."
• Training and deployment to France in 1917.
• His work celebrating Mass, counseling soldiers, and accompanying stretcher-bearers under fire.
• Major engagements including the Battle of the Ourcq, the Saint-Mihiel Offensive, and the Meuse–Argonne Offensive.
• His postwar ministry and enduring reputation among veterans