Gary Cooper originally did not want to play a father of grown up children. This was despite the fact that he was 55 in real life. Ironically, many critics in 1956 felt he looked too old to play Jess Birdwell.
The official name of the Quaker religion is Society of Friends. Members of the faith are called Friends and nicknamed Quakers. The book is called "The Friendly Persuasion", meaning the faith. The film is simply called "Friendly Persuasion," which more specifically refers to the Quakers' way of communicating.
The battle depicted in the film, against the Confederate raiders led by General John Hunt Morgan, is based on an actual battle. On July 9, 1863, (actually a year later than the date mentioned in the film) 450 members of the Indiana Home Guard met John Hunt Morgan's raiders in battle south of the town of Corydon, Indiana (although not, as depicted in the film, at a creek crossing). The Home Guard held off the raiders for a half-hour, but the raiders numbered 2,400, and the Home Guard was eventually forced to retreat. The Morgan raiders occupied the town of Corydon for a single afternoon, during which time they looted stores in the town and forced several mill owners to pay cash ransoms in return for not burning their mills. At 5 o'clock, the raiders moved on. During the battle, the Morgan raiders suffered 11 men killed and 33 wounded, while the Indiana Home Guard lost only 5 men.