Mark Twain (2014). “Mark Twain on Common Sense: Timeless Advice and Words of Wisdom from America's Most-Revered Humorist”, p.53, Skyhorse Publishing, Inc.
Attributed in Patton (motion picture) (1970). This is sometimes said to have been uttered in a speech by Patton to the Sixth Armored Division of the Third Army, 31 May 1944, but documentation is lacking. The following poem appeared in the Bureau of Aeronautics Navy Department News Letter, 1 Jan. 1943: "The greatest duty of a sailor / Is duty from worries and cares, / Not to die for his country, / Make our enemies die for theirs!"