Ralph Waldo Emerson (2010). “Essays and English Traits by Ralph Waldo Emerson: The Five Foot Shelf of Classics, Vol. V (in 51 Volumes)”, p.296, Cosimo, Inc.
The People, Yes pt. 23 (1936). The popular form of this expression was crystallized when Charlotte Keyes published an article titled "Suppose They Gave a War and No One Came?" in McCall's, Oct. 1966.