Surprise is an event that occurs in the mind of an enemy commander
Someone came by today looking for the quote, "surprise is an event that occurs in the mind of an enemy commander." It wasn't anywhere on this site, but I came across this quote in Jerry Pournelle's Prince of Mercenaries, pg 299 in the Baen Books paperback edition.
It was one of Colonel Falkenberg's maxims, but it clearly not original to him. Unfortunately I do not know where it might be from.