Overview
Wag the dog is, as a political term, the act of creating a diversion from a damaging issue usually through military force. It stems from the generic use of the term to mean a small and seemingly unimportant entity (the tail) controls a bigger, more important one (the dog). It is usually used by a politician when they are in a scandal, in hopes that people forget about the scandal and focus on the more important issue. The phrase originates in the saying "a dog is smarter than its tail, but if the tail were smarter, then it would wag the dog." The concept has strong intersections with many other aspects of Diversionary foreign policy, particularly the Rally 'round the flag effect, as wag the dog actions tend to both distract and seek to bolster support through these actions.
First usage
The earliest usage of the phrase in politics found in print is in an article originating in 1871, discussing one Democratic convention. In the article, the author references the popular play Our American Cousin, which Abraham Lincoln was watching six years earlier when he was assassinated by actor John Wilkes Booth. In the play, the character Lord Dundreary is a sympathetic character who constantly utters confused catch phrases a-la Yogi Berra, which were known at that time as Dundrearyisms:
The generic phrase, then and now, indicates a backwards situation in which a small and seemingly unimportant entity (the tail) controls a bigger, more important one (the dog). It was again used in the 1960s, as in the economic advice "don't let the tax tail wag the investment dog".
From Wikipedia (CC BY-SA 4.0).