Originally posted by MadScot
Almost every coup ever launched has been with the stated intention of 'restoring the consititution', 'protecting the state', 'national honour' or similar. In many cases the men undertaking the coup may well genuinely believe that they are acting in the national interest.
An it's certainly not the sort of thing that has never been planned for. Ignoring the near revolt of the officers over pay near the end of the Revolution, consider this:
Between the two World Wars, the US armed services used a country colour code for planning military operations, hence the 'Plan Orange' for war against Japan.
Interestingly there were two colours used for the United States itself - blue, as a belligerent, and white, for 'domestic disorders'.
Therefore plans certainly did exist for the use of the military to intervene in domestic events. Scenarios included overturning communistic or fascist political takeovers.