If you know your history, you know that in 1934 there was an attempted coup in the United States that was thwarted largely due to the efforts of U.S. Marine Corps Major General Smedley Butler (ret.)
Look it up.
Among other things, Butler was only one of 19 people ever awarded the Medal of Honor twice and the only person to be awarded a Marine Corps Brevet Medal and a Medal of Honor for two different actions.
After it dawned on him how his heroism and the heroism of the troops under his command had been misused, he wrote a book called "War is a Racket" which I can virtually guarantee you never heard about in school.
Butler concluded there are only two reasons to ever take up arms:
1. To defend the country against real - not manufactured - attacks
2. To defend the Bill of Rights
Sounds good to me.