As a corollary, I'd like to add this as a rule:

If you are engaged in a mass bombing of civilians and military targets or committing ground forces to combative action for a period of longer than a week or two, that is a war, not a "police action" or other euphemism meant to get around (American) Constitutional requirements.

Yes. I posted to this thread https://news.ycombinator.com/item?id=2158522 outlining some of the unfortunate history of war and militarism changing the face of what was originally a more libertarian (small L) form of government in the U.S. If I were to expand that comment I would add the role Wilsonian Internationalism played in making War a good thing, if not a moral obligation. War becomes a euphemism for any given social engineering project (war on poverty, war on cancer, war on obesity, war on drugs).