Longest war in which only one shot was fired?

This is a fun trivia historical question  Don't read the answer until you've ponder the question a few moments.

QUESTION:  What was the longest war in U.S. history in which only one shot was fired?



ANSWER:  Lyman Cutlar, an American settler on San Juan Island between Bellingham, Washington, and Vancouver, in 1846 found a large black pig rooting in his garden and shot it.  The pig's owner, Charles Griffin, a Canadian demanded $100 in damages.  Cutlar offer $10.  Cutlar claimed "it was eating my potatoes."  Griffin rejoined, "It is up to you to keep your potatoes out of my pig."  Threatened with arrest by British authorities, the Americans called for military protection.  It turns out there was controversy over which country owned the land.  The Americans and British sent troops and ships, and there was a stand-off that lasted over a dozen years before the border dispute was settled.  Fortunately, no shots were fired, except the one that killed the pig.  It is called the Pig War.