Maine and a British colony mobilised armies over a border, and never fought

In 1838–39, a dispute over the Maine–New Brunswick border saw both sides raise militias, build forts and ship in thousands of troops — yet the 'Aroostook War' produced no battles and no deaths beyond a handful of accidents. It was settled diplomatically by the Webster–Ashburton Treaty of 1842, which drew the border still used today.

— Standard accounts of the Maine–New Brunswick boundary dispute, Aroostook War — 1838–1839