In the 1860s, New Brunswick experienced its own brand of international terrorism. The Fenian Brotherhood sought the ouster of the British from their beloved Ireland and found support among Irish-American immigrants. Eager to help the cause, the American Fenian sympathizers planned to invade British North America and hold it hostage. New Brunswick, with its large Irish population and undefended frontier, seemed the perfect target.

In the spring of 1866, a thousand Fenians massed along the southwest border of New Brunswick. But when Lieutenant-Governor Arthur Hamilton Gordon revitalized the New Brunswick militia, calling in British soldiers and a squadron of warships, the force proved too much for the enemy, who retreated and turned their efforts against the more vulnerable central Canada. The threat of this Fenian attack fanned the flames of an already red-hot political debate, and a year later, in 1867, New Brunswick joined Confederation.