In 1866, one of the strangest armies in American history marched off to war. Made up of Irish-born Union and Confederate veterans who had only just finished fighting each other in the Civil War, this unlikely brigade was now united with one goal in mind – to break the British stranglehold over their native Ireland.
To realize their dream, the leaders of this underground society, known as the Fenian Brotherhood, planned to unleash their legion of Irish expats on Canada – the nearest British territory. With the colony under their control, the Brotherhood would use the territory above the 49th parallel as a bargaining chip in negotiations to free their homeland from the yoke of imperialist oppression.
On paper, the Fenian Brotherhood’s scheme looked feasible enough. It could draw from up to 17,000 combat hardened Irishmen. It had stockpiled surplus arms and equipment from the Civil War. The Fenians also enjoyed financial backing from scores of Irish Americans. It had a provisional government waiting in New York. It could even count on tacit support from a U.S. government still burning with resentment over Britain’s sympathy for the southern rebellion. To the Brotherhood, the campaign to seize Canada seemed entirely plausible. Yet, things didn’t wok out that way.
While its soldiers were combat veterans from both the northern states and the south, the Fenian Brotherhood was actually formed before the Civil War even broke out. An offshoot of the United Irishmen, a movement that launched an anti-British insurgency in Ireland in the 1790s, the Fenian cause was brought into America with Irish immigrants throughout first half of the 19th Century.
As war between the states loomed, the Brotherhood saw the coming conflict as an opportunity for Irish Americans to learn how to fight, a skill they hoped members would someday put to good use against the British Empire. Prominent Irish Americans like John O’Mahony and William Roberts raised regiments of fellow expats in New York, Chicago and Philadelphia, while their compatriots in the southern states like Father John Bannon helped form groups of Irish volunteers throughout the Confederacy. 
While northern and southern Irish units on occasion faced each other in combat during the four years of the Civil War, often the opposing regiments would arrange “soldiers truces” when they could. Senior commanders tolerated the gatherings believing them impromptu get-togethers between kinsmen – in reality, the meetings enabled the Fenians to organize. 
With the war over, the Fenians decided that the time to act was at hand. The Brotherhood’s leadership met in the latter half of 1865 to plan their invasion of Canada and put out the call to members to assemble. One of their marshalling points was Buffalo, New York. Another was Maine. Brotherhood officials even met with U.S. president Andrew Johnson who indicated that Washington would not interfere and would even recognize the Fenian cause if it managed to secure Canada.  By the spring of 1866, thousands of vets from both Union and Confederate armies had gathered, arms and ammunition were distributed, officers were appointed and final plans of attack were drawn up.
In April, the Fenians made their first foray onto Canadian soil. A detachment of 1,000 vets marshaled in Maine seized Campobello Island, which was part of the British colony of New Brunswick.
An even larger operation took place a few weeks later on the Great Lakes.
On June 1, a battalion of nearly 1,300 Fenians under the command of Col. John O’Neill, the former commander of the 5th Indiana Cavalry, crossed the mouth of the Niagara River at Buffalo, NY.  The group of Irish soldiers who hailed from such states as New York, Ohio, Tennessee, Louisiana and Kentucky, captured the Canadian border town of Fort Erie with minimal resistance.  The plan was to establish a foothold in Canada on Lake Erie, swiftly move on to Toronto, and then push east towards Montreal and Quebec City.
Surprised, the Canadian authorities quickly slapped together a force of nearly 1,000 militia and some regulars and rushed them to meet the Fenians. Recognizing that their men would soon be facing an army of battle hardened Civil War vets, the commanders issued their green troops with a brand new consignment of Spencer repeating rifles. The commanders hopes the added firepower would make up for their men’s lack of experience. Unfortunately, few of the novice defenders had ever handled the weapons before, let alone fired them. 
Learning that British and Canadian troops were moving towards him, O’Neill left a small force to hold Fort Erie and set off to intercept the enemy. The two armies met outside the village of Ridgeway, Ontario on the morning of June 2.
The 90 minute engagement saw a force of Canadians push the Fenians back, but when a handful of Irish mounted scouts appeared, the redcoats mistakenly took them for the vanguard of a larger cavalry force. The defenders quickly formed squares and in the confusion left themselves open to a Fenian bayonet charge.  The British and Canadians were pushed from the field, leaving seven dead. More than 60 were wounded, 20 of those would die later. For their part, the Fenians lost six men and suffered 10 wounded.
The Invasion Fizzles
Despite the victory at Ridgway, O’Neill realized his foothold in Canada was growing more tenuous by the hour. Scores of British and Canadian reinforcements were converging on the Niagara region as the day wore on. But worst of all, the American government, which had previously maintained a policy of benign indifference to the Fenians, had suddenly grown wary of provoking a war with Britain. Following the initial landings at Fort Erie, an American warship, the USS Michigan, had taken up a station off Buffalo and turned away Fenian reinforcements who had planned to cross into Canada. Meanwhile military authorities in New York State under the command of no less than Gen. Ulysses Grant and Gen. George Meade had converged on Buffalo to disarm and arrest the Fenians gathered there. Realizing his forces were alone in Canada and cut off from fresh troops and supplies, O’Neill beat a hasty retreat to the stronghold of Fort Erie, not before clashing again with a force of fewer than 80 fresh Canadian militia. Despite capturing more than 50 militiamen at Fort Erie, the Fenians recognized that the tide had turned against them fled across the border into the waiting arms of the U.S. authorities.
The End of the Dream
Within days of their failed gambit on the Great Lakes, the Fenians would send more insurgents into New Brunswick on the Atlantic Coast, only to be handily pushed back by Canadian forces and again intercepted by the U.S. military.
With Washington turning on the Fenians, scattering its members and seizing its weapons at every turn, the movement was hard pressed to organize another invasion on the scale in could muster in 1866.
Other smaller forays would be planned and mounted into Quebec and into the Canadian prairies in 1870 and 1871 respectively, but these were quickly dispersed by both American and Canadian authorities.
With its numbers dwindling and its Civil War vets moving on into civilian life, the Brotherhood’s schemes became even more desperate and outlandish.
In 1881, the movement financed a 30-foot long submarine it dubbed The Fenian Ram, ostensibly to be used against British shipping. Unable to find a crew to operate it, the sub was mothballed in 1883, only to be pulled from storage in 1916 for use as a public attraction at Irish Republican fundraisers in the United States. 
Ironically, while the Fenians sought to break the British stranglehold over Ireland, the only country to gain independence as a result of its 1866 raids was Canada. The attacks, which were largely repelled by local militia, generated a new surge on patriotic fervor in Canada that would be a factor in the colonies’ amicable independence from Great Britain in 1867.
However, Ireland would finally achieve independence from Great Britain in 1922 following its own war of independence between 1919 and 1921.
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