The Irish Republican Brotherhood (IRB) was established in 1858 in Ireland and the United States as a secular, revolutionary movement committed to armed struggle against Great Britain in order "to make Ireland an independent democratic republic" as members pledged when taking the society's oath. In 1859, the American wing—"equal, if not senior, partners in the trans-Atlantic organization," according to historian Hereward Senior—became known as the Fenian Brotherhood, a name derived from the Fianna, the militia of the warrior Fionn MacCumhail of Gaelic legend.

Modeled on earlier Irish revolutionary organizations by revolutionaries who had fled Ireland following the failed rising of 1848, the Fenian Brotherhood and the IRB emerged following a decade during which the population in Ireland had declined from 8.5 million to six million due to famine, disease, and mass migration, especially to the U.S. In a resolution agreed upon at the first Fenian Congress in the U.S., held in Chicago in November 1863, Fenians expressed "intense and undying hatred towards the monarchy and oligarchy of Great Britain" that, they charged, had "ground their country to the dust, hanging her patriots, starving out her people, and sweeping myriads of Irishmen, women, and children off their paternal fields, to find refuge in foreign lands."

Although the Fenian Brotherhood remained in existence until 1886, its most notable North American exploits, a series of failed military raids into Canada, occurred in 1866. After 1866, the IRB center of gravity moved to Ireland, although in 1870 Fenians undertook another series of raids into Canada. Following 1870, as the Fenian Brotherhood declined in importance, the group Clan na Gael developed into the most prominent Irish-American revolutionary organization, and during the second half of the 1870s, the latter group became allied with the IRB. Throughout this period, the words "Fenian" and "Fenianism" were applied to the IRB as a whole and to revolutionaries not connected with the original Fenian Brotherhood. Historians have noted significant unintended consequences in Canada of the Fenian raids and have contended that Fenianism influenced later Irish nationalist movements of the early 20th century.

In 1866, the Fenian Brotherhood conducted three military incursions into Canada after plans for an insurrection in Ireland had fallen apart due to British raids against the IRB in Dublin in September 1865 that had resulted in arrests and dispersal of the leadership. With many Irish-American veterans of the American Civil War in their ranks, the Fenians decided to seize territory in British North America and proclaim an Irish Republic. They hoped their raids would encourage the United States to follow with troops in order to establish the St. Lawrence River as its northern border or even to annex the whole of Canada.

During the Civil War, tensions had heightened between the U.S. and Great Britain when the latter, after declaring its neutrality in the conflict, allowed Confederate diplomats passage on British ships and sanctioned the building in England of Confederate cruisers that later destroyed Union merchant ships. American hostility to Great Britain increased in October 1864 when a Confederate band, after crossing the Canadian border, robbed banks in St. Albans, Vermont, stole horses, set fire to houses, and shot a citizen before returning to Canada. After a local Canadian court released the raiders on a technicality, voices in the American press called for an invasion.

The movement in 1865 in the U.S. for the annexation of Canada, characterized as ephemeral by historian Donald F. Warner, included calls in the press for Union and Confederate armies to unite to attack Canada and schemes of politicians to coerce annexation through economic pressure. Although expressions of U.S. interest in annexing Canada died down following the end of Civil War hostilities, the Fenians nevertheless hoped that their planned invasion would revive the annexation movement and draw British troops to North America leaving Ireland vulnerable.

The plan of attack, devised by the Fenian secretary of war who had been a U.S. Army major during the Civil War, called for multiple invasions: across the Vermont-Canadian border; from Malone and Potsdam in New York to the Canadian towns of Cornwall and Prescott, then north to Ottawa and Montreal; across Lake Michigan and Lake Huron to Stratford and London in order to gain control of an important railway terminal; and incursions to capture Toronto and major waterway and railway centers. The Fenians had some reason to believe that the U.S. government would recognize an Irish republic on captured British soil, as President Andrew Johnson and his Secretary of State, William Seward, anxious not to antagonize Irish-American voters, reportedly stated that the U.S. would "acknowledge accomplished facts," in the words of historian William D'Arcy, when they were informed by a Fenian delegation about the group's vague intentions to seize territory in Canada. No official U.S. commitment, however, ever was committed to writing.

Canadian historians have concluded that in addition to misreading the response of U.S. politicians, the Fenians also misjudged the Canadians. Their invasion plan was formulated, Hereward Senior has written, "without much regard for Canadian history or the contemporary political scene." W. S. Neidhardt has pointed out that Fenian plans to win over key elements of the Canadian populace "were based on completely false assumptions." Contrary to their beliefs, most Canadians of Irish descent were Protestants from Northern Ireland, not Catholics like the Fenians. Furthermore, for many Irish Catholics, "Canada offered a reasonably good government, a fair legal and adequate educational system, and an opportunity to maintain a decent standard of living." Most Canadians who had experienced the Famine in Ireland during the 1840s were unlikely to risk their present situation to support the Fenians' scheme.

The first Fenian operation of 1866 occurred in April when a small force raided Indian Island in New Brunswick as part of a plan to invade the nearby island of Campobello in order to establish a base for a later landing in Ireland, for launching cruisers to attack British commercial vessels, and as a diversionary tactic designed to keep British troops in North America preoccupied while revolutionaries in Ireland attempted a rising. By declaring themselves a republic at war with Great Britain, the Fenians hoped to attain the status of belligerents, rather than pirates, and thus not risk violating U.S. neutrality laws. A concerted effort by Canadian militias, well-armed British naval vessels, and the American military, however, confounded Fenian plans with only a few shots fired during confrontations and no reported casualties.

Some nine combatants from each side were killed in battle, however, during the second Fenian invasion of 1866, which began in the early morning of June 1 as a Fenian force of nearly 1,000 men traveling on canal boats that were towed by tugs crossed the Niagara River near Buffalo and landed at a dock just north of the Canadian village of Fort Erie, which they proceeded to occupy. Two days later, following a victory at Ridgeway over ill-prepared Canadian volunteer forces—the ease of disrupting the Campobello plot apparently had led to complacency among Canadian troops—the Fenians, aware that a large Canadian force was approaching, retreated back across the Niagara River, where U.S. naval forces belatedly called into action arrested them. Three days later, President Johnson issued a proclamation characterizing the Fenians as "evil-disposed persons" and their actions as "proceedings which constitute a high misdemeanor, forbidden by the laws of the United States as well as by the law of nations."

The final Fenian raid in 1866 took place one day after Johnson's proclamation, on June 7, when a band of less than 1,000 raiders starting out from St. Albans crossed the Vermont border and planted an Irish flag near the Canadian village of Pigeon Hill. Fenians subsequently occupied Pigeon Hill and three additional Canadian villages before fleeing from a Canadian cavalry corps that chased them back to the border. Under political pressure during a congressional election year, Johnson issued executive orders to release Fenians arrested in the raids and return arms that were seized, and intervened with British authorities to try to get Fenian prisoners in Canada and Ireland released. Although 25 of the invaders were tried and convicted, all but one—a man who died in prison—were pardoned by 1872.

After the congressional elections of 1866, the Fenians no longer were able to exert a significant influence over American politicians. Plagued by factional fighting, financial troubles, police informers, and opposition from the Catholic Church, they did not attempt another Canadian raid until May 24, 1870, a date chosen to coincide with Queen Victoria's birthday. On that day, President Ulysses S. Grant issued a proclamation warning U.S. citizens "against aiding, countenancing, abetting, or taking part" in reported "sundry illegal military enterprises and expeditions" aimed "against the people and district of the Dominion of Canada."

A Fenian force of less than 200 men crossed the border the next day despite warnings from a U.S. marshal that Canadian riflemen in well-chosen positions on an overlooking hill awaited their arrival. Although four or five Fenians died in the subsequent battle, as the Fenians fled, their commander, John O'Neill, berated them for cowardice. O'Neill himself then was arrested by the marshal. On the following day, a group of more than 450 Fenians gathered in Malone, New York and advanced over the border. In a skirmish with Canadian forces the next day, one Fenian was killed before most retreated to Malone. Despite entreaties by their general for further action, most of the Fenians remained convinced that they had no chance to win and the general was arrested. The Canadians suffered no serious casualties during the 1870 raids. In October 1871, O'Neill, having resigned from the Fenian Council, led a group of three dozen men across the Canadian border into Manitoba in an unsuccessful raid that an advocate for the independence of the Red River Colony had proposed, but which the Fenian Council had rejected. Historians have credited the Fenian raids with encouraging a nationalistic spirit in Canada and spurring the movement to confederacy.

Despite failure in North America, the Fenians, after shifting their focus of attention to Great Britain at the end of 1866, "helped to work a change in the traditional English attitude toward Ireland," according to historian Brian Jenkins. Locating themselves in London, Fenian leaders, supported financially by Irish-American contributions, adopted a strategy of guerrilla warfare. In a proclamation published in the Times of London in March 1867, they announced the formation of an Irish Republic and Provisional Government. During that month, Fenians fought police and soldiers in clashes throughout Ireland in an attempted rising. In November, three Fenians, executed on the basis of doubtful evidence for the murder of a police officer who had been escorting captured Fenian leaders to prison, were heralded in the press as the "Manchester Martyrs." In December, 12 Londoners were killed in an explosion designed to facilitate the escape from prison of a Fenian armaments organizer.

In response to fears of the British populace stimulated by the return of Irish revolutionary activity, the new Liberal Party Prime Minister, William Ewart Gladstone, in 1869 and 1870, successfully enacted laws to disestablish the Church of Ireland and address longstanding Irish land tenure issues. Gladstone acknowledged that Fenianism had "produced that attitude of attention and preparedness on the whole population of this country which qualified them to embrace, in a manner foreign to their habits in other times, the vast importance of the Irish controversy." Gladstone's actions, historian Oliver P. Rafferty has written, were intended "to alienate Fenian opinion, and enable the mass of the Irish people to differentiate their aspirations from those of the revolutionaries." Subsequently, the Irish Protestant barrister Isaac Butt advocated home rule for Ireland as an alternative to an Irish republic, stating that Fenianism "taught me the depth, the breadth, the sincerity of that love of fatherland that misgovernment had tortured into disaffection and . . . exaggerated into revolt." While a number of leading Fenians supported the home rule movement and entered into mainstream politics, under an agreement characterized as the "New Departure," Fenians also maintained their revolutionary commitment to create through insurrection an independent Irish republic.

Rafferty has contended that "the Fenian idea of the necessity, or inevitability, of armed insurrection passed into Irish historical lore and conditioned the thinking of, perhaps, the majority of those who staged the 1916 insurrection." In a recently published history of the rise of Irish nationalism during the period between the 1880s and the Easter rising of 1916, M. J. Kelly has asserted, "Historians have largely neglected the activities of the Irish Republican Brotherhood in the 1880s, tending to focus on the two great flash-points of 1867 and 1916." In his revisionist history, Kelly has looked anew at a "second generation of Fenians, qualitatively distinct from their fathers and uncles," who developed "a fresh separatist dynamic based on the nurture of a distinctly Irish culture" and significantly influenced subsequent Irish nationalist political activity and ideals.

Prior to the War of 1812, the Shawnee chief Tecumseh tried with his brother Tenskwatawa, a religious leader known as the Prophet, to revivify a confederacy of Indian peoples and rebuild it strong enough to halt the rapid expansion into their lands of American settlers, prevent additional lands from being sold to whites, and preserve Indian cultures from European influence. A number of such confederacies had been formed previously but had failed to hold together. Tecumseh ultimately allied with the British in their war against the U.S. and died in battle on October 5, 1813 at the Thames River in present-day Kent County, Ontario, fighting American soldiers who had invaded Canada. His confederation was the final one that posed a serious threat to American westward expansion.

Tecumseh was highly respected by many of the white men who fought with him and against him. Tecumseh's ally, British general Isaac Brock, stated in 1812 that Tecumseh "has the admiration of everyone who conversed with him." Major John Richardson, who became Canada's first novelist, called him "a savage such as civilization herself might not blush to acknowledge as her child." Michigan Territory Governor Lewis Cass, who led militia troops against Tecumseh, praised him as "remarkable in the highest degree" and characterized his oratory as "the utterance of a great mind roused by the strongest motives of which human nature is susceptible; and developing a power and a labor of reason, which commanded the admiration of the civilized, as justly as the confidence and pride of the savage." In journalistic accounts, Tecumseh was represented as an Indian Napoleon, Hannibal, and Alexander. Towns in Michigan, Nebraska, Kansas, Missouri, Indiana, Alabama, Oklahoma, and Ontario today bear his name.

Historians have attempted to account for the great admiration that whites had for Tecumseh. R. David Edmunds suggested that his "attempts at political and military unification seemed logical to both the British and the Americans, for it was what they would have done in his place." In addition, Edmunds proposed, "More than any other prominent Indian, Tecumseh exemplified the European or American concept of the 'noble savage,'" pointing specifically to his "kindness toward prisoners [that] particularly appealed to Americans." John Sugden listed qualities that Americans admired in Tecumseh: "courage, fortitude, ambition, generosity, humanity, eloquence, military skill, leadership . . . Above all, patriotism and a love of liberty." Richard White has noted the ironic nature of this admiration: "Tecumseh, the paradoxical nativist who had resisted the Americans, became the Indian who was virtually white."

Charles R. Sherman, the father of the future general, who settled in the Ohio Valley in 1811 and later became an Ohio State Supreme Court justice, was among the many admirers of Tecumseh. Lancaster, Ohio, where the general was born in 1820, is less than 40 miles northeast from the old Shawnee town of Chillicothe—just north of the present-day town of the same name— where historians believe that Tecumseh likely had been born some 55 years earlier. The Rev. P. C. Headley, in an 1865 biography of Sherman, one of at least five books about the general published since his military campaign of the previous year, quoted an unidentified person claiming to be from the area of the general's birthplace, who had written to Headley that Tecumseh "was for a long time kept in rather fond remembrance in this immediate vicinity, by those who were engaged in that conflict . . . because they knew that several times he prevented the shedding of innocent blood." The writer went on to relate that the desire of Sherman's father "to have one son educated for military life, led him to choose Tecumseh for the boy, he being born not long after the death of that chieftain."

Some 20 years later, Sherman himself, in the second edition of his memoirs—he had neglected to discuss his early life in the first edition— wrote that the War of 1812 "caused great alarm and distress in all Ohio." He stated, "Nearly every man had to be somewhat of a soldier, but I think my father was only a commissary; still, he seems to have caught a fancy for the great chief of the Shawnees, 'Tecumseh.'" When Sherman's older brother James was born, the general related, his father "insisted on engrafting the Indian name 'Tecumseh' on the usual family list." Sherman's mother, who had named her first son after a brother of hers, prevailed, however, in her desire to name her second son after a second brother of hers. By the time of his own birth, Sherman continued, "mother having no more brothers, my father succeeded in his original purpose, and named me William Tecumseh." As a boy, Sherman was called "Cump" by family members.

In 1872, William J. Reese, Sherman's brother-in-law, wrote that the choice of an Indian name did cause some consternation in the community. "Judge Sherman was remonstrated with, half in play and half in earnest, against perpetuating in his family this savage Indian name," Reese remembered. "He only replied, but it was with seriousness, 'Tecumseh was a great warrior' and the affair of the name was settled."

The oft-repeated use of the term "savage" in describing Tecumseh and Indians in general points to deeply rooted ideological ways of understanding cultural difference that whites at the time had even with respect to individuals such as Tecumseh, whom they clearly admired. Historian Robert F. Berkhofer has traced "persisting fundamental images and themes" of European understandings of Indians, noting the practice of "conceiving of Indians in terms of their deficiencies according to White ideals rather than in terms of their own various cultures." Whites, Berkhofer contended, often used "counterimages of themselves to describe Indians and the counterimages of Indians to describe themselves." The strength of such persistent dichotomies between savage Indians and civilized whites becomes even more noticeable in light of the irony that in the aftermath of the battle during which Tecumseh died, his corpse was scalped and pieces of skin were removed by American soldiers for souvenir strips and razor strops. Sudgen has written that "Henry Clay was said to have exhibited one in Washington the following winter."

The Treaty of Paris, adopted at the end of the French and Indian War (1754-1763), transferred control of Canada from France to Britain. After the United States later declared independence from Britain, France began offering secret support to the Patriots in the forms of arms, ammunition, economic aid, and technical assistance. Although the French government did not support Native Americans against the United States, some of the French Canadians (Canadiens) who had remained in Canada after the British takeover fought alongside Native American allies against the Patriots.

After acquiring Canada, the British had treated the Canadiens mildly. They allowed the former French citizens to continue practicing their Roman Catholic religion, and although the British required all residents of Canada to use the common law for public and criminal issues, they retained French civil law for private legal matters.

These measures helped the British to win the loyalty of many French Canadians. At the beginning of the Revolution, an American raid on Fort St. Jean, not far from Montreal, alarmed British officials and turned some Montreal residents against the Patriots. America’s wartime exclusion from the British fur trade benefited Montreal merchants, and despite lingering resentment over Britain’s possession of their colony, they decided that their own business interests lay with the preservation of British ties. Other French Canadians followed their religious and political leaders to the British side. Americans, after all, were the same people the Canadiens had just fought in the French and Indian War, when British New Englanders committed such atrocities as seizing farms, livestock, and produce, and stabling horses in their Catholic churches. Canadiens believed that they were better off with the British conquerors than with the American Revolutionaries.

In the territory bordering Canada and the new United States, the Six Nations of the Iroquois were also forced to make decisions with regard to alliances. Although many preferred to remain neutral, Tuscaroras and Oneidas generally chose to ally with the Americans. The rest of the Six Nations, led by the Mohawks, supported the British. Molly Brant, a respected Mohawk and mistress to British Indian Superintendent Sir William Johnson, and her brother Mohawk war chief Joseph Brant (Thayendanegea), convinced the Mohawk to side with the British. In several battles, Iroquois warriors, British regulars, and Canadien militia fought together to retain control over territory far down into Ohio Country and into the area around present-day Detroit.

Although some Canadiens fought with the British, others fought with the Patriots. For example, the 1st Canadian Regiment included Canadiens sympathetic to the American cause. They saw action in the Battles of Quebec (1775), Trois-Rivieres (1776), and Saratoga (1777), among others.