Just three decades after the United States broke free from Great Britain with the American Revolution, the two nations once again went to battle in the War of 1812. But this time, the combatants with the most at stake were arguably a third group: Native Americans.

At the time the war broke out, the young American nation had been aggressively expanding westward, putting Indigenous peoples and their ancestral homelands under relentless attack. Seeking military allies to help protect their territory, most Native Americans chose to fight on the side of the British. Indian warriors, many of whom rallied under the powerful and charismatic leader Tecumseh, played a crucial role in many battles.

An offshoot of a prolonged, bitter conflict between Great Britain and Napoleonic France, the War of 1812 pitted the naval superpower England against its former colony, a country in its veritable infancy. Post-independence, the relationship wasn’t going well. The U.S. chafed at Britain’s oppressive trade restrictions, designed to keep the fledgling nation from supporting the French war effort. Nor did Americans like how their merchant seamen were being abducted and forced into service for the British Royal Navy.

For its part, Great Britain sought to curb U.S. territorial growth—especially in the direction of Canada, its remaining colonial foothold on the North American continent. The British saw Indian territory as a crucial buffer against U.S. aggression and had already shown support to an increasingly militant tribal coalition along the Great Lakes frontier.

In June 1812, U.S. President James Madison signed a declaration of war against Britain, initiating the War of 1812. For Native peoples who had seen their homelands steadily usurped by white soldiers and settlers, the war would be their last, best chance for outside military help—and a decisive turning point in their struggle for sovereignty.

In the early years of the 19th century, Native Americans and First Nations people (Canada’s Indigenous populations) had to choose which powers to align themselves with and which to fight against. Atrocities committed against Native communities by U.S. settlers in the name of Manifest Destiny—the idea that God ordained them to spread democracy and capitalism across the “new” continent—predisposed many Native warriors toward the British.

After war was declared, the Shawnee chief Tecumseh quickly joined the fight, says Donald Fixico, distinguished foundation professor of history at Arizona State University.

Tecumseh, born in frontier territory in the Ohio Valley, had long held an open grudge against American military forces, who had killed both his father, Puckeshinwa, in 1774 and years later, his older brother and mentor Cheeseekau. As a teenager, Tecumseh joined his tribe’s war chief, Blue Jacket, to fight the U.S. Army. In 1791, Tecumseh helped defeat General Arthur St. Clair’s forces at the Battle of Wabash. But a decisive loss at Fallen Timbers in Northwest Ohio in 1794 resulted in a treaty forcing Indians to cede a major swath of territory from Ohio to Michigan. Tecumseh refused to sign, believing that no one tribe could own the land.

"Sell a country! Why not sell the air, the great sea, as well as the earth?,” he once proclaimed in a speech. “Did not the Great Spirit make them all for the use of his children? How can we have confidence in the white people…especially when such great acts of injustice have been committed by them upon our race?"

In 1808, along with his brother Tenskwatawa, Tecumseh founded Prophetstown, an Indigenous village (in present-day Indiana) centered on traditional Native values and lifeways. Hoping to unite Indigenous people against the invading white settlers, the Shawnee chief organized a multi-tribal alliance across the Ohio Valley. Seeking to expand it, he traveled widely among other tribes in the Great Lakes and Mississippi Valley, going as far north as Canada and as far south as the Gulf of Mexico. Using interpreters, the charismatic orator convinced many to set aside previous differences to unite against the imminent threat posed to their lands, their culture and their freedom.

According to Fixico, warriors from more than a dozen nations answered Tecumseh's call, from the Peoria and Ottawa in the North to the Muscogee and Creek in the South: “Even if you couldn’t understand his words, you could understand his feeling.”

All his passionate recruitment served Tecumseh well. On August 16, 1812, he and his Indian army joined British forces led by Sir Isaac Brock to deal a morale-crushing loss to the U.S. Army in their siege of Fort Detroit. The victory gave the British and their Indigenous allies firm control of the territory around the Great Lakes and pushed the frontier border back eastward—at least for a time.

After fighting several more battles alongside the British, including the ultimately unsuccessful siege of Fort Meigs in 1813, Tecumseh fell at the Battle of Thames.

General Isaac Brock, a British commander who had relied on Tecumseh’s support, said of the chief, “A more sagacious or a gallant warrior does not, I believe, exist.”

William Henry Harrison, who as governor of Indiana had squared off with Tecumseh in tense territorial negotiations—and later led U.S. soldiers to burn down Prophetstown in the famed Battle of Tippecanoe—had both fear and respect for the Shawnee chief. He called him “one of those uncommon geniuses, which spring up occasionally to produce revolutions and overturn the established order of things.”

Tecumseh’s death dealt a major blow to Native American morale and halted tribal momentum in resisting American westward expansion. Crestfallen by the leader’s death, many Native nations ceded their territories and relocated to government-imposed reservations. And as in previous and later wars, the cash-strapped American government, unable to pay its own soldiers, instead doled out parcels of formerly Native territory to white veterans in the form of land grants.

For many Native Americans from Canada to the Deep South, the war fomented disruption and division.

Early in the war, with much of Britain’s military busy fighting Napoleon’s troops, U.S. forces lost little time in attacking Canada. Unwillingly caught in the crossfire: the Mohawk community of Akwesasne, the only First Nations community that sits astride the U.S. and Canadian border along the St. Lawrence river. Their territory became the site of several skirmishes. And while some chose the American side of the conflict, many warriors from Akwesasne and the neighboring Kahnawake recruited by the British have been credited with helping prevent the U.S. conquest of Canada.

“Akwesasne was a strategic location for American and British forces,” writes historian Darren Bonaparte, tribal preservation officer for the St. Regis Mohawk tribe. “There were a number of individuals who ended up in the fight, some of them paying the ultimate price for doing so.”

Further south, in Alabama, the war bled into an intertribal conflict among the Creek. One faction, Red Sticks, had been inspired by Tecumseh to resist American intrusion, while another faction, the Lower Creek, generally supported the U.S. After the militant Red Sticks successfully attacked the American garrison at Fort Mims in 1813, killing hundreds, Major General Andrew Jackson and his 3,300-strong militia, which included some Cherokee and Lower Creek warriors, retaliated at the Battle of Horseshoe Bend, decimating several Red Stick towns.

The disaster effectively squashed Native resistance in the region. At the Treaty of Fort Jackson that followed, the Creek surrendered more than 20 million acres of their homelands, nearly half of today’s Alabama.

The final blow to Native people would come after the end of the war, during the signing of the Treaty of Ghent on December 24, 1814. With the conflict essentially ending in a draw, the Americans and British agreed to return to the prewar status quo. In doing so, the British abandoned their Native allies. Without financial and military backing, Indigenous resisters became far less successful in defending their homelands.

After the war, the United States began accelerating the pace of its treaties with various Indian nations—negotiating more than 200 agreements that resulted in the massive ceding of Native lands and the creation of reservations across the country. Those who didn’t willingly leave their ancestral homelands were forcibly removed and pushed into deadly journeys such as the Southern tribes’ Trail of Tears and the Navajo’s “long walk.”

As many historians have pointed out, with the War of 1812 ending in a draw, the conflict’s only real losers were the American Indians.