Why did Tecumseh the Shawnee chief resort to an alliance with the British?

Tecumseh, the Shawnee chief, sought an alliance with the British primarily to counter the westward expansion of American settlers, which threatened Native American lands and cultures. He believed that uniting various Indigenous tribes under a single confederation would strengthen their position against American encroachment. The British, who were keen on undermining American territorial ambitions, offered support and resources, making the alliance appealing for Tecumseh in his quest to protect his people's sovereignty.