The BEST description of Tecumseh's role in the War of 1812 is:
C. He tried to unify Native American tribes against the United States.
Tecumseh was a prominent Native American leader who sought to unite various tribes to resist the encroachment of settlers and the U.S. government on their lands. While he did have alliances with British forces against American expansion, his primary goal was to unite Native Americans in opposition to U.S. territorial expansion.