Final answer:
Colonel George Custer started the Battle of Little Bighorn by foolishly attacking a large group of Native Americans led by Sitting Bull.
Step-by-step explanation:
The Battle of Little Bighorn was started by Colonel George Custer, who led the U.S. Army's Seventh Cavalry in a foolish attack on a large group of Native Americans led by Sitting Bull.
Custer's personal ambition drove him to attack what he believed was a minor encampment, but instead, he encountered a force of nearly three thousand Lakotas, Cheyennes, and Arapahos. The Native American warriors surrounded and killed Custer and 262 of his men in the largest defeat of U.S. troops to a Native American force during westward expansion.