Complex sentence: The Indians in the camp had initiated peace negotiations with the U.S. army and believed they were under the protection of the army, but Colonel John Chivington and his force of 700 Colorado volunteers attacked the village and killed about 150 Indians, mostly women and children.
Split into simpler sentences: The Indians in the camp had initiated peace negotiations with the U.S. army and believed they were under the protection of the army. But, Colonel John Chivington and his force of 700 Colorado volunteers attacked the village and killed about 150 Indians, mostly women and children.