Complex sentence: Chief Yene-wood being dishonored before his people saw it as the final blow of a long endurance of insults and depredations over nearly 30 years that rallied the Utes under the leadership of Chief Black Hawk to declare war against the Mormons.
Split into simpler sentences: Chief Yene-wood had been dishonored before his people and saw it as the final straw in a long series of insults and depredations over nearly 30 years. He rallied the Utes under the leadership of Chief Black Hawk to declare war against the Mormons.