Complex sentence: They were the wealthiest of the Comanche in terms of horses and cattle, and they never once signed a peace treaty, and it was this faction of the Comanche that gave the American troops the most trouble during the Comanche Campaign.
Split into simpler sentences: They were the wealthiest of the Comanche in terms of horses and cattle, and they had never signed a peace treaty. It was this faction of the Comanche that gave the American troops the most trouble during the Comanche Campaign.