Final answer:
The Texas Rangers had several duties, not just protecting settlers from Native American attacks, including law enforcement, military engagements, and maintaining order during the western expansion.
Step-by-step explanation:
The main duty of the Texas Rangers was not solely to protect settlers from attacks by Native Americans. While this duty was certainly a significant aspect of their role in the 19th and early 20th centuries, their responsibilities were more diverse.
The Texas Rangers were established to serve as a paramilitary force to enforce the law and maintain order, which included a range of activities such as capturing criminals, participating in battle during the Texas Revolution, and protecting the state's border. However, they were also involved in violent confrontations with Native American tribes, Mexican Americans, and during various other conflicts that arose as American settlers expanded westward.