Final answer:
During the Civil War, the Comanche people were able to expand their influence as the Union's military presence in the Indian Territory diminished, which allowed them to assert themselves against both the settlers and other Native American tribes.
Step-by-step explanation:
The Civil War created new opportunities for the Comanche people as it caused political upheaval among the tribes, and notably, with the Union withdrawing from Indian Territory, it gave certain Native American groups like the Comanche a chance to expand their influence. For example, the Comanche, who had adopted the Spanish horses, transformed into a powerful group capable of negotiating with European powers. Additionally, the Homestead Act and other laws passed during the Civil War era encouraged the settlement of the West with non-slaveholding whites, leading to further expansion and conflicts but also bringing new dynamics of power where groups like the Comanche could potentially exploit.
As the conflict between the Union and Confederate forces escalated, the power vacuum allowed groups like the Comanche to assert themselves more forcefully in regions where U.S. military presence had diminished. Their mastery of horseback riding and warfare gave them an advantage in these territories. However, ongoing settlement and conflict would continue to shape their fortunes.