Though they're often overlooked by military historians – not Native American historians, mind you – the Plains Wars of the post-Civil War era saw some of the most brutal fighting between the American government and the Native American tribes fighting for their way of life. Eventually, the U.S. government was determined to move the native people to reservations. Those who did not sell their land were moved by force.
The fighting on the Plains saw the Battle of Little Bighorn, the massacre at Wounded Knee, and the Sand Creek Massacre, just to name some of the bloodiest moments. The fighting West of the Mississippi claimed countless lives, not to mention the end of the traditional ways for many Native Americans. Still, some fought back, with varying degrees of success.
An ally of the dreaded Comanche, the Kiowa were usually at war with anyone the Comanche went to war with, including the US Army. For 50 years, the Kiowa moved from the central United States westward to join the Comanche in raiding and trading from the American Southwest into Mexico, killing thousands. Even after most of the Kiowa moved to reservations in 1877, many warrior bands remained loose on the American frontier.
As more settlers rushed to the Rocky Mountains area, the area began to fill up with heavily-armed militias who would raid neighboring Arapaho and Cheyenne tribal settlements. In response, the Cheyenne began to fight back, forming different kinds of warrior bands, including the now-famous Dog Soldiers – warriors who would hold their ground, no matter what came at them. The Dog Soldiers rallied Cheyenne and Arapaho tribesmen together to wreak havoc on the Colorado ranching industry.
The Sioux were not the first tribe to fight the U.S. government, and they weren't the last, but they might be the most famous. The Sioux produced some of the most notable names and places in all the Indian Wars, including Little Bighorn, Custer's Last Stand, Red Cloud, Sitting Bull, and Crazy Horse, to name a few.
When the Army came upon bands of Sioux warriors, they didn't know if they would just be fighting the handful of warriors they saw or if another 5,000 to 7,000 were waiting somewhere they couldn't see.
If there's one thing the Union and Confederate Armies could agree on, it was fighting the Native American Apache tribes. In the early days of the Civil War, Confederate forces took on Apaches in the West before transferring to the actual Civil War they were needed to fight.
Clans of Apache rarely gathered in great numbers. They only did so in order to gather their forces to hit the U.S. Army in large formations. The US Army hated the Apaches so much, they would fight any sized organization they happened to come across, fearful of them massing numbers to form a war party. It took more than 20 years of concerted effort to end the Apache resistance.
The Comanches not only stymied the Army's effort to contain or destroy them, but they also took down other Native American tribes, eradicating them or driving them out of their traditional lands. The reason the Spanish Empire stopped expanding northward was because they were stopped by Comanches. The Texan Republic stopped expanding westward because of Comanches. The United States frontier actually receded because of the Comanches.
By the end of the 1860s, the men who won the Civil War for the Union were now running the country and President Grant, Commander of the U.S. Army William Tecumseh Sherman, and Gen. Philip Sheridan were determined to end the Comanche threat, finally subduing them with overwhelming force in 1875.