After slaughtering the Timpanogos and Utes in 1850, things didn't exactly get better between the Native peoples and the Mormon settlers. The Indians continued starving while the interlopers hoarded food and resources. There were skirmishes between the two sides, until finally on April 9, 1865, representatives of the Utes and the Mormons met to try and resolve their differences. However, according to Utah History Encyclopedia, an angry (and probably drunk) Latter-day Saint yanked a young chief off his horse. The Natives stormed off, vowing retaliation for the insult. And they meant it.
Over the next few days, Utes killed five Mormons and stole thousands of heads of cattle, led by a man known to the whites as Black Hawk. By the end of the year, thousands of more cows had been stolen, and 25 more settlers were dead. Eventually, that number would rise to 70 Mormon casualties.
The Latter-day Saints "considered themselves in a state of open warfare" with Black Hawk's followers and started killing Native Americans indiscriminately, even if they were from friendly tribes. The United States government, still suspicious of the Mormons, ignored their pleas for help, but it didn't tell them to stop killing Natives either, and hundreds died. The war raged for two years, until things started chilling out a bit in 1867, and a year later, Black Hawk signed a peace treaty, although hostilities between the two groups continued on and off until federal troops finally showed up in 1872. Even now, the Black Hawk War remains the "longest, costliest, and bloodiest" conflict in Utah's history.
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