Under the Banner of Heaven by Jon Krakauer, 2003, Excerpts
Alleging that the Mormons had committed a long list of treasonous acts, in May 1857 Buchanan dispatched a contingent of federal officials to restore the rule of law in Utah, including a new territorial governor to replace Brigham Young. More ominously, the new president ordered twenty-five hundred heavily armed soldiers to escort these officials into Salt Lake City and subdue the Saints if necessary. For all intents and purposes, the United States had declared war on the Mormons.
It turned out to be a war that generated much more smoke than heat, and a concord was ultimately negotiated before the Saints and American soldiers exchanged a single shot. Brigham had actually been aware for more than a month that federal troops were in route to Utah, but had withheld the news until Pioneer Day for maximum dramatic effect. For the better part of a year, in fact, he’d been stockpiling arms and drilling his crack militia. The Nauvoo Legion.
While they awaited the arrival of the federal army, Brigham and other church leaders did their utmost to inflame passions against the Gentiles. The Saints were reminded again and again of the murders of so many of their brethren in Missouri and Illinois, and how their beloved prophet, Joseph Smith, had been shot dead by a godless mob in Hancock County. Rumors were spread that the approaching troop had orders to hang Brigham and exterminate the Mormons altogether.
President James Buchanan (left) sent federal troops to replace Brigham Young (right) as governor of the Utah territory.