Utah War

The Utah War (1857–1858), also known as the Utah Expedition,  or the Mormon Rebellion was an armed confrontation between Mormon settlers in the Utah Territory and the armed forces of the US government. The confrontation lasted from May 1857 to July 1858. There were some casualties, most of which were non-Mormon civilians. The war had no notable military battles.

In 1857–58, PresidentJames Buchanan sent U.S. forces to the Utah Territory in what became known as the Utah Expedition. The Mormons, fearful that the large U.S. military force had been sent to annihilate them and having faced persecution in other areas, made preparations for defense.

Rather than engaging the Army directly, Mormon strategy was one of hindering and weakening them. The Mormons blocked the army’s entrance into the Salt Lake Valley, and weakened the U.S. Army by hindering them from receiving provisions.

The confrontation between the Mormon militia, called the Nauvoo Legion, and the U.S. Army involved some destruction of property and a few brief skirmishes in what is today southwestern Wyoming, but no battles occurred between the contending military forces.

At the height of the tensions, on September 11, 1857, between 95 and 120 California-bound settlers from Arkansas, Missouri and other states, including unarmed men, women and children, were killed in remote southwestern Utah by a group of local Mormon militia. They first claimed that the migrants were killed by Indians but it was proven otherwise. This event was later called the Mountain Meadows Massacre.

Source : Wikepedia