A call to arms to repel the invaders went out. The famed Nauvoo Legion was called to arms and began to stockpile munitions, drill, and build defenses. Meanwhile on the road to Utah, the Utah Expedition had it's original commander withdrawn and many of its troops to deal with "Bloody Kansas." The reduced force plodded forward and was strung out over miles of trail as its replacement leader, Albert Sidney Johnston, raced to catch up. He would not catch them until they already reached eastern Utah Territory (not far from Fort Bridger in modern Wyoming). The expedition had no orders anything like obliterating the Mormon Church and as they proceeded west escorted Mormon immigrants through hostile Indian territories.
When the expedition passed through the South Pass of the Rockies the trains were isolated and scattered over miles. Not being on a war footing they were not ready for what happened next. Governor Young issued the expedition an order to not enter Utah, a command that had no weight for Colonel Alexander, who commanded in Johnston's absence. Militia units were ordered to harass the army on the march and at South Pass raided an encampment of dragoons, running off some stock and apparently being complicit in a soldier perishing from a heart attack.
The scales finally fell off of Alexander's eyes and he recognized that he was facing an opposed entry into the territory. Alexander had to consolidate his scattered command and place them on a more defensible footing as winter was nigh. Hundreds of Mormons had perished just a year ago trying to pass through this same area as early winter storms trapped them.
Wagon trains were ordered to halt to await military escorts, which few of them had. Several of these trains were captured and burned by Lot Smith and his militia near the Big Sandy River. The image above shows a display at Ft. Leavenworth where it suggested that wagons such as this were burned at Simpson's Hollow. With further research it was found that the display does not contain an actual wagon from the event but a similar kind of wagon. (Darn.)
After burning wagon trains at a crossing of the Big Sandy, Lot Smith and his men came out of the mist at Simpson's Hollow and captured the trains there. Not a shot was fired. Yet traveling that area in the 1860s Sir Richard Burton noted Mormon children placing rows of crosses to mark the graves of the fallen in a tremendous battle. The embellishment and fabrication of aspects of the conflict appears to have a long tradition. There was no battle, tremendous or otherwise. It was a robbery. Smith took the supplies he needed, burned the rest, and sent the teamsters packing. He and his men could see a distant dragoon camp and believed that they had been spotted. They fled in haste and at a stopping point Lot determined to reload his pistols as the powder may have been wet by the heavy mist. The gun accidentally discharged piercing the clothing or flesh of three of his men (making Lot Smith the most dangerous man in the Utah War).
Johnston shortly thereafter joined his expedition and pushed it forward toward Great Salt Lake City. The expedition was halted in the passes by heavy snows and Johnston withdrew to camp for the winter in the vicinity of Fort Bridger. During the winter a peaceful settlement was negotiated and Federal troops marched through Great Salt Lake City in the spring. The Utah War was mostly a bloodless affair, with many perishing from disease and exposure but few due to mayhem. There is a story that a Utah militiaman came into possession of one of the military's Mississippi rifles and wanted to see how the weapon would perform against the Mormon fortifications on the approaches to Great Salt Lake City. He took the weapon to the canyon floor and one of his friends stood behind the stone wall, his head exposed. The militiaman at the bottom of the canyon fired, all in good sport, and, to his horror, splattered the head of his friend. The Mississippi rifles tend to overshoot when aimed level or downhill but are more accurate fired uphill.
On September 11, 1857 a related event happened near Cedar City at a place called the Mountain Meadows. There Utah militia surrounded and massacred a civilian train of emigrants killing over a hundred men, women, and children. The cover-up and subsequent attempts by apologist historians have done much to keep the issues of that day alive over 150 years later. But that is another story.