The Church of Jesus Christ of Latter-day Saints, often simply referred to as “LDS” or “Mormons,” has had a tumultuous relationship with the federal government, to say the least. But, in 1846, the members of the 16-year old denomination resided largely in Iowa, having migrated there from Nauvoo, Illinois, after a series of conflicts with the local inhabitants. The Nauvoo violence culminated in the murder of the church’s founder, Joseph Smith, and his brother Hyrum, leaving the leadership of the remaining devotees to Brigham Young. For his part, Young wished to fulfill one of Smith’s predictions and move the congregation to the Rocky Mountains, where he expected to find a site to establish a separate entity outside the boundaries of the United States. But, his flock had few resources and no ability to transport themselves outside the jurisdiction of the federal government—such a move would require crossing more than 1,000 miles, much of it arid and devoid of food resources, to establish a community that might also be subjected to attacks from hostile Native American groups in the region. Further, it would include crossing into territory belonging to the Mexican government, which was likely to prove significantly more hostile to their religious beliefs.
Coincidentally, the United States and Mexico had been sparring over the rightful boundary lines demarking the border between Texas and Mexico. The Mexican government insisted that the boundary should be the Nueces River, while the Texans (and by extension, the US) demanded all territory north of the Rio Grande. A series of skirmishes in the disputed area offered a harbinger of the conflict to come—and on April 23, Mexico declared war upon the United States, a move that was reciprocated by the U.S. Congress two days later. The U.S. Army, which had functioned as a frontier constabulary for much of the preceding three decades, was in no way prepared to undertake major operations on foreign soil—and as such, the government began enlisting volunteer recruits from any sources that it could find.
In early June, President James K. Polk authorized Colonel Stephen Kearny to recruit up to 500 Mormon volunteers for service during the war. In turn, Kearny dispatched Captain James Allen, a graduate of the West Point class of 1829, to the Mormon camp at Mosquito Creek, Iowa. Assuming Allen could persuade 500 men to volunteer under the standard terms of service, he would be promoted two ranks to lieutenant colonel, and named the commander of the newly-formed battalion. At first, Allen’s efforts proved fruitless—the Mormon men did not trust the government, and had little affection for Allen, who in turn disdained their faith and understood little of their motivations. But, when Brigham Young considered the situation, and determined that it would be in the church’s best interest to participate, the situation changed.
Young knew that his followers had insufficient resources to make the trek across the plains to reach his presumed haven in the Rocky Mountains. Joining the Army for the move would ensure that 500 of his followers could serve as the advance party, while relying upon Army logistics for their own sustenance. Further, those men would be armed and equipped by the government, and allowed to keep all of the provided items at the end of their service. And, in perhaps the most important governing factor, each man was authorized an immediate clothing allowance of $42, in cash, payable upon signing the articles of enlistment. Young implored his followers to join the unit, donate the payment to the church to allow the purchase of the necessary items to move the remainder of the congregation westward, and to blaze the trail to their new home.
Having received Young’s blessing and earnest support, Allen soon reached his enlistment goals and commenced the movement of his unit westward. Their first stop was at Fort Leavenworth, Kansas, where they picked up the trail of Kearny’s unit, which had headed southwest toward Santa Fe. At Fort Leavenworth, the so-called Mormon Battalion was formed into companies, received their equipment and allowances, and began learning the rudiments of military drill and discipline. Because Kearny had already headed west without the Mormons, Allen elected to continue training his battalion on the march to Santa Fe, and ordered them to depart Fort Leavenworth after only two weeks of instruction. The unit began its march toward Santa Fe without its commander—Allen had fallen ill, and ordered them to leave him behind. On August 23, Allen died, and was the first man buried in the Fort Leavenworth military cemetery—under a headstone bearing his new rank. The men of his battalion, who had initially so disliked the young officer, deeply mourned his loss—but vowed to press on in their journey under Captain Philip St. George Cooke.
The Mormon Battalion never fought a battle during the Mexican War. The closest they came to firing their weapons in anger came in November 1846, when they encountered a herd of wild cattle and had to shoot some of the bulls to turn a stampede. Instead, the Mormon Battalion primarily worked to build a road from Santa Fe to California, facilitating the travel of hundreds of thousands of migrants in the succeeding decades. In late January 1847, they finally reached San Diego, after a march of nearly 2,000 miles. They spent the remainder of their enlistment period as occupation troops in San Diego and Los Angeles. In the meantime, Brigham Young, using funds provided by the members of the battalion, led his congregation westward, settling in the Great Salt Lake valley in modern Utah. When the battalion’s period of enlistment ended in July 1847, most of the members joined the rest of the Mormon migrants in Utah, although a few remained in California, earning additional money to support the new settlement.
The legacy of the Mormon Battalion is somewhat difficult to pin down. Some members of the LDS see it as another example of mistreatment by the U.S. government, and argue that the church should have received government support for its migration without conditions of military service. Others see it as an example of two organizations existing in a symbiotic relationship that benefits both, without requiring that their goals be particularly similar. The battalion remains the only religion-based unit ever mustered into service in the U.S. Army. Its construction efforts significantly improved the prospects of migrants seeking to move from the plains to the California coast. But, the cooperative relationship between the Mormons and the U.S. Army did not last long—barely a decade later, the Army carried out an invasion of Utah as a mechanism of demonstrating federal dominance over the territory.