In compliance with the Aug revelation, Mormons engage in their first war-like confrontation in the so-called "Battle of Blue River," near Independence, Missouri. Led by Book of Mormon witness David Whitmer, the Mormons kill two mobbers. Of the one Mormon death during battle, the official History of the Church calls Andrew Barber "the first direct martyr to the cause," despite the previous murder of missionary Brackenbury.
The mobs, 40 or 50 with guns, begin their destruction. They meet 30 Mormons, with 17 guns, led by David Whitmer. At sunset there is a battle, and two of the Missourians are killed (including one who had claimed, "With ten fellows, I will wade to my knees in blood, but that I will drive the Mormons from Jackson County"). Andrew Barber is also shot and dies the next day. Philo Dibble is wounded and lies dying for several days until Newel Knight administers to him; then Dibble immediately vomits up several quarts of blood and the bullet with which he was wounded. That evening the Gilbert and Whitney store is totally demolished, and several of the Saints are advised to go to jail, as that is the only safe place in town. Later that night, however, they return home.
[Quinn, D. Michael, The Mormon Hierarchy: Origins of Power, Appendix 7: Selected Chronology of the Church of Jesus Christ of Latter-day Saints, 1830-47, http://amzn.to/origins-power; Conkling, Christopher J., Joseph Smith Chronology]