The election of Abraham Lincoln as U.S. President in 1860 polarized the country and the state. While a slave state, it had many Union sympathizers and active abolitionists. Theodore Charles Benteen, an ardent secessionist, vehemently opposed his son's associating with Unionists. A family crisis was ignited when Frederick joined the Union Army on September 1, 1861 as a first lieutenant in the 1st Missouri Volunteer Cavalry Regiment. (Len Eagleburger's book places Benteen at the Battle of Wilson's Creek in August 1861.) The 1st Missouri Volunteer Cavalry was often referred to as "Bowen's Battalion." It was later redesignated as the 9th and then merged into the 10th Missouri Cavalry.