The Battle of Belmont was fought on November 7, 1861, in Mississippi County, Missouri. It was the first combat test in the American Civil War for Brig. Gen. Ulysses S. Grant, the future Union Army general in chief and eventual U.S. president, who was fighting Major General Leonidas Polk. Grant's troops in this battle were the "nucleus" of what would become the Union Army of the Tennessee.

The Army of the Tennessee was a Union army in the Western Theater of the American Civil War, named for the Tennessee River. A 2005 study of the army states that it "was present at most of the great battles that became turning points of the war—Fort Donelson, Vicksburg, and Atlanta" and "won the decisive battles in the decisive theater of the war."