Notable early instances of use included the Battle of Hoover's Gap (where Colonel John T. Wilder's "Lightning Brigade" of mounted infantry effectively demonstrated the firepower of repeaters), and the Gettysburg Campaign, where two regiments of the Michigan Brigade (under Brigadier General George Armstrong Custer) carried them at the Battle of Hanover and at East Cavalry Field. As the war progressed, Spencers were carried by a number of Union cavalry and mounted infantry regiments and provided the Union army with a firepower advantage over their Confederate opponents. At the Battle of Nashville, 9,000 mounted infantrymen armed with the Spencer, under the command of Maj. Gen. James H. Wilson, chief of cavalry for the Military Division of the Mississippi, rode around Gen. Hood's left flank and attacked from the rear. President Lincoln's assassin John Wilkes Booth was armed with a Spencer carbine at the time he was captured and killed.