Frank Crawford Armstrong Frank Crawford Armstrong ( November 22 , 1835 – September 8 , 1909 ) was a United States Army cavalry officer and later a brigadier general in the Confederate States Army during the American Civil War . He is also known for being the only Confederate general to fight on both sides during the Civil War . Early life and Career . Armstrong was born on the Choctaw Agency in the Indian Territory , where his army officer father had been stationed . Armstrong ' s father , Francis Wells Armstrong , died three months before his son ' s birth . In 1854 , Armstrong ' s mother married Mexican - American War General Persifor Smith . In 1854 , Armstrong accompanied his stepfather on an expedition of the United States Army troops into the New Mexico Territory . His gallantry in a battle against Indians near Eagle Spring gained him a commission as a lieutenant in 1855 , following his graduation from Holy Cross Academy in Massachusetts . Armstrong then fought with Albert Sidney Johnston against the Mormons during the Utah War . Civil War service . By the time of the Civil War , Armstrong was a captain in the regular army . He led a company of Union cavalry at the First Battle of Bull Run . However , Armstrong resigned his commission and on August 10 , 1861 , he joined the Confederate Army . As Armstrong ' s Union resignation did not go into effect until August 13 , he was technically on both sides at the same time . He served as a staff officer under Confederate generals James M . McIntosh and Benjamin McCulloch before their deaths at the Battle of Pea Ridge , and was standing only feet away as McCulloch was killed . In 1863 Armstrong was elected as colonel of the 3rd Louisiana Infantry Regiment , and was soon given command of the cavalry of Major General Sterling Price . Two months later , he was promoted to brigadier general and commanded a cavalry division under Nathan Bedford Forrest at the Battle of Chickamauga . In February 1864 , Armstrong requested a transfer to the command of Maj . Gen . Stephen D . Lee . He was assigned command of a brigade of Mississippi cavalry previously led by Colonel Peter B . Starke . Armstrong and his men accompanied Lt . Gen . Leonidas Polk ' s corps to Georgia and served in the Atlanta Campaign , before participating in Lt . Gen . John B . Hood ' s disastrous campaign . He saw action during the campaign against Murfreesboro , and led much of Forrest ' s rear guard after the Hood ' s defeat at the Battle of Nashville . On March 23 , Armstrong was assigned to the defenses of Selma , Alabama , one of the Confederacy ' s last remaining industrial centers . On April 2 , 1865 , his troops participated in efforts to defend the town against a much larger Union force under Maj . Gen . James H . Wilson . Armstrong was captured later that day . Post - war years . With the return of peace Armstrong worked for the Overland Mail Service in Texas . Because of his frontier and military experience , he served as United States Indian Inspector from 1885 until 1889 , and was the Assistant Commissioner of Indian Affairs from 1893 to 1895 . Armstrong died in Bar Harbor , Maine in 1909 , and was buried in Rock Creek Cemetery in Washington , D . C . . He married Maria Polk Walker , daughter of Col . Joseph Knox Walker . Col . Walker is the brother of Lucius Marshall Walker , who also served as a Confederate general .