Complex sentence: At the start of the American Civil War Omohundro attempted to join his older brother Orville in the Confederate Army and was twice refused for his age but was allowed to serve as a courier at the headquarters of the Virginia Militia under Major General John B. Floyd.
Split into simpler sentences: At the start of the American Civil War, Omohundro attempted to join his older brother, Orville, in the Confederate Army. He was twice refused for his age, but was allowed to serve as a courier at the headquarters of the Virginia Militia under Major General John B. Floyd.