Complex sentence: Despite his Virginia upbringing, Strother supported the Union during the Civil War, Strother was commissioned by the U.S. Army and assigned as a topographer due to his detailed knowledge of the Shenandoah Valley.
Split into simpler sentences: Despite his Virginia upbringing, Strother supported the Union during the Civil War. Upon the war's outbreak, Strother was commissioned by the U.S. Army and assigned as a topographer due to his detailed knowledge of the Shenandoah Valley.