Complex sentence: He learned of the outbreak of the Civil War while serving as a captain in California and, despite believing strongly that the Union should not be dissolved, he returned to Virginia to fight for his native state and the Confederacy.
Split into simpler sentences: He learned of the outbreak of the Civil War while serving as a captain in California. Despite believing strongly that the Union should not be dissolved, he returned to Virginia to fight for his native state and the Confederacy.