Complex sentence: In late 1861 Rosecrans planned for a winter campaign that would capture the strategic town of Winchester, Virginia, turning the Confederate flank at Manassas, and he traveled to Washington to obtain McClellan's approval.
Split into simpler sentences: In late 1861, Rosecrans planned for a winter campaign to capture the strategic town of Winchester, Virginia, turning the Confederate flank at Manassas. He traveled to Washington to obtain McClellan's approval.