Why did general charles cornwallies retreat from the carolines and march north into virgina

His counter-insurgency campaign in the Carolinas was unsuccessful and his army had taken serious casualties. The Americans had successfully put down the Loyalist elements in the area. Cornwallis and his troops had marches to Wilmington. He had taken a serious hit at Guilford Courthouse and elsewhere, and much of his army was sick or wounded. Everywhere in the area, the Americans had gained strength. Loyalist supporters in the area were defeated and dispersed by the Americans.