November 1779 saw all the companies of the regiment being transferred to the Southern theatre of operations. In April 1780 the 64th was part of the covering force besieging Charleston, while the grenadier and light companies formed part of the main siege force. After the capture of Charleston, the grenadier and light companies were withdrawn to New York and as Major-General Cornwallis began to advance on Virginia, the 64th remained in Carolina as guard troops. In 1781 the 64th were involved in the Battle of Eutaw Springs and a year later in one of the last actions of the war, the Battle of the Combahee River. The grenadier company was reunited with the 64th but the light company was among the units that surrendered with Cornwallis at Yorktown.