After the return from Florida, the Southern regiments were placed under the command of Major-General Benjamin Lincoln, from Massachusetts. Pinckney convinced Lincoln that as a Northerner, he needed an aide to assist him in relating to his Southern troops. Jackson was chosen for this position and was temporarily promoted to the rank of major. As Lincoln's aide he saw action in the Battle of Stono Ferry and the Siege of Savannah in 1779. In 1780 General Lincoln surrendered his troops after the lengthy Siege of Charleston. As a captured officer, Jackson was shipped to Philadelphia, then held by the British. After a few months he was returned to the Continental Army in an exchange of prisoners.