In 1778, Pinckney and his regiment, returning to the South, took part in a failed American expedition attempting to seize British East Florida. The expedition ended due to severe logistical difficulties and a British victory in the Battle of Alligator Bridge. Later that year, the British Army shifted its focus to the Southern theater, capturing Savannah, Georgia, in December 1778. In October 1779, the Southern army of Major General Benjamin Lincoln, with Pinckney leading one of its brigades, attempted to re-take the city in the Siege of Savannah. This attack was disaster for the Americans, who suffered numerous casualties.