On April 20, 1779, Gen. Benjamin Lincoln moved the bulk of his forces from Purrysburg towards Augusta, in an attempt to get into Savannah from the back door. He took with him 3,000 men, leaving roughly 1,200, mostly South Carolina militia, under Col. William Moultrie in the Beaufort District. Moultrie's command was scattered - he was at Black Swamp with half the militia forces, while Lt. Col. Alexander McIntosh of the SC 2nd Regiment remained at Purrysburg with the other half.

British Gen. Augustine Prevost recognized the Patriots' weaknesses and on the night of April 28th, he crossed the Savannah River "at a spot so difficult as to completely surprise the enemy." This proved successful. Lt. Col. McIntosh quickly retreated out of Purrysburg, and Col. Moultrie joined up with him at Coosawhatchie on May 1st. He moved the bulk of his army to Tullifinny Hill and left about 100 men at the Coosawhatchie Bridge.

When word arrived that Gen. Prevost was approaching, Col. Moultrie dispatched 350 men to protect the retreat of those at the Coosawhatchie Bridge - Lt. Col. John Laurens volunteered to lead this detachment, with Maj. John Barnwell, Jr. and Capt. William Hazzard Wigg along with a cavalry detachment from the Beaufort District.

May 3 - Battle of Coosawhatchie.

May 4 - Battle of Tullifinny Hill.

Col. Moultrie accepted the fact that Gen. Prevost had him greatly outnumbered and sent word to Gen. Benjamin Lincoln to quickly return to South Carolina and assist him in preventing Charleston from falling. Moultrie crossed the Combahee River at the Salkehatchie Bridge and made camp at the Salkehatchie Chapel in Colleton County. Moultrie reported that the local militia was so discouraged that they had deserted his command "to take care of their families and property which is a very natural consequence."

Col. Moultre began retreating further, felling trees and destroying bridges to slow Gen. Prevost's pursuit. Repeated messages to Gen. Lincoln went unanswered. Moultrie estimated that his dwindling command was opposing more than 3,000 British troops. On May 6, he retreated to Jacksonborough, and by May 8th had reached the edge of Charleston.

May 7 - Fishpond Bridge.

Prevost's march through the lowcountry was particularly destructive. His regulars of the 71st Regiment and the 60th Regiment were accompanied by a large group of Loyalist militia and swarming bands of Indians. His forces managed to induce hundred, perhaps thousands, of lowcountry slaves to leave their plantations with false promises of freedom.

On May 8th, Lt. Col. Casimir Pulaski and his Legion of cavalry arrived from the north. Lt. Col. Francis Marion moved his regiment from Fort Moultrie to the west side of Charleston. On May 9th, Governor John Rutledge and 600 backcountry militia arrived from Orangeburgh.

By the time that Col. Moultrie left Fort Dorchester and arrived near Charleston on May 9th, he barely had 600 men with arms. Among them were Capt. Robert Barnwell, commanding the remnants of the Beaufort Militia, and Maj. John Barnwell, in command of twenty horsemen, the only cavalry remaining in Moultrie's command. Fully half of the militia had abandoned the Patriots on the retreat. But, Moultrie's stalling tactics proved a godsend.

Prevost crossed the Ashley River Ferry on May 10th, and arrived at Charleston Neck on May 11th. Gov. Rutledge sent a delegation to Prevost "discuss terms" - a mere stalling tactic on the Patriot's side - but Prevost wanted nothing of it. Via a different route, Gen. Benjamin Lincoln made a hasty march with over 4,000 men and arrived at Col. Moultrie's position on Charleston Neck the evening after Gen. Prevost had arrived. Prevost soon realized that his retreat may be in jeopardy, and he decided to withdraw from his precarious position.

On May 11th, Maj. Benjamin Huger and many of his twelve-man team were accidentally killed by friendly fire while attempting to close a gap in the abatis around Charleston.

Since Gen. Prevost had such a large number of men, his retreat would not be a quick one, and he too had to use stalling tactics.

May 20 - Matthew's Plantation.

June 20 - Stono Ferry.

Gen. Prevost decided to abandon John's Island and retire down the coast to Beaufort. He was now faced with difficult logistical problems, a shortage of supplies, and his troops hadn't been paid in months. Prevost repeatedly urged Maj. Gen. Henry Clinton to provide naval support to assist in withdrawing his men, but it was not to come.

He began to retreat through the sea islands to Beaufort, a remarkable military maneuver. Prevost had to transport his army, including cavaly and artillery, across four large tidal rivers in addition to the broad and treacherous St. Helena Sound. The army had to cross the North Edisto River to Edisto Island and the South Edisto River to Otter Island. From there, they traversed the broad St. Helena Sound. Half of his forces went directly across the sound to Coffin Point to secure St. Helena's Island. The other half proceeded up the Coosaw River to Sam's Point and thence across Lady's Island to the Whitehall Ferry. There, they crossed the Beaufort River and occupied the town of Beaufort on July 8th.

While retreating through the sea islands, the soldiers and their auxiliaries had continued to plunder the neighboring plantations, and the weight of the booty slowed their movements. In addition, thousands of runaway slaves had attached themselves to the British army in hopes of freedom.

Gen. Prevost found the quiet town of Beaufort to his liking. Besides having easy access to Savannah, his headquarters, the sea islands were considered the most favorable part of the lowcountry. Prevost decided to leave Lt. Col. Maitland and the light infantry for the defense of Beaufort and the other sea islands, and he boarded a ship for Savannah.