On August 12 disaster struck in the form of a hurricane. For two days the storm raged on, unabated. Both fleets sustained heavy damage. Two of the French ships lost their masts and many vessels were so severely damaged that their ability to engage in warfare was questionable.
On the land, the hurricane was no less severe. Trees were uprooted, tents were blown and provisions were destroyed. Ammunition was so wet that it was useless, and soldiers were exposed to heavy rain for hours on end. Both sides suffered, but when the storm abated the British were able to reform and set up a defense line across the island from Tonomy Hill to Easton's Beach. The Americans found themselves extremely short on provisions and unable to get more from the mainland because of the storm.
On Aug. 17, Sullivan was established two miles north of the British lines and began his artillery barrage feeling that the French would return momentarily to proceed as planned. On Aug. 20, D'Estaing informed them that instead of partaking in the battle he was going to Boston to refit his ships. The French commander had received word that more ships were on the way to America from England. Fearing an encounter with the British with his damaged vessels, he resisted the pleading of Greene and Lafayette and left Rhode Island on Aug. 21.
Without the French troops and cannon, Sullivan could not launch a frontal attack. Greene wanted to lead a surprise attack at Pigot's right rear with longboats from the sea, but Sullivan rejected it as too risky without the French fleet for protection. Many militias, angered by the delay and the French action, began to leave the island. The entire New Hampshire militia withdrew and were followed shortly thereafter by half the Rhode Island and Massachusetts militia, including John Hancock, who went to Boston to speed up the refitting of the French fleet.
By Aug. 27 Sullivan was left with little more than 5,000 troops. Fearing that Pigot would realize his advantage and attack, he made plans for a retreat. On the night of Aug. 28, the Americans began a quiet orderly withdrawal from their positions. Lafayette hurried to Boston to try to persuade D'Estaing to return before the Americans were forced to leave.
At daybreak on Aug. 29, General Pigot became aware of the American action and set out in pursuit. The Americans stopped at Butt's Hill with flanks protected by Colonel Livingston with a light corps on the east road, and Colonel Laurens and Major Talbot on the west road. The British established contact at about 7 a.m. Skirmishes continued steadily as the Americans withdrew in orderly fashion, leading the British toward the meadow selected by Sullivan to fight a rear-guard action.
The American plan worked well. Major Silas Talbot hid his men behind low stonewalls in the hope of an ambush. The British 22nd Regiment led by Colonel Campbell came right into the trap. Talbot waited until they were right up to the wall and then his men rose as one and poured a deadly volley into the Redcoats. Before the confused troops could retaliate, a second volley was fired, killing off one-fourth of the regiment and sent the remainder running away.
By 9 o'clock on Aug. 29, fighting was intense all along the American line. As was feared, British naval vessels appeared and began shelling. By 10 o’clock the British charged the American lines twice and were beaten back. The third attempt was the heaviest. Nathanael Greene commanded the right wing, which bore the brunt of the British and Hessian attack. The American troops here included James Varnum's Continental Infantrymen and Cornell's brigade of Rhode Island regiment, which included black and Indian troops. These troops, under Major Samuel Ward Jonathan Arnold, met the concentrated attacks of the Hessians on three separate occasions, and both sides suffered heavy casualties after ferocious hand-to-hand combat.
This regiment was the only one of its type in the Revolutionary War. The idea of using freed slaves came from James Varnum, who persuaded the General Assembly to free those who would volunteer to fight on the rebel side and to pay the masters who freed them. These black volunteers proved to be among the best troops at the battle and their efforts against the Hessians helped to save the American army.