Georgia President Button Gwinnett has organized an expedition against the capital of British East Florida, St. Augustine, following the raiding expedition by Loyalist Thomas Brown in February 1777 against his state.

General Robert Howe, commander of the Continental Army's Southern Department, agrees to contribute some Continental forces, and authorizes Colonel Samuel Elbert's 2nd Georgia Regiment and Brigadier General Lachlan McIntosh to participate.

McIntosh and Gwinnett are bitter political enemies, and cannot agree on issues of command and strategy.

As a consequence, Howe and the Georgia legislature give command of the operation to Colonel Elbert. (Another consequence of the disagreement between McIntosh and Gwinnett is a duel they fought on May 16; both men are wounded, and Gwinnett will die several days later.)

In addition to the three hundred Continentals from the 1st and 2nd Georgia Regiments, the expedition includes some militia cavalry led by Colonel John Baker.

Sources vary on the exact size of Baker's company; it is reported to be either about one hundred or two hundred men.

The expedition had left Sunbury on May 1.

Baker's cavalry rides overland while Elbert's Continentals sail via the inland waterway with the expectation of meeting at Sawpit Bluff, near the mouth of the Nassau River in what is now Duval County, Florida.

Baker reaches Sawpit Bluff on May 12.

The flotilla, under the command of Commodore Oliver Bowen, has been delayed by contrary winds, and will not reach Amelia Island until May 18.

East Florida Governor Patrick Tonyn had been alerted to the Georgia plans in April, and reports that Baker's company had crossed the St. Marys River on May 10.

A mixed band of Loyalist rangers and primarily Creeks led by Lieutenant Colonel Brown had continued to be active on the border between the two provinces after the February raid; they discover Baker's camp.

Brown wants to capture one of the Georgians for questioning, but Baker's patrols are vigilant and the party sent for the purpose is fired on.

On the night of May 14–15 Brown sends fifteen natives to steal Baker's horses.

They successfully take some of Baker's horses (sources disagree on the exact number, suggesting either forty or one hundred), but are chased down by Baker's men.

In the ensuing skirmish the horses are recovered; however, at least one native (a Chiaha) is killed, and his body is reported by the British to be mutilated by the Georgians.

Governor Tonyn's report of the action, written on June 18, will note that this "greatly exasperated the Savages", which would prove to have disastrous consequences for the Americans.

Worried about the delay of Elbert's force, and having learned from a local resident that authorities had been alerted to the expedition, Baker moves west to find a better strategic location to wait, and encamps on the banks of Thomas Creek, a tributary of the Nassau River.

Meanwhile, Brown's natives and rangers have been reinforced by British regulars under the command of Major Mark Prevost, bringing their total force size to about two hundred.

Their scouts locate the American camp on the night of May 16–17.

Brown's natives and rangers set up an ambush ahead of Baker's route, while Prevost's regulars advance in three columns behind Baker.

When Baker's column reaches the ambush around 9:00 am, Brown's men deliver a surprise volley at fifty yards (forty-six meters) from the front and flank.

Baker and his men turn to flee, directly into Prevost's oncoming regulars.

The Patriots, already shaken, are quickly overwhelmed by the large numbers of rangers and natives appearing in the underbrush.

About half of the Georgians flee at first sight of the enemy; Baker, his horse taken by one of his companions, escapes into the swamps.

Casualty reports from the encounter vary.

David Russell reports that three Georgians were killed, nine wounded, and thirty-one captured, and that many of the captured were later killed by vengeful Creeks.

Charles Jones reports similar numbers, except that thirty-four were taken prisoner, a captive count echoed by William Nester.

Edward Cashin claims that forty prisoners were taken, of whom sixteen survived Creek vengeance.

The National Park Service account of the battle says that eight were killed in the battle, nine wounded, and  thirty-one captured, of whom fifteen are later killed.

Neither Governor Tonyn nor Lieutenant Colonel Brown report any casualties on their side.

The British, despite the defeat at Saratoga, turn their attention in 1778 to reconquering the South.

Prominent Loyalists with great influence in London have persuaded the British that Loyalist support is high in the South, and that a campaign there will inspire a popular Loyalist uprising.

The British center their strategy upon this thinking.

A southern campaign also has the advantage of keeping the Royal Navy closer to the Caribbean, where it will be needed to defend lucrative colonies against the Franco-Spanish fleets.

On December 29, 1778, an expeditionary corps from New York captured Savannah.

British troops now move inland to recruit Loyalist support.