By Shreeg88 at English Wikipedia, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=10542884

In July 1742, decisive battles between the Spanish and British took place in and around St Simons Island, Georgia. It was the culmination of a conflict which began when the British invaded Florida, partly because of the number of runaway slaves that had come to the Spanish colonies.

In the late 1600’s Spain began offering asylum for runaway slaves from the English colonies to the north.  The condition of asylum was conversion to Catholicism and service to Spain. The Spanish were interested in destabilizing the English colonies to the north, scuttling the economy. The easiest and most logical way to do this would be to break the backs of the southern plantation economy by inviting slaves to flee to safer ground.

By 1700, Florida was a prosperous Spanish colony probably as economically well-off as any English one to the north.

In 1704, during Queen Anne’s War The British invaded Spanish Florida from the Carolina’s. The Carolina-based English colonists and their native American allies invaded Spanish-held Florida. Former Carolina Governor James Moore led the invasion on behalf of the English colonists. They were resisted by the Apalachee Indians who resided in the Big Bend region and were allies of the Spanish crown. Florida was left devastated by the war and according to some historians never really recovered until the 1770’s by which time the colony was under British rule and enjoying a renaissance due to the fleeing of loyalists from the Thirteen Colonies.

Wikipedia described the Florida front as follows:

Spanish Florida and the English Province of Carolina were each subjected to attacks from the other, and the English engaged the French based at Mobile in what was essentially a proxy war involving primarily allied Indians on both sides. The southern war, although it did not result in significant territorial changes, had the effect of nearly wiping out the Indian population of Spanish Florida, including parts of present-day southern Georgia, and destroying Spain’s network of missions in the area.

The most important battle of the conflict took place in 1704 at Ayubale. Wikipedia has a great write up on the battle which was a decisive victory for the English and its allied Indian tribes and .half the resisting Apalachee Indians were killed or captured.

In 1738, Fort Mose was established two miles north of St Augustine – A village to defend St Augustine that also was operated by free blacks – by 1740 the town had a population of 100 within its walls and was governed by a European of African descent. Fort Mose was the first legally sanctioned free African settlement in what would become the US.

In 1739, the War of Jenkins Ear which was essentially the North American theater of the War of Austrian Succession broke out. By 1740, Britain (England and Scotland were formally united by the Act of Union in 1707) felt they could knock Spain out of the American part of the war by capturing St Augustine. So in 1740 James Oglethorpe the founder of Georgia seven years earlier, and the colonies Governor led an overland invasion force into Spanish Florida. The establishment of the Georgia Colony by Oglethorpe had given the British a beachhead from which to invade Florida.

On his way to St Augustine, Oglethorpe captured Fort Mose. The residents had mostly been runaway slaves from the British colonies. When the British captured Fort Mose, the free black residents fled to St Augustine where they played a critical role in the city defense.

Oglethorpe and his British forces began the siege of St Augustine on June 13th, 1740. The Spanish decided while St Augustine was under siege to launch a counter-offensive aimed at Fort Mose where the British had left behind a garrison. The Spanish and free black forces liberated Fort Mose and within weeks a Spanish fleet from Havana had reached St Augustine prompting a British withdrawal back to Savannah.

In 1742, Spanish forces numbering about 5,000 invaded Georgia from Florida and marched toward Savannah. This month in 1742- 250 years ago, the Spanish were defeated at St Simons Island. In the subsequent peace treaty the Florida-Georgia border was fixed to St Mary’s River where it remains today.

More on the decisive battle here.