Complex sentence: The unified region collapsed in 1779, when the French recaptured Saint Louis and burned the major British settlement in the Gambia region, leading to the end of the unified region in 1783.
Split into simpler sentences: The unified region collapsed in 1779, when the French recaptured Saint Louis and burned the major British settlement in the Gambia region. This move by France led to the end of the unified region in 1783.