Complex sentence: The island was given to Great Britain by France at the end of the Seven Years' War in 1763 and in 1783, at the end of the American Revolution, Great Britain transferred the island to Spain.
Split into simpler sentences: The island was given to Great Britain by France at the end of the Seven Years' War in 1763. In 1783, at the end of the American Revolution, Great Britain transferred the island to Spain.